Krell

"The ORIGINAL" - World Leading, class-A, iBias Amplifiers, AV Processor & Streamer DAC- made in the USA
The Leader in Audio Engineering

It's hard to overstate the importance of Krell Industries in the history of high-end audio. Founded in 1980, Krell was the audio equivalent of Lamborghini—an audacious riposte to more Ferrari-like rivals such as Mark Levinson and Audio Research. For almost four decades, Krell has gone on from strength to strength, introducing a stream of ever more ambitious products that tested the depth of their customers' pockets, along with the strength of their audio equipment shelving.  With their new iBias class-A design and new products, Krell has reestablish its brand once again as a world leader in the high-end audio market. 

Krell amplifiers have always been overstated in design and understated in their on-paper specifications. Back in the 1980s, we would talk about “Krell watts,” where the amp's massive power supply and conservative on-paper power rating meant that it could drive speakers in real world systems way beyond what the numbers would suggest.

KRELL'S NEW XD SERIES WITH ENHANCED CLASS-A, iBIAS TECHNOLOGY:
Krell's history is rich with breakthrough Class A amplifiers that have helped build the Krell legacy of offering the best sounding amplifiers available. Audiophiles have always considered Class A technology to be the best sounding operating state for amplifiers. However, despite Class A's unrivaled sound quality, it has fallen out of fashion because of recent demands to reduce power consumption and heat in home electronics products. Krell engineering took this challenge and redefined the meaning of high performance power amplifier. Our goal - unmatched performance, elegant design, and a compelling array of features. The breakthrough - a patent pending circuit delivering Class A operation without the excessive heat and wasted energy of conventional designs, housed in a striking new form factor, with network connectivity for advanced access and monitoring. The sound is open and unconstrained, in a manner that rivals live performance and the true sound of voices and instruments. Music and dialogue are reproduced with a richness, detail, and startling dynamics that fill a room.

Plainly stated, Class A designs are the most musically accurate circuit topology available. Class A amplifiers do not suffer from the inherent distortions that all Class AB amplifiers experience. In a traditional Class A design, the output transistors conduct full current at all times regardless of the actual demand from the speakers. Often, only a fraction of this power is needed to reproduce an audio signal at normal listening levels. The rest of the power is dissipated through the amplifier’s heat sinks, producing large amounts of wasted heat. With Krell's iBias™ technology, bias is dynamically adjusted, so the output transistors receive exactly as much power - but only as much power - as they need.
Krell's iBias Class A technology allows our latest amplifiers to run in full Class A mode to full power while minimizing heat generation. Previous efforts at using a "tracking" bias, while effective, only measured the incoming signal and set bias levels from this information. Our new patent pending iBias technology significantly elevates the effectiveness of previous designs by calculating bias from the output stage. This seemingly small change in topology results in a dramatic improvement in sound quality, especially midrange richness and purity.

The core of the technology is an innovative, patent pending design for a dynamic intelligent bias circuit. Our iBias Class A circuit directly measures the output current of the amplifier and adjusts the bias to the optimum level. Because iBias Class A measures the output current, the real time demands of the specific speaker connected to the amp are directly incorporated into the circuit function. In addition, iBias Class A even reduces the bias when the signal is at very low levels, making its operation undetectable by ear and even by standard amplifier measurements. 
In others typical sliding bias schemes, the circuit merely estimates how much bias is needed based on the input signal and an "assumed speaker load." Compared with iBias Class A, these sliding bias technologies are much less effective - and much less accurate.

XD UPDATE
Development of their "XD' circuit, is now incorporated in all new power amplifiers leaving the factory, according to David Goodman of Krell, “The XD' update to the Chorus/ Duo/Solo amplifiers reduces the output impedance to less than half of its original value. This lower output impedance better damps unwanted speaker vibrational modes. Changing the output impedance also necessitated re-compensating each amplifier stage to achieve optimal critically damped transient response. This ensures that the amplifier accurately follows the dynamics of the input signal."

BETTER SOUND 
Building on the unique Active Cascode Topology foundation of the NEW Rrange of amplifiers feature more precisely balanced current sharing among the seven sets of Active Cascode Quartets that make up the output stage. This greater precision elevates an already impressive performance envelope and provides greater amplifier reliability. Audible at all volume levels, this improvement is independent of load current. Although negative feedback in the Evolution amplifiers was already extremely low, a mere 14 dB---several orders of magnitude lower than other manufacturers' power amplifiers, modifications to the feedback circuitry allow for more ideal operation completely independent of the signal level. The results are greatly enhanced inner detail and micro-dynamics with smoother high frequency response. 
             LESS HEAT, LOWER ENERGY CONSUMPTION with KRELL'S unique iBias technology

For nearly three decades, Krell has earned a distinguished reputation for engineering innovation and product excellence. The company's history is replete with product introductions that have deeply impacted the high-end audio industry. The most discriminating audiophiles and product reviewers have consistently recognized Krell components for standard-setting performance. The sheer breadth of Krell amplifiers' dynamic range capabilities conveys a startling realism that transcends previous designs. Seemingly unlimited frequency response, combined with unerring accuracy and fortitude, extend a tradition that began with the first Krell amplifier; the KSA-100. The KSA-100 was the first high power, high-current, true Class A biased stereo power amplifier available to audiophiles. It was the first Krell product, and its resounding success established Krell as an important new technological contributor to high-end audio.

Krell newly revised Class-A iBias Technology

Krell's history is rich with breakthrough Class A amplifiers that have helped build the Krell legacy of offering the best sounding amplifiers available. Audiophiles have always considered Class A technology to be the best sounding operating state for amplifiers. However, despite Class A's unrivalled sound quality, it has fallen out of fashion because of recent demands to reduce power consumption and heat in home electronics products. Krell engineering took this challenge and redefined the meaning of high performance power amplifier. Our goal - unmatched performance, elegant design, and a compelling array of features. The breakthrough - a patent pending circuit delivering Class A operation without the excessive heat and wasted energy of conventional designs, housed in a striking new form factor, with network connectivity for advanced access and monitoring. The sound is open and unconstrained, in a manner that rivals live performance and the true sound of voices and instruments. Music and dialogue are reproduced with a richness, detail, and startling dynamics that fill a room.

Plainly stated, Class A designs are the most musically accurate circuit topology available. Class A amplifiers do not suffer from the inherent distortions that all Class AB amplifiers experience. In a traditional Class A design, the output transistors conduct full current at all times regardless of the actual demand from the speakers. Often, only a fraction of this power is needed to reproduce an audio signal at normal listening levels. The rest of the power is dissipated through the amplifier’s heat sinks, producing large amounts of wasted heat. With Krell's iBias™ technology, bias is dynamically adjusted, so the output transistors receive exactly as much power - but only as much power - as they need.

Krell's iBias Class A technology allows our latest amplifiers to run in full Class A mode to full power while minimising heat generation. Previous efforts at using a "tracking" bias, while effective, only measured the incoming signal and set bias levels from this information. Our new patent pending iBias technology significantly elevates the effectiveness of previous designs by calculating bias from the output stage. This seemingly small change in topology results in a dramatic improvement in sound quality, especially midrange richness and purity.

The core of the technology is an innovative, patent pending design for a dynamic intelligent bias circuit. Our iBias Class A circuit directly measures the output current of the amplifier and adjusts the bias to the optimum level. Because iBias Class A measures the output current, the real time demands of the specific speaker connected to the amp are directly incorporated into the circuit function. In addition, iBias Class A even reduces the bias when the signal is at very low levels, making its operation undetectable by ear and even by standard amplifier measurements.

In sliding bias schemes, the circuit merely estimates how much bias is needed based on the input signal and an "assumed speaker load." Compared with iBias Class A, these sliding bias technologies are much less effective - and much less accurate.

Power Supply Highlights

Power supply technology has always been an important contributor to the Krell sound. The power supplies of our Krell iBias Class A amplifiers have been optimised for use with the iBias circuit. Depending on the model, up to four toroidal transformers feed amplifier modules that include the audio circuitry, rectifier, and power supply filtering mounted to an individual heat sink. This design shortens the electrical path from the power supply to the output transistors, reducing the overall impedance and allowing the circuit to respond faster and control the speakers even better and more accurately.

Unlike traditional Class A amplifiers, iBias Class A amps have a compact design that allows rack-mounting, making them ideal for custom installation as well as traditional audiophile systems. This convenient form factor is made possible through thermostatically controlled ventilation fans. The fans used are specifically chosen for quiet operation, and operate at the speed required to maintain the ideal internal temperature. They run only during periods of peak energy demand - when the music is at its loudest - so they are inaudible in normal use.

Network Connectivity

The new amplifiers include RJ 45 Ethernet connectivity and an internal web page that is accessible from any smartphone, tablet, or laptop. Network connectivity brings convenience, monitoring, and reporting to end users. Amplifier configuration options include display brightness and timeout. For energy conservation, the amplifiers can be programmed to power off at a preset time of inactivity. Individual channels can be muted and firmware updates can be initiated from the web server.

Once the amplifier is connected to a network router with Internet access, the amplifier's advanced protection systems are now viewable on an Internet-connected device. Excessive current, output DC, fan speeds, short circuit, and overheating are all monitored in real time. If an issue occurs, the fault is displayed on the front panel and reported on the web server interface. Emails will automatically be sent to as many as three email addresses to notify the end user and/or the dealer of the condition.

Circuitry Highlights

The new iBias circuitry is built on a foundation of core Krell circuit technologies. All signal gain is realized in the current domain using proprietary multiple-output current mirrors with extraordinary open loop linearity. Each amplifier channel uses all discrete components. There are no generic integrated circuits or op amps used anywhere. Gain is distributed among several stages, allowing each to have a large linear operating area.

Audio signal voltages are converted to current at the amplifier input, and the audio signal remains in the current domain throughout the entire amplifier.

Current mirrors in the final gain stages use a new output power device that operates at a 73% higher voltage, delivers almost 10% more current, and offers 120 watts of additional power handling capability as compared to other devices.

With this combination, the iBias amplifiers may now deliver substantially more power while using a smaller footprint. Normally used in demanding, high-bandwidth video circuits, these transistors allow the design of gain stages with superb accuracy and very low distortion. The signal path is fully complementary and fully balanced from input to output. Independent complementary pre driver and driver stages for the positive and negative output transistors make the output stages extremely fast and linear. This unique circuit is impervious to low-impedance or reactive loads; it simply drives any loudspeaker with absolute confidence, achieving the very best possible sonic results.

Most amplifiers use coupling capacitors in the signal path to block DC and prevent damaging offset voltages from reaching your speakers. Krell amplifiers are fully direct-coupled, with no capacitors in the audio signal path. This design gives the Krell amplifiers lower internal impedance, which allows firmer, more precise control of your speakers. It also provides flatter, more extended low-frequency response, because coupling capacitors not only block DC but also affect the lowest bass frequencies. Krell employs expensive, non intrusive DC servos that remove DC without impacting the musical signal. Thus, the iBias Class A amplifiers deliver the full breadth of the music with detail, impact, and space intact.

Everything Audiophiles and Home Theatre Fans Could Want in an Amplifier

Krell iBias Class A amplifiers are the first to deliver the rich musicality of Class A amplifiers, the uncompromised dynamics of classic Krell amplifiers, and the efficiency and low power consumption of Class G and H amplifiers.

Because the iBias circuit eliminates crossover distortion, the amplifier is able to resolve more of the detail and micro-dynamics in even the best analog recordings. Simply put, the music breathes. Whether an iBias amplifier is called on to reproduce the extreme dynamic range of high-resolution digital files, the minute intricacies of a 45-rpm, 180-gram vinyl record, or the complexity of today’s latest blockbuster action film, it does so without altering or abating the music in any way.

The iBias amplifiers' unprecedented ability to retrieve the subtlest details gives their sound an incredible dimensionality, with an ambient, broad and extraordinarily deep soundstage. As spacious as the sound is, though, the amplifiers are still able to produce pinpoint stereo imaging if the recording calls for it.

It's all the power and control for which Krell has always been famous, with a level of resolution and musicality in the midrange and treble that has simply never been heard before.

In short, the new patent pending iBias Class A Krell amplifiers give today's audiophiles and home theater fans everything they could possibly want in an amplifier.

Krell amplifiers are best known for their ability to drive any loudspeaker to sound its best, without regard to impedance, efficiency, or driver style. It is linearity, an amplifier's ability to output an exact duplicate of the input signal, which is the ultimate measure of that amplifiers worth. Krell designs toward the common goal of linearity; through the rigorous application of Krell design principles that focus our efforts on four major performance factors: distortion, bandwidth, output impedance and current capability. They excell in each of these areas, delivering supreme accuracy from whisper level to astounding, awe inspiring amounts of power with grace and elegance. -A with unique iBias technology.

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DACs

KL 01 DC VAN
NZ$ 9,995.00 ea (incl. GST)
An ESS Sabre DAC feeds a classic Krell balanced, fully discrete Class A circuit which is also used in the Krell Illusion II Preamplifier. Krell Current Mode technology is employed to assure unequaled...
Coaxial and HDMI inputs support PCM up to 24-bit/192kHz. Optical input supports up to 24-bit/96kHz...
(NOTE - A GERMAN to ENGLISH TRANSLATION via GOOGLE)
DACs

Integrated amplifiers

KL 03 IA K300C
NZ$ 15,995.01 ea (incl. GST)
Renowned American amp brand, Krell Industries, has just unleashed the K-300i Integrated Amplifier. Krell made an impact with their KAV-300i integrated amplifier in 1999. Today, they are...
When it comes to high-end solid-state amps, no manufacturer is more revered or influential than...
REVIEW: The first time I heard the name Krell was in the 1956 sci-fi movie Forbidden Planet...
"Yes, it is in the upper price bracket. On the other hand, when will I own a Picasso painting? K-...
Integrated amplifiers
KL 03 IA K300D
NZ$ 16,995.00 ea (incl. GST)
Renowned American amp brand, Krell Industries, has just unleashed the K-300i Integrated Amplifier .Krell made an impact with their KAV-300i integrated amplifier in 1999. Today, they are hoping that...
When it comes to high-end solid-state amps, no manufacturer is more revered or influential than...
REVIEW: The first time I heard the name Krell was in the 1956 sci-fi movie Forbidden Planet...
"Yes, it is in the upper price bracket. On the other hand, when will I own a Picasso painting? K-...
Integrated amplifiers

Preamplifiers & Line-stages

KL 05 PA ILL2
NZ$ 15,995.01 ea (incl. GST)
 The Illusion II is the perfect centre piece for a world class digital and analog audio system. Added to the normal selection of balanced and single- ended inputs are five digital inputs. The...
EXTENDED REVIEW: The Illusion II preamplifier and power amplifier from Krell Duo 175 - The...
KL 06 PA ILL
NZ$ 32,995.00 ea (incl. GST)
Crossover Highlights Owing to Krell’s work in the Modulari Duo Reference loudspeaker, the unique crossover feature is a highly sophisticated option. When the optional board is present, additional...

Power amplifiers (Stereo & Mono)

KL 10 AS D125
NZ$ 12,995.00 ea (incl. GST)
Plainly stated, Class A designs are the most musically accurate circuit topology available. Class A amplifiers do not suffer from the inherent distortions that all Class AB amplifiers experience. In...
KL 11 AS D175
NZ$ 16,995.00 ea (incl. GST)
Plainly stated, Class A designs are the most musically accurate circuit topology available. Class A amplifiers do not suffer from the inherent distortions that all Class AB amplifiers experience. In...
EXTENDED REVIEW: The Illusion II preamplifier and power amplifier from Krell Duo 175 - The...
KL 12 AS D300
NZ$ 20,995.00 ea (incl. GST)
Plainly stated,
Circuitry Highlights Krell iBias Class A technology allows our latest amplifiers to run in...
Krell’s new iBias range is claimed to be more efficient, or less power-hungry, than pure Class A....
KL 15 AM S375
NZ$ 37,995.00 pr (incl. GST)
Plainly stated, Class A designs are the most musically accurate circuit topology available. Class A amplifiers do not suffer from the inherent distortions that all Class AB amplifiers experience. In...
EXTENDED REVIEW: The Krell Solo 375 mono block demonstrates how the amplifier business has exploded...
KL 16 AM S575
NZ$ 48,995.00 pr (incl. GST)
Plainly stated, Class A designs are the most musically accurate circuit topology available. Class A amplifiers do not suffer from the inherent distortions that all Class AB amplifiers experience. In...
EXTENDED REVIEW: The Krell Solo 375 mono block demonstrates how the amplifier business has exploded...

Home Theatre amplifiers & receivers

KL 19 PR FOUND
NZ$ 16,500.00 ea (incl. GST)
The 2013 New York Audio Show, held at The New York Palace Hotel, was practically bursting with...
KL 20 AV THEATRE
NZ$ 16,531.05 ea (incl. GST)
Krell Class A iBias Technology
EXTENDED REVIEW: "Krell has had its share of ups and downs in the past few years, and not just of...
KL 22 AV T300
NZ$ 25,500.00 ea (incl. GST)
Plainly stated,  Class A designs are the most musically accurate circuit topology available. Class A amplifiers do not suffer from the inherent distortions that all Class AB amplifiers...
KL 23 AV C4200
NZ$ 16,995.00 ea (incl. GST)
Plainly stated, Class A designs are the most musically accurate circuit topology available. Class A amplifiers do not suffer from the inherent distortions that all Class AB amplifiers experience. In...
KL 23 AV C5200
NZ$ 18,995.00 ea (incl. GST)
Plainly stated, Class A designs are the most musically accurate circuit topology available. Class A amplifiers do not suffer from the inherent distortions that all Class AB amplifiers experience. In...
Do you remember what it was like sitting for your high school or college lessons? Well, get ready...
KL 24 AV C7200
NZ$ 23,995.00 ea (incl. GST)
Plainly stated,  Class A designs are the most musically accurate circuit topology available. Class A amplifiers do not suffer from the inherent distortions that all Class AB amplifiers...
Do you remember what it was like sitting for your high school or college lessons? Well, get ready...

Reviews

Krell's Foundation brings the listener closer to that ideal than any 7.1 AV processor I have heard to date."
Mark Henninger - imagic
More than anything else, the new Foundation amazed me with its fidelity, which has always been Krell's mission—to deliver the ultimate in sound quality.  The vast majority of audio equipment is ill equipped to extract the total fidelity found within these high-resolution yet ubiquitous soundtracks. Krell's Foundation brings the listener closer to that ideal than any 7.1 AV processor I have heard to date.
 
The fact it's priced at the same level as moderately expensive projectors and speakers makes Krell's AV processor a relative bargain for the sound it produces. The Foundation is a fantastic 7.1 AV processor from a company with a long record of accomplishment, producing some of the best solid-state electronics in the entire audio industry. The Foundation deserves an audition from anyone who is truly serious about home theater and considers it to be within his or her budget. 
The 2013 New York Audio Show, held at The New York Palace Hotel, was practically bursting with esoteric audio products; many rooms contained systems priced in the 6-figure range. The overwhelming majority of the show was about 2-channel audio, but Krell was there with the new Foundation AV processor, a moderately priced (by Krell standards) 7.1 surround-sound preamp/processor with a number of features that help differentiate it from rather stiff competition.
 
One of the more impressive aspects of the Krell HT demo system was the relatively mainstream components used to highlight the new processor's prowess. This system was not a "price no object" Krell showcase—it was more of a "high price is justified by superior engineering" system—yet engineering without compromise is the precise heritage it comes from. After a long talk with Krell President Bill McKiegan, I came away convinced that the new Foundation completely justifies its price tag.
 
I had the room essentially to myself, and I chose a seat in the second row, perhaps 11-12 feet back from the front stage, just in front of the side surrounds and perhaps 8-10 feet from the rear surrounds. I chose the helicopter attack on the ranch from Skyfall to serve as a reference scene, because I am very familiar with it.
 
What I heard was quite stunning—a rear soundstage that had the same depth and definition I am used to hearing from the front. I know that is the multichannel ideal, but up until that point it had not occurred to me that the soundfield could truly be seamless and three-dimensional around the full circumference of the system.
 
I asked McKiegan about the impressive performance of the Foundation, which resulted in a brief lesson about Krell's priorities—specifically, to treat each pair of adjacent channels as an engineering challenge, optimizing those preamps to match each other so they form a perfect envelope around the listener. When the balance between the channels approaches perfection, the audio illusion is seamless. Each "channel pair" in the system becomes its own discrete, high-end 2-channel system, with the same 2-channel qualities that audiophiles are always looking for—the sonic image from two speakers takes on a three-dimensional character, with each sound discretely rendered in its proper position.
 
Since a 7.1 surround system has seven channel pairs, there are seven stereo soundfields that ideally surround the listener seamlessly. That is exactly what I heard from the Foundation—a rendition of a key scene in Skyfall that was well beyond the capabilities of my Pioneer Elite SC-55 and 7.1 speaker system, which I used to re-watch the same scene later that day. The proof? Krell's Foundation-based system immediately triggered involuntary goosebumps—something that only happens to me when I listen to the very best high-fidelity systems.
 
I asked why someone would choose Krell for a surround preamp/processor in a world where there are many choices at every level of price and quality. The result was a lengthy discussion about the company's history, the state of 4K and HDMI, and why a Vizio E701i was used in the presentation.
 
Then there's the issue of room correction. Instead of using something like Audyssey or Trinnov, Krell designed its own algorithms from scratch for the Foundation. Why? As a rule, the company designs and engineers everything in-house, to its own extremely high standards. In this case, the result is called ARES—Automatic Room Equalization System. Here is what the company has to say about it:
Quote:
"ARES analyzes all the speakers in the system, their location, phase, and distance from each other, to determine the best crossover frequency, delay, and more. In addition, ARES incorporates the acoustics of the room to determine unique EQ curves for each of the 7.1 output channels. Unlike other room EQs, ARES can be programmed to only adjust the troublesome low frequencies, leaving high frequencies unaltered."
 
The Foundation is a decidedly premium product with a price to match: $6500. That is not quite unobtainium to a serious home-theater enthusiast, but at that price point, there is concern about the risk of becoming obsolete, especially since audio and video standards keep evolving. I asked McKiegan how Krell would deal with future changes in video technology, and I liked his answers.
 
I mentioned that the home-theater market is poised on the edge of a revolution in resolution. 4K is on the way, and HDMI standards will need to be updated to accommodate 4K at higher frame rates than 30p. What happens when that day comes? McKiegan assured me that Krell could upgrade the video components, prompting a discussion of the company's long history of updating and upgrading gear as technology progresses. Faced with evolving standards, buyers of the Foundation will likely have the option of upgrading the existing unit or trading it in toward a newer model that includes the updated components.
 
So what else sets the Foundation apart? First and foremost is an all-balanced output stage—7.1 channels of it, with two summed subwoofer outputs. Another very nice feature: All ten HDMI inputs are concurrently active, so switching between them is instantaneous. Two-channel audio aficionados can also take advantage of a stereo preamp mode, featuring a dedicated all-analog signal path. 
 
More than anything else, the new Foundation amazed me with its fidelity, which has always been Krell's mission—to deliver the ultimate in sound quality. In my conversation with McKiegan, he touched on the past and future of high-definition audio. SACD and DVD-Audio are simply not mainstream products, but Blu-ray discs with uncompressed high-resolution audio sell in every Wal-mart, Target and Best Buy across the nation. The vast majority of audio equipment is ill equipped to extract the total fidelity found within these high-resolution yet ubiquitous soundtracks. Krell's Foundation brings the listener closer to that ideal than any 7.1 AV processor I have heard to date.
 
The fact it's priced at the same level as moderately expensive projectors and speakers makes Krell's AV processor a relative bargain for the sound it produces. The Foundation is a fantastic 7.1 AV processor from a company with a long record of accomplishment, producing some of the best solid-state electronics in the entire audio industry. The Foundation deserves an audition from anyone who is truly serious about home theater and considers it to be within his or her budget. 
KRELL DUO 300 - Winner of Hi-Fi News Editor’s choice award
Ken Kessler

The Krell showed blissful attack with authentic decay, and just the right amount of dryness with the percussion that opens ‘Up On Cripple Creek’. It picked up the snap of the percussion, the kick-drum air movement, with true ‘feel’. Yeah, this is a Krell, alright.

Salvation came from Lou Rawls’ At Last [Blue Note], a bit of recording perfection. It was suitably silky, Rawls’ vocals were languorous perfection, while Dianne Reeves sang as clear as a wine glass from Zalto.

Krell’s new iBias range is claimed to be more efficient, or less power-hungry, than pure Class A. Paul Miller suggests that iBias is a modern take on the popular sliding bias circuits of the 1980s. So what is the motivation for it?

Statements from the company suggest that Krell is doing its part to modernise the high-end, to increase its appeal to audiophiles who are not comfortable with bulky intrusions into their living spaces in a manner acceptable in the past. And yet nothing differentiates the Duo 300, physically, from hundreds of other ball-buster amps.

It’s a big, metal-cased block, with the usual back panel fittings. Yes, the styling is tasteful – but there’s only so much you can do with an amplifier’s looks. This is a Krell by any name and any measure. Which is as it should be.

What does differentiate the Duo 300 and its siblings from the mainstream – though other companies are fitting web links, too – is the Ethernet connection, so each amplifier can be accessed on its own web page through any device that can run a browser, eg, an iPad.

The user can then view heatsink temperature, fan speed and other information. This will also provide alerts for conditions like overheating, fan failure and shorting of the output terminals.

Blissful attack

Finding something suitable to play through the Krell for the crucial, initial impression, we chose vinyl in the form of The Band’s eponymous second LP on MoFi. In part, it’s because of the astonishing bass and that incredible drum sound, but primarily because we love the album, period!

The Krell showed blissful attack with authentic decay, and just the right amount of dryness with the percussion that opens ‘Up On Cripple Creek’. It picked up the snap of the percussion, the kick-drum air movement, with true ‘feel’. Yeah, this is a Krell, alright.

Lou Rawls’ At Last [Blue Note], a bit of recording perfection. It was suitably silky, Rawls’ vocals were languorous perfection, while Dianne Reeves sang as clear as a wine glass from Zalto.

If we seem to lack just a little in enthusiasm here, it’s only because the last Krell product we reviewed blew us away: the astonishing S550i integrated (so it should at 500w! - model since discontinued) 

The Duo 300 is certainly a good amp, but our exposure to assorted Constellation masterpieces and six months with a D’Agostino Momentum Stereo – all much more expensive than a Duo 300 (at 3 to 5times the price!) – have altered expectations of modern solid-state amplification, regardless of the Class of operation, price, or any other respects.

Consider, though, that the Duo 300 is an easy product to live with in many ways, not least the cool running and easy set-up. Moreover, there is a bonus for those who harbour insecurities about massive high-end power amps, thanks to its on-line nanny.

Verdict

Assuredly solid-state in its demeanour, Krell’s Duo 300 doesn’t, for a moment, suggest the (sonic) warmth of a true Class A amplifier likes its ancestors … which may be music to the ears of those who can’t abide ‘valveness’.  this one is for rockers.

.....Ken kessler

If you’re in the market for a new amp and are a member of the cost-is-little-object crowd, definitely check out the Chorus amps from Krell. You won’t be disappointed.
David Vaughn
AT A GLANCE 
Plus 
A new take on amplifier classes with iBias
Superb dynamics and soundstage
Ethernet capability for system monitoring 
Minus 
LED illumination too bright 
Heavy (thats part of the reason why it works so well)
 
THE VERDICT 
Krell’s iBias technology has allowed them to deliver the benefits of a Class A multichannel amplifier in a way that will have audiophiles grinning from ear to ear.
Do you remember what it was like sitting for your high school or college lessons? Well, get ready for a trip down memory lane, because to give the Krell Chorus 7200 (Chorus 4200 & 5200 are similar) the praise it’s due and explain just how much this “little”-amplifier-that-could is going to change the audio industry, we’ll need to start with a short class in “classes.”

There are many different established amplifier topologies out there, designated by class, as in Class A, B, A/B, D, G, and H. Each has its own set of plusses and minuses, but in the audiophile world, Class A has always been king for a variety of reasons. First and foremost is sound quality, which is virtually unmatched to those with golden ears—those things attached to the sides of your head, not the speaker company that Darryl Wilkinson always raves about. Audio signals are basically alternating current—the sine waves you learned about in grade school—with both a negative and positive voltage. Remember, the goal is to make a loudspeaker diaphragm move out (positive voltage) as well as in (negative voltage). The Class A amplifier has the ability to conduct the full audio signal, both the positive and negative portions of the cycle, on each output device, reducing distortion in the process.

Unfortunately, there’s no such thing as a free lunch. There’s one negative—and it’s huge: Class A’s efficiency is about as green conscious as a Lear jet carrying one passenger across the country. A pure Class A design has the output transistors operating at full power all the time; they’re never idle. This means any energy not required to drive the speaker is released through the amplifier’s heatsinks, turning the amp into a power-wasting space heater. Furthermore, the ability to place multiple channels in the same chassis is all but impossible due to the heat buildup, which has essentially shut out the technology for the majority of home theater installations.

What Exactly Is iBias? 
Krell’s audio legacy is built upon Class A amplification, and it’s no surprise that their engineers have been able to develop a patent-pending circuit delivering traditional Class A–like operation without the excessive heat and wasted energy of conventional Class A. Furthermore, the design can be housed in a form factor fit for home theater applications. It’s called iBias, but a better name may be iReallyLikeIt!

Krell’s innovative iBias technology allows the amplifiers to run in full Class A mode as needed, while at the same time minimizing heat generation. Krell isn’t the first to attempt using a “tracking” or “sliding” bias that reacts based on the nature of the audio signal, but their approach is quite different. In the past, the tracking monitored the incoming signal and set the bias based upon this information. The iBias technology takes a different approach by calculating the bias from the output stage; it directly measures the output current of the amplifier and adjusts the bias to the optimum level. Because iBias measures the output current, the real-time demands of the specific speaker connected to the amp are directly incorporated into the circuit function. The amplifier monitors the load, accounting for the variables present at any given moment, rather than blindly reacting to the incoming audio.

The president of Krell Industries, Bill McKiegan, likes to compare this technology to a 12-cylinder automotive engine, which shuts down some of the cylinders when you don’t need a lot of power. But when you slam the accelerator to the floor, the engine can deliver 600 horsepower—or more—almost instantly. iBias works virtually the same way. It can be cruising along in efficiency mode yet in a matter of microseconds give you hundreds of watts of full Class A amplification for musical peaks or when the action kicks up in the latest Hollywood blockbuster.

With this new topology comes other benefits. Krell has been able to fit seven channels of amplification into a relatively small—though extremely heavy—rack-mountable chassis, making iBias practical for use in environments where a traditional Class A amplifier would be too large. That’s not to say the Chorus doesn’t generate heat; it certainly does. Krell cools the amplifier using thermostatically controlled fans, which are generally eschewed by audiophiles and home theater aficionados. Still, in all of my testing, I was never able to detect any audible noise from the four fans on the rear of the amp, and the output temperature measured with an IR thermometer never exceeded 115 degrees F, even under the most strenuous tests.

Oh, My Aching Back 
I was out of town when UPS delivered the amp, and the arduous task of bringing the 100-pound beast (110 including packing materials) fell to my 16-year-old son and one of his friends. It took two strapping teenagers to get this baby into the house, and while it’s not the heaviest amp I’ve reviewed, it certainly is one of the most dense, and getting it into the rack was a serious chore.

Aesthetically, the Chorus 7200 is quite beautiful, as far as black boxes go. The front façade is matte black highlighted by a silver band running vertically through the center of the facing, where a backlit Krell logo protrudes slightly from the box. The left side features a small circular power button, while the right has a rectangular LCD that gives you the amp’s IP address when it powers up.

Yes, I said IP address. You see, the rear of the amp has all the connections you typically see on an amplifier: both balanced and unbalanced inputs for all seven channels, the aforementioned fans, a 12-volt trigger input, a detachable power cord, a master power button, and, unusually, an Ethernet port.

Why put Ethernet in an amplifier? In this case, the amplifier can be accessed through any device that can run a Web browser, such as a smartphone, tablet, or computer. Using the interface, you or your dealer can monitor the heatsink temperature and fan speed, as well as configure the unit to send out e-mail notifications (up to three addresses) if its onboard diagnostics detect any faults. Furthermore, if there’s ever a software upgrade for the amplifier, you can have the amp update its software from the Krell servers with the push of a button.

The Fun Begins 

Once I installed the seven-channel Chorus 7200, I hooked it up to my Marantz AV8801 surround processor and calibrated the sound levels to my speakers: three M&K S150s across the front, four M&K SS150 surround speakers, and two subwoofers—a brand-new HSU VTF-15H MK2 situated at about the midpoint of my right wall and an SVS PC-Ultra sitting in the front left corner of the room.

I lived with the Krell for a few days before really putting it to the test, but I was impressed by its neutral tonal quality out of the gate. Not too bright, not too laid-back. When I finally sat down for some critical listening, I truly started to appreciate how sweet this amp sounded.

I began with an eclectic collection of SACDs, including the Telarc SACD Sampler 1 recording of “Moanin’ ” by Monty Alexander from his Monty Meets Sly and Robbie album. This jazz-meets-Jamaica recording features Alexander gracefully moving his fingers across the keys of a Yamaha grand piano while a smooth rhythm section plays in the background, with Sly Dunbar on drums (and riddim) and Robbie Shakespeare on bass. The song is a lot of fun, with Monty’s piano slightly left of center, Sly’s drums to the right, and Robbie’s tight bass filling the room. Every strike of the piano is clean, and the midrange is full of body. As I pushed the volume higher and higher, the instrumental track never strained the amplifier, and it was able to resolve all of the detail in the music without any obvious coloration.

I could say the same for a number of Red Book CDs ripped to FLAC files on my home server. The Spin Doctors’ “Two Princes” is lyrically challenged for sure, but I’ve always enjoyed the rhythm of the track, especially the percussion beat that opens the song and the guitar solo midway through that instantly transports me back to my early 20s. Wow was the first thought in my mind as the drums kicked to life. Was the band playing live in my room? My reference Parasound Halo A 51 amp is a Class A/B that operates in Class A mode up to a few watts, but I can’t say that I remember this recording sounding quite this crisp and clean, with the voices projecting well into the room and the guitars layered in the background.

Class A amp makers tout their products’ ability to re-create voice, and here the Krell truly shined. Take the start of fun.’s “Some Nights,” where Nate Ruess’ voice kicks off the song with a catchy ballad-like opening that transports you back in rock history to harmonies from groups such as Queen and Styx (those bands also shine on the 7200). With this amp in the chain, Ruess’ melody came alive with seemingly limitless dynamics, a 3D-like soundstage, and amazing detail.

This dynamic performance was readily apparent with every Blu-ray I threw at the Krell. The beach landing in Saving Private Ryan exploded into my room, with each discrete effect placed precisely in the soundstage. And the 7200 brought an uncanny immediacy to softer passages, such as the opening monologue recited by Morgan Freeman in Clint Eastwood’s Million Dollar Baby, where it truly sounded as if Freeman was sitting in the room with me describing Frankie Dunn’s personality and why he wouldn’t train girls to fight. Impressive is an understatement.

A Strong Foundation 

I spent the vast majority of my review time using my reference Marantz surround processor, but Krell really wanted me to pair this fantastic amplifier with their entry-level Foundation surround processor ($6,500, an S&V Top Pick of the Year, reviewed April 2014). Michael Fremer raved about the Foundation’s prowess in his review, and I have to concur 100 percent. As good as the Chorus 7200 sounded with my Marantz, the Foundation took it up a notch, and I now have some serious processor envy and a strong case of upgrade-itis due to this combo’s audio muscle. The Foundation isn’t the most ergonomically friendly processor I’ve ever used—setting it up was about as much fun as a root canal—but it’s by far the best-sounding. The soundstage is incredibly convincing: You can’t really tell where the speakers are in the room, and the subwoofer integration is by far the best I’ve ever experienced. Like Michael, when I put my Marantz back in my rack, I felt like I needed a prescription for Prozac to fight the depression I was facing.

Putting It Into Words 

The hardest part of reviewing audio equipment is putting what you hear into words that can impart upon the reader just how impressive (or uninspired) a particular piece of equipment was to your ears. In the case of the Chorus 7200—and Foundation—it was six weeks of audio bliss for me and my family. My son actually sat on the couch with me to listen to music because it had never sounded so alive, but when I broke the news that the processor/amp combo cost $16,000, he knew instantly our days of audio bliss were numbered.

The only complaint I have about both the amp and processor is the non-dimming backlight that hides behind the Krell logo on each unit. When I was listening to music, they didn’t bother me one bit, but when the room lights were off and I was trying to watch a movie, the blue LEDs were so bright that I thought they might be able to lead a wayward ship into port after a long journey at sea.

The Chorus 7200 isn’t cheap by any means, but its iBias technology delivers bliss for a relatively low cost per channel when compared against the cost of traditional high-end Class A amps. If you’re in the market for a new amp and are a member of the cost-is-little-object crowd, definitely check out the Chorus 7200 from Krell. You won’t be disappointed.

I've never encountered another amp that combines the Solo's 375 warm, wonderful, involving sound with such a practical and versatile design.
Brent Butterworth

REVIEW SUMMARY: Spending this sort of money on a pair of mono-block amps is a lot, but the Solo 375 delivers a lot. It combines a very smooth, un-solid-state, un-hifi sound with loads of power and dynamics, plus a design that works great whether you're plopping the amps on the floor by the speakers or shoving them out of sight into a closet or equipment cabinet. In fact, I'd go so far as to say I've never encountered another amp that combines the Solo's 375 warm, wonderful, involving sound with such a practical and versatile design.

EXTENDED REVIEW: The Krell Solo 375 mono block demonstrates how the amplifier business has exploded with classes, so many classes that even people in the audio industry often get them confused. Twenty years ago, almost everything was Class AB or Class A. Now it's also common to see Classes D, G, and H. We also see "made up" classes--marketing terms rather than official designations--such as Class I, Class T, and Class AAA. We can find most of the above classes executed with compact, efficient switching power supplies or with traditional analog supplies using transformers and big storage capacitors.

What's the best? That depends on how you define "best," but audiophiles generally believe Class A delivers the best sound quality. With Class A, the amp's output transistors or tubes never switch fully off, so there's no crossover distortion--that ugly, high-frequency artifact caused when an amp's positive-polarity transistors or tubes hand off the signal to the negative-polarity transistors or tubes.

Why isn't everything Class A, then? Because Class A wastes a lot of power. It dissipates the entire output of the amp's power supply either as sound through the speakers or as heat through the amp's heat sink...but mostly as heat, which makes it impractical to use Class A amps in places where heat can build up, such as in equipment cabinets or closets.

Krell's Solo 375 and the other amps in the company's new iBias Series adapt Class A to a world in which electronics power consumption is an increasing concern and the desire to hide the electronics is a top priority for many customers. The iBias technology uses a Class A output stage in which the bias--the ever-present voltage that keeps the transistors turned on all the time--is continuously adjusted so there's only as much as needed for the signal the amp is playing at that moment. Thus, there's not that huge amount of excess power that must be dissipated as heat. Power consumption is lower, less heat sinking is needed, and the amp can be made smaller. Assuming the circuit that controls the bias works as intended, the iBias amps should give you all the sound quality of Class A with none of the drawbacks.

If this technology sounds vaguely familiar, it should. It's similar in ways to Classes G and H, which use a "tracking" power supply that reduces voltage at lower signal levels but typically employ a Class AB output stage. A few years ago, Sony introduced a high-end Class A amp with a tracking power supply.

However, Krell's iBias approach is different. Rather than using the input signal to adjust the bias or the power-supply voltage, iBias tracks the output current. The advantage of this approach is that iBias can optimize the amp's performance for your specific speakers, rather than for an assumed speaker load. Even though iBias should result in more accurate optimization of the amp's operation--cutting the bias "closer to the edge," if you will--my assumption is that Krell chose to supply a comfortable margin of bias voltage to the transistors. Why do I guess that? Because despite the Solo 375's large chassis, it has cooling fans: two thermostatically controlled, low-RPM fans that are managed so that their sound should be inaudible. Clearly there's some wasted heat being generated.

Krell-375-mono.jpgNot only is the Solo 375's amplification technology innovative, but its control system is, too. If the amp is wired to an Ethernet network through the RJ-45 jack on the back, you can access a web page for each amp. The web page shows current operating temperature, fan speed, overload conditions, etc.

The Solo 375 is rated at 375 watts into eight ohms and 600 watts into four ohms. The iBias line also includes the 575-watt Solo 575 mono block, as well as two-, three-, five-, and seven-channel models. All use a similar chassis design, and all can be rack-mounted.

All of the amps in the line use fully balanced, fully complementary circuits through the entire audio path. In essence, each circuit comprises two "mirrored" halves, one of which operates on the positive half of the audio signal and the other on the negative half. This is the way most of the bigger, more expensive high-end solid-state amps are made; it reduces noise and improves the slew rate (the speed at which the amp can go from zero volts to full output).

The Hookup

The moment I unpacked the first of the pair of Solo 375s I received for review, it immediately became my favorite Krell ever. Or at least, my back's favorite Krell ever. Despite its bulk, it weighs just 60 pounds.

For some audiophiles, this will be a problem. Krell has built its history on amps with back-breaking weight, and some Krell enthusiasts cherish the fact that their amps require two strong people to lift. When a visiting headphone manufacturer saw the two Solo 375s on my floor, awaiting setup, he picked one of them up, and an immediate look of shock crossed his face. "That's a KRELL?" he blurted. I explained the whole iBias technology and pointed out the fans, but he just rolled his eyes. I've seen at least one other audio reviewer express similar sentiment.

I put the Solo 375s on thick MDF platforms to elevate them above my carpet. I connected them to two different pairs of speakers: my usual Revel Performa3 F206 towers and my cherished Krell Resolution 1 towers. I don't often use the Resolution 1s because they weigh 200 pounds each and are thus impractical to move in and out of my system often, but I thought the occasion merited the effort.

The Solo 375s got their signals primarily from a Krell Illusion II digital preamp, using either a laptop computer or a Music Hall Ikura turntable (with an NAD PP-3 phono preamp) as the source--mostly the former, using my own ripped WAV files or tunes streamed from Tidal. I used balanced professional Canare Star Quad XLR cables to connect the preamp to the amp and AudioQuest CinemaQuest 14/2 speaker cables.

The whole time I used the Solo 375, including some crank-it-up rock listening sessions and a couple of action movies, I only ever heard the fans when my ears got within a couple feet of the amp.

Performance

I've never been a Diana Krall fan, but it's hard not to be captivated by Wallflower, her new album of covers of classic rock tunes. In just the first 20 or 30 bars of her take on Elton John's "Sorry Seems to Be the Hardest Word," I learned a lot about the Solo 375. I was struck by how intimate and warm Krall's voice sounded. She sounded like she was right in the room with me, about eight feet away, with very little ambience. In fact, based on her voice, I'd almost have thought someone deadened up my listening room with about 30 square feet of Sonex foam. But the instruments sounded huge and spacious, much as in Elton John's original recording. The spaciousness didn't sound like the result of exaggerated treble or phasiness, and it rarely produced a "wow" reaction from me; it merely sounded natural. In terms of sheer involvement, this was a higher level than what I'm used to hearing from my Revels.

You're probably sick of hearing the Mark Ronson/Bruno Mars tune "Uptown Funk," but it happened to come up on the home page of the Tidal app, so I played it just out of curiosity. It'd be easy to dismiss this as insubstantial pop fluff; but, through the Solo 375 and the Resolution 1 speakers, I could hear that it's actually a musical and sophisticated production. The Solo 375's sound suited Bruno Mars' voice, which is smooth but not deep and thus might sound grating through some amps. Through the Solo 375, it sounded positively liquid, yet there was nothing soft about the bottom end; the Solo 375 kept each Resolution 1's dual woofers in perfect control, producing tight, deep, powerful bass tones. Again, the unexaggerated, natural-sounding spaciousness pulled me in. 

Based on these and some cuts I'd heard before, I was starting to wonder if the Solo 375/Resolution 1 combo could conjure a really huge sense of space. I found out fast when, on its own, Tidal went straight into Mars' "Locked Out of Heaven." The tune's background vocals almost literally jumped out of the speakers, actually seeming to come from behind me. This is a pretty easy trick for big panel speakers like MartinLogans and Magnepans, but not many systems using conventional dynamic drivers can so convincingly wrap sound around you.

Having heard enough pop singers for a while, I shifted over to one our greatest anti-pop singers: James "Blood" Ulmer. Ulmer's Odyssey album is an idiosyncratic masterpiece, consisting only of drums, violin (often played through a wah-wah pedal), hollowbody electric guitar (with all the strings tuned to A), and Ulmer's inimitable vocal stylings. The Solo 375 got all the spacing right, the natural reverb of the space in which the drums were recorded contrasting perfectly with the much more intimate sound of the close-miked vocals and the reverb-soaked violin lines. Ulmer's vocals also sounded just right: smooth and soulful, but with that little trace of edge that makes Blood Blood. (BTW, I've seen Ulmer live more than any other artist, in widely varying venues and numerous musical settings, so I'm pretty familiar with his sound by now.)

Not surprisingly, the Solo 375 sounded great with rock, too. R.E.M.'s "Pilgrimage," from Murmur, the group's first full-length album, isn't something anyone would mistake for a Led Zeppelin or Deep Purple tune, but all the elements are there: a dynamic, insistent drum sound with a huge-sounding snare and a powerful vocal performance backed by highly reverberant background vocals. (OK, so it has chimes in unison with the guitar. That doesn't mean it's not rock.) The spaciousness that worked so well for the other recordings came through on "Pilgrimage," too, and I especially loved the power of Bill Berry's kick drum and the way his firm snaps of the snare drum came through with loads of dynamics but not a track of edge.

Basically, the Solo 375 sounded like the world's most powerful tube amp. The tonal and spatial character, combined with the warmth of the mids, reminded me of some of the big push-pull tube amps with quartets or octets of KT88 tubes. By and large, that's a good thing.

The Downside

One of the things that made the Solo 375 remind me of a tube amp is that the top end is smooth and not in any way "hifi sounding." Personally, I like that. But I know some audiophiles don't--they want to hear every last little detail in a recording, even if they need a somewhat elevated or edgy treble to get it. If that's you, that's okay. In audio, you gotta go with what makes you happy. Just know that, if what makes you happy is a lot of treble detail (apparent or actual), the Solo 375 probably isn't your amp.

Comparison and Competition

I had a chance to compare the Solo 375 with a couple of other big solid-state amps: Classé Audio's CA-2300 and Pass Labs' X350.5. The latter, incidentally, runs in Class A for the first 40 watts; so, for all intents and purposes, it's almost always running in Class A and thus makes an interesting comparison for the Solo 375. Using a one-kilohertz test tone, I matched the amps' output levels within ±0.1 dB and connected them all to the Resolution 1 speakers.

A particularly illuminating track for comparing almost any kind of audio gear is Trilok Gurtu's "Once I Wished a Tree Upside Down," a light saxophone melody backed by shakers, tabla, and synthesisers. In the intro, the shakers swirl around your listening room; the degree to which they wrap around my listening chair is one way I judge a system's soundstaging capability. With the CA-2300, the treble sounded wonderfully detailed and delicate, but the action all seemed to be taking place in front of me rather than around me. With the X350.5, I got a greater sense of spaciousness and wraparound, but the treble didn't sound as smooth as with the Classé or the Krell. The Krell got the spaciousness just right, but because its treble was smoother/softer, it didn't have quite that level of excitement that the others did. 

I listened to some more jazz and pop cuts through all three amps, but the comments were the same thing over and over. All three had ample dynamics and bass; it's mostly the character of the treble and the spaciousness of the sound that varied. Which one will you like better? That depends on your personal taste. But if smoothness and spaciousness rank high on your list of priorities, the Krell seems like the best bet to me.

Conclusion

Spending this sort of money on a pair of mono-block amps is a lot, but the Solo 375 delivers a lot. It combines a very smooth, un-solid-state, un-hifi sound with loads of power and dynamics, plus a design that works great whether you're plopping the amps on the floor by the speakers or shoving them out of sight into a closet or equipment cabinet. In fact, I'd go so far as to say I've never encountered another amp that combines the Solo's 375 warm, wonderful, involving sound with such a practical and versatile design.

Given its power output, the Solo 575 might be a relative bargain.
Michael Fremer 

SUMMARY - REVIEW OF EARLIER VERSION, SINCE REPLACED BY NEW XD VERSION: The Solo 575s' taut bottom end produced always entertaining rhythmic drive and pleasing musical flow. Their punchy but nonaggressive top end was likewise fast, and the surprisingly silky ultratop, which appeared when least expected and was always very welcome, added to the endless excitement and strong listening involvement these amps produced in me

EXTENDED REVIEW: Class-A amplifiers have a well-deserved reputation for being power guzzlers that run hot enough to burn fingers. They're inherently inefficient because their output devices conduct full current at all times, and much of that current is dissipated as heat—requiring, in the case of class-A solid-state amplifiers, massive heatsinks. This is why class-A amps tend to produce relatively low power, and tend to be heavy and expensive to buy and run. And these days, energy inefficiency is out of fashion.

These disadvantages are the results of class-A's advantages: When output devices are biased for class-A operation, the crossover distortion normally generated as the signal swings from positive to negative and back is eliminated. And that, say class-A fans, is the source of the breed's magical sound, which is often described as smooth, rich, and coherent from top to bottom.

iBias

While class-A amplifiers figure prominently in Krell Industries' genome, the company has steered clear of them for a while—presumably for the disadvantages described above, and because those disadvantages make traditional class-A amplifiers impractical for home-theater-friendly, high-powered, multichannel systems. And I would guess that Krell isn't willing or able to invest in a separate line of mono or stereo class-A amps designed only for audiophiles.

A class-A amp that would be sensible for use in a multichannel system would have to produce a prodigious amount of power, be of practical size, consume little power at idle, and run relatively cool, eliminating the need for massive heatsinks; Krell's recently developed iBias technology (patent pending) appears to fulfill those requirements. iBias is conceptually similar to the sliding-bias or tracking-bias amps of the past—Nelson Pass's Threshold 800A of the 1970s might have been the first—in which input signal was monitored, and that information was used to adjust the bias voltage, all based on an assumed speaker load. Krell's iBias circuit is said to monitor the amplifier's output current, which the company claims is a far more precise and efficient arrangement because it measures the real-time demands of the specific speaker to which the amp is connected.

Krell uses iBias in a broad range of models: monoblocks, as well as amplifiers of two, three, five, and seven channels. The subject of this review, the Solo 575 is their most powerful iBias monoblock. In fact, the Solo 575 is unusually powerful for a class-A amp, outputting a claimed 575W RMS into 8 ohms or 900W into 4 ohms, yet weighing only 70 lbs and having no external heatsinks. Instead, heat is dealt with by four small, thermostatically controlled fans on the rear panel that exhaust through the top panel.

If you're skeptical about Krell's claim that a class-A amplifier of that size and weight can output that kind of power without heatsinks, you're not alone: If its bias voltage varies with demand, can it even be called a class-A amp? And does it sound like one? Maybe John Atkinson's measurements will offer an answer to the first question. I'm better qualified to answer the second.

Description

Aesthetically, the new Krell looks more like a conventional class-A/B amplifier. Rather than being housed in a milled-aluminum case with a thick top plate, the Solo 575 is wrapped in a thin, U-shaped cover—the kind usually found on better home-theater receivers and processors: That's a money-saver, as is the absence of heavy heatsinks along the sides. But the amp does have a thick aluminum faceplate, of the same (attractive) curved design used throughout Krell's line—including the superb-sounding Foundation surround-sound processor I reviewed in March 2014 for Sound&Vision. Like the Foundation, the Solo 575 has a somewhat dated-looking LCD screen, which displays the unit's IP address—more about that later—and alerts you to fault conditions. For those of you too young to remember, in the old days, amplifiers communicated problems like shorted speaker terminals with smoke signals and, sometimes, flames.

On the Solo 575's rear panel are single-ended RCA and balanced XLR inputs, excellent and easy-to-use WBT NextGen speaker binding posts, a power switch, a 12V Trigger input, an RJ45 Ethernet connector, and the aforementioned cooling fans, as well as Krell's proprietary CAST (Current Audio Signal Transmission) Lemo connector input, for use with Krell front-end components.

From input to output, the Solo 575's circuitry is fully complementary and fully balanced, and uses all discrete components. At the input stage, the incoming signal is converted to current by proprietary multiple-output current mirrors; from there on, all gain is applied as current gain. Throughput is direct-coupled—there are no capacitors in the signal path—for lower internal impedance and, according to Krell, more precise control of the speaker, as well as flatter and more extended low-frequency response. DC servos are used to remove DC from the output.

When I asked Bill McKiegan, president of Krell Industries, about the Solo 575's price which, despite the money-saving construction, he quickly cited the considerably higher prices of earlier Krell monoblocks; I would add that competing amplifiers that output far fewer watts but are housed in more substantial cases can cost upward of US$50,000/pair I've reviewed quite a few of those in the last few years. Given its power output, the Solo 575 might be a relative bargain.

Easy Setup

After connecting it to a network router—that's where the RJ45 jack comes in—and entering the amplifier's pre-assigned IP address from a Web browser on a computer or tablet, the Solo 575 user can access that amp's individual Web page. From there, the user can monitor the Solo 575's thermal status, as well as put it in mute and download software updates. The page can alert you to fault conditions, such as crossed speaker wires. Any detected fault automatically triggers an e-mail to Krell, who then enter the unit's serial number in their database and notify the dealer who sold it to you (as well as the many audiophiles at the National Security Agency).

I spent time driving the Solo 575s' balanced XLR inputs via the transformer-coupled XLR outputs of my darTZeel NHB-18NS preamplifier, but I did most of my listening with the darTZeel's single-ended outputs driving the Krell's single-ended inputs.

Take 1

I'm not biased for or against class-A amplifiers—or, for that matter, for or against class-A/B amps, though the latter are what I've mostly owned over the years. The solid-state class-A amplifiers of my experience have always sounded velvet-smooth, non-electronic, and often tube-like, though some have sounded softer than I like. It's easy to understand the enthusiasm for class-A among many audiophiles, especially in terms of sonic purity and an absence of electronica.

I put on a recent vinyl edition of Eiji Oue conducting the Minnesota Orchestra in Copland's Symphony 3 and Fanfare for the Common Man (200gm LP, Reference RM-1511)—a recording with enormously dynamic, well-extended, texturally supple, room-rattling bass-drum thwacks. I immediately heard a muscular, well-textured bottom end as the Solo 575s exerted a superior grip on the woofers of my Wilson Audio Specialties Alexandria XLF speakers, compared to that of my reference DarTZeel NHB-458 monoblocks. The weight and power of the Krell amps were undeniable: They had a bottom-end whomp that reminded me of Bel Canto Design's $50,000 Black amplification system—and that's a compliment.

I had used the Copland LP to evaluate the Swedish Analog Technologies tonearm through my darTZeel amps, and while that bass was impressive in every way, the Solo 575s' transient slam and grip on the Wilsons' woofers took it to another level of excitement. Put it this way: The SAT arm's contribution to the sound of my system was like adding a subwoofer; with the 575s in the system, it was like adding a second sub—or even a third—so powerfully deep, throbbing, yet well controlled was the bottom end. There wasn't more bass; instead, what bass there was was just better controlled and better damped.

The overall sound was definitely drier than the darTZeels, but this was still at the very beginning of my listening. I decided to stop analyzing and instead just listen for pleasure—the way I used to before this became a job—to find out if my auditory pleasure zones would, over time, connect with the sound of my system as driven by the Krells: something that did not happen with the Bricasti Design M28 monoblocks (US$30,000/pair).

I pulled out some of the many thousands of LPs I have that have never been played. One was a still-sealed copy of Music of Lodovico Giustini, Volume I, Performed on the 1720 Cristofori Pianoforte at the Metropolitan Museum of Art by Mieczyslaw Horszowski (LP, Titanic Ti-78, footnote 1). Obscure? Yes! But here's a "harpsichord with hammers" that has no pedals and thus no pedal-actuated sustain. This perfectly quiet pressing (after an ultrasonic cleaning) of a wonderfully dry yet tactile recording, made in the museum's André Mertens Galleries for Musical Instruments, brought the performance to life in my room—and from Horszowski's perspective.

The Solo 575s and the SAT tonearm were made for that instrument's rich, powerful lower register and its paucity of sustain, which were reproduced with unflinching control and solidity. The sonic integrity seemed well maintained up and down the keyboard, and was free of electronica.

Next up were Mozart's four horn concertos, with Lowell Greer playing a valveless natural horn (made in 1987, after an 1818 original made by Raoux, in Paris), and Nicholas McGegan leading the Philharmonia Baroque Orchestra, recorded in the chapel of San Francisco's Lone Mountain College (LP, Harmonia Mundi USA HMU-7012). The recording engineer was Wilson Audio Specialties' Peter McGrath, who was then still recording in the analog domain. (He now makes digital recordings in high-resolution surround sound.) Mastering was by the late, great Doug Sax at the Mastering Lab. I didn't know either man was involved before I removed the shrink-wrap. That's part of the fun of collecting records.

Through the Krells, Greer's horn had a warm, vivid, pleasingly soft sound, its image suspended between the speakers in a soundstage of moderate depth. The other horns, woodwinds, and strings were also nicely rendered, producing an enveloping and satisfying listening experience.

I then compared an original pressing of Neil Young's On the Beach (LP, Reprise R 2180) with the reissue included in the boxed set of Young's Official Release Series Discs 5–8 (4 LPs, Reprise 535704)—initially not to test the Krells, but as part of a review of the Young set. Chris Bellman had cut the new LPs from the analog master tapes (which I saw, stacked behind the board, during a visit last year to Bernie Grundman Mastering). I focused on one of Young's most elegant melodies: "See the Sky About to Rain." It opens with a tremoloed Wurlitzer electric piano laying out the chords, followed by a pedal steel guitar in the right channel, and a thick-sounding drum kit centered behind Young's voice.

Both versions sounded better than I'd ever heard them. What I learned was that the original pressing's richer sound came at the great expense of image precision, focus, and clarity. The reissue put all of the instruments and voices in far more precise focus, though the warmth of Young's voice in the original was now somewhat harsher. The bottom end had greater punch and precision. Though I found the reissue better focused overall, especially the drums, I could make a case for either pressing and both demonstrated that the Solo 575 didn't produce the velvety transients and textures I expect from class-A. With both pressings, the cymbals sounded neither romantic nor soft. In fact, they were a bit crunchier than I'd expected.

Class-A with an *?

During the time when I stopped analyzing the Solo 575s and simply enjoyed the musical ride, I was always, with familiar recordings, well aware of the augmented bass wallop: The effect was always pleasurable, and produced exhilarating rhythm'n'pace. Otherwise, I was able to let go of the darTZeels' more familiar sound and fully accept that of the Krells—though I was also well aware that the Krells' sound was less refined overall. What I expect from class-A amplification—textural richness, suppleness, delicacy of attack, generous sustain, and far-as-the-ear-can-hear decaysnever materialized. But the far more expensive darTZeels (151,000 Swiss francs/pair, equivalent to US$157,000/pair at the time of writing) produced all of those in greater abundance.

Instead, the Solo 575s' overall attack was speedier, with less generous sustain and somewhat steeper/faster decay than through the darTZeel amps. However, those qualities better matched the Krells' punchier low-frequency personality. The Solo 575s breathed as a tightly sprung whole, producing a coherent sound from top to bottom.

I felt that, at higher SPLs, the Krells were adding a splash of hash and/or brightness, which somewhat offset the strong pluses of their tighter grip and rhythmic tautness. This was most audible with pop and rock recordings and vocals, and less so with recordings of unamplified instruments. But this characteristic wasn't to the point of being distracting or objectionable. It was audible only occasionally, and then gone. At the same time, when a recording contained very high frequencies, or a mix with a high-frequency EQ lift, those frequencies were reproduced with an unexpectedly sweet and silky quality.

The last record I played before returning to the darTZeels was an AAA reissue of Sam Rivers's Contrasts, recorded in December 1979 (LP, ECM 1162). Rivers plays soprano and tenor sax and flute, George Lewis plays a monstrous, sometimes blatty trombone, Dave Holland is on bass, and Thurman Barker plays drums and mellifluous marimba. Mention free jazz to many—even some Frank Zappa fans—and they freak out. They're hung up. Why anyone who enjoys Zappa's good-humored, nonstructured meanderings wouldn't dig Contrasts escapes me. In "Circles," Lewis blats away in the left channel, Rivers blows on soprano and Barker drums in the center, and Holland bows in the left channel. It's closely miked and pleasingly raucous. At high SPLs, the entire record produces delirious chaos.

Contrasts brought forth all of the Solo 575's strengths: punchy, woofer-gripping lows, whether from plucked or bowed bass or growling trombone; pleasingly sizzly but not overly hashy cymbal strokes; and smooth, almost silky upper highs from Rivers's flute. The sound was brash yet involving, the images large and pleasingly confrontational. 

Swapping in the darTZeel NHB-458s and playing the heavily panned drum solo in "Zip," also from Contrasts, put the differences between the two amps in sharp focus. The darTZeels produced less bottom-end grip but more nuance. Cymbals had more sizzle and less crunch, and there was more air around Rivers's flute. The soundstage was wider and deeper, and aural images on it were more compact and better focused, though edge definition was less severe. The overall sound of the far more expensive darTZeels was more refined, in terms of both transient performance and dynamic gradations.

In short, the class-A/B darTZeels simply sounded more like class-A amps than did the Krells. Listening to the Krells, I missed what the darTZeels did best; listening to the darTZeels, I missed what the Krells did best.

Playing a long set of tunes stored in the Meridian Sooloos—all from CDs ripped at full 16-bit/44.1kHz resolution—verified the positives and negatives revealed by this comparison, though they were always complementary in ways that made me want to keep both sets of monoblocks on hand, one pair each for different types of music.

For instance, in "There'll Be Some Changes Made," from Chet Atkins and Mark Knopfler's Neck and Neck (now 25 years old . . . how can that be?), via the Krells the taut bass line more effectively tapped my toes and carried forward the tune. The darTZeels' sound was more supple, expressing greater stage depth and, especially, width, and the guitars were better separated from the reverb. The same was true with the CD-resolution file of Chuck Berry's "Rock & Roll Music": the Krells exacerbated the glare of the reverb, but startlingly clarified the piano and, especially, some of the percussive accents buried by the more-than-six-times-the-price darTZeels.

Equivocating Conclusion

In the past few years, apart from my reports in "Analog Corner," I've reviewed mostly power amplifiers. Every one of them has sounded different from all the rest, and I could happily live with some, but not others. The Bricasti M28 monoblocks, for instance, which measured as well as the Krell Solo 575s, according to JA, didn't tickle my auditory pleasure centers as much, despite the Krells' somewhat coarser overall sound.

The Solo 575 monoblocks were in my system for well over a month, and during that time I enjoyed how they drove the Wilson Alexandria XLFs, especially on the bottom. But more important—because the sound was whole from top to bottom—I found no fault with any single aspect of Krells' sound until I swapped them out for the far more expensive darTZeel NHB-458s.

The Solo 575s' taut bottom end produced always entertaining rhythmic drive and pleasing musical flow. Their punchy but nonaggressive top end was likewise fast, and the surprisingly silky ultratop, which appeared when least expected and was always very welcome, added to the endless excitement and strong listening involvement these amps produced in me.

When I returned to the darTZeels, my system's sound was texturally more subtle overall, and in some ways more polite. but I also happily listened to a great deal of classical music through the Krells.

If you listen to rock, and your speakers have good bottom-end extension, and—especially—if they thrive on lots of power and can deliver wide dynamic swings, you need to hear the Solo 575s. ……. Michael Fremer

I was always very, very happy with the sound of my system when the Illusion II was in it.
Brent Butterworth | April 20, 2015

SUMMARY: Bassist Ray Brown's Soular Energy is one of those CDs that sounds at least pretty good on almost any system, but I thought the Illusion II particularly nailed "Mistreated But Undefeated Blues." The part that the Illusion II got especially right was guitarist Emily Remler's tone, which has plenty of body (like her heroes Herb Ellis and Wes Montgomery) with just a touch of twang. I thought the Illusion II got Remler's badass sound just right. 

Even the (arguably) toughest test track I have, the live stereo version of James Taylor's "Shower the People" from Live at the Beacon Theatre, sounded smooth, natural, and colourless (but in a good way) through the Illusion II. Vocalist Arnold McCuller's solo at the end--a bravura performance that taxes the midrange reproduction of audio components--never broke up or got edgy or bright.

EXTENDED REVIEW: It seems like, every few years, Krell goes through a major cosmetic (and sometimes engineering) revamp. Visually, the song always seems to be the same: variations on the unashamedly macho look that began with the KSA-100 amplifier way back in 1981. The new Illusion II digital preamp embodies the same industrial design ideas as the new iBias amplifiers: a more understated (or less overstated) look, with a form factor conducive to rack-mounting. It's still macho, though.

Engineering-wise, there's nothing particularly "revamped" about the Illusion II. It's a straightforward high-end digital preamp--i.e., an analog preamp with a built-in digital-to-analog converter, a concept that's rapidly becoming the norm in two-channel audio. The Illusion II has five digital inputs feeding its 24-bit/192-kilohertz ESS Sabre DAC: one AES/EBU, two coaxial RCA, and two Toslink optical. If it seems like something's missing, it is: there's no USB input. USB audio inputs have become ubiquitous only over the last couple of years; and, according to company president Bill McKiegan, the Illusion II was too far along in its development cycle to add USB. This isn't a big deal; you just need to add a USB-to-coax converter, which I'll discuss in the Hookup section below.

The Illusion II also has four stereo analog inputs: three RCA and one XLR. There's no built-in phono preamp; so, if you want to use a turntable, you'll have to provide the phono pre. XLR and RCA stereo outputs are provided, as is a quarter-inch front headphone jack.

For the Illusion II, Krell uses much the same control system as in its other recent preamps and integrated amps (including the S-300i integrated I usually use for speaker reviews). You can do all the normal stuff, like volume and input selection, from the front panel or remote. A front-panel alphanumeric display with a menu system lets you access more exotic features, such as balance, home theatre bypass, input trim and naming, and the function of the 12-volt DC trigger jack on the back (which can send out a trigger voltage to turn on your amps when you turn on the preamp).

Krell's website touts four main features of the analog circuitry: current mode design; a fully balanced circuit topology, in which separate circuits amplify the positive and negative halves of the audio signal; dual-mono layout, with separate circuit boards for left and right channels; and a power supply with 40,000 microfarads of storage capacitance, which is a lot for a preamp. Of course, all of this reflects well on the construction quality, but none of it really tells you how the Illusion II is going to sound.

The Hookup

Let's get past that big issue I cited above: the Illusion II's lack of a USB input. It seems to me that almost everyone who buys this stereo preamp would want to use a computer as a source device, so finding a way to connect a computer to the Illusion II is priority number one in any installation. What you need here is a USB-to-coax converter: a "dumb box" that simply converts the USB from your computer to an SPDIF coaxial RCA digital output that the Illusion II can accept. I ended up using a Peachtree Audio T1 converter--which costs $79, worked instantly with my Toshiba laptop running Windows 7, and required no driver installation. The T1 only passes resolutions up to 24/96, though; if you want 24/192, spend $149 for the Peachtree X1. Of course, other manufacturers offer higher-end options you can explore. (Unfortunately, I started with the NuForce U192S converter, which I picked up for $49, but I couldn't get it to work with my PC or a friend's Mac, even after installing the drivers downloaded from the company's site. NuForce's only product support was a phone number with an answering machine that promised a company rep would call back, but no one ever did. So I recommend that you get one of the Peachtree models instead.)

I used the Illusion II with a couple different amps: the Krell Solo 375 mono blocks and a Classé Audio CA-2300 stereo amp. Speakers were either the Revel Performa3 F206 midsized towers or the Krell Resolution 1 large towers. Interconnects were all Canare Star Quad, and speaker cables were AudioQuest CinemaQuest 14/2. Most of my listening was using my Toshiba computer as the source, but I also used my Music Hall Ikura turntable and NAD PP-3 phono preamp to get an idea of how the Illusion II's analog section sounds. I also used it in home theater bypass mode along with my Denon AVR-2809CI receiver (used as a surround processor only), with the Krell amps handling left and right channels and an AudioControl Savoy seven-channel amp handling the center and surrounds.

The only thing I didn't like about using the Illusion II is that its digital inputs are accessed differently from the analog inputs. Each analog input has its own dedicated button on the remote and the front panel, but accessing the digital inputs is much less intuitive. From the front panel, you press the Digital button to switch over to the digital inputs, then hold the button down for a second to scroll to the next input. From the remote, you press the Digital button, then scroll through the inputs using the Select button. I think an extra row of buttons that allows direct access to the digital inputs would be welcome.

All comparisons cited in the review were conducted with levels matched to within 0.1 decibel.

Performance

I listened to the Illusion II on a casual basis for about a month before I sat down for a serious evaluation, and in that month I didn't notice any particular sonic character or idiosyncrasy. In fact, my attention was never drawn to the preamp. It always worked fine and sounded great.

When I sat down to do an in-depth evaluation, I started by using the analog inputs with my turntable so that I could get an idea of the sound quality of the core analog circuitry. As best as I can describe it, the sound quality was, well, mostly nothing. I couldn't pin down any particular coloration or tonality, even though I easily heard differences among different amplifiers, audio codecs, and other audio products I tested while the Illusion II was in my system.

One thing I loved about the Illusion II's sound was that I never found it harsh, edgy, or bright. For example, on "Matte Kudasai" from the LP Levin Brothers, by bassist Tony Levin and keyboardist/arranger Pete Levin, the brushed cymbals can sound a bit edgy and steely through some audio components (as cymbals often do), but through the Illusion II's analog stage, the cymbals sounded smoother and brassier.

When I played guitarist Larry Carlton's Sleepwalk LP, particularly the cut "Last Nite," I dug the solid groove that Carlton and his fellow Los Angeles and New York studio aces laid down. Why did I dig it, maybe a little more than I normally would? Because the sound seemed nicely focused, with a particularly solid center image. The bass sounded appropriately full-bodied, the keyboards suitably spacious, and Carlton's guitar had lots of body and soul...just as it should. 

After several more albums, I felt I had a pretty good handle on the sound of the Illusion II's analog circuitry; so, to check out the DAC, I switched over to one of the coaxial digital inputs, fed by my Toshiba laptop through the Peachtree Audio T1 USB-to-coax converter. I know L.A. saxophonist Terry Landry's Amazonas (http://terrylandry.virb.com/listen ) well because I was there for the recording session, conducted with audiophile engineer/producer Joe Harley using Sony Direct Stream Digital recording equipment, and the mastering session, performed by mastering legend Bernie Grundman at his L.A. studio. Again, the groove was solid, and the cymbals sounded smooth. So did Landry's tenor sax, which I thought sounded just a little smoother than usual. It was a nice sound, but Landry's tone has a trace more edge and breath in it than I heard here.

Bassist Ray Brown's Soular Energy is one of those CDs that sounds at least pretty good on almost any system, but I thought the Illusion II particularly nailed "Mistreated But Undefeated Blues." The part that the Illusion II got especially right was guitarist Emily Remler's tone, which has plenty of body (like her heroes Herb Ellis and Wes Montgomery) with just a touch of twang. I thought the Illusion II got Remler's badass sound just right. 

Even the (arguably) toughest test track I have, the live stereo version of James Taylor's "Shower the People" from Live at the Beacon Theatre, sounded smooth, natural, and colourless (but in a good way) through the Illusion II. Vocalist Arnold McCuller's solo at the end--a bravura performance that taxes the midrange reproduction of audio components--never broke up or got edgy or bright.

Comparison and Competition

I still hadn't checked out the Illusion II's headphone amp, so I connected my Musical Fidelity V-Can headphone amplifier to the preamp's outputs. This let me compare the sound of the Illusion II's headphone amp to the V-Can. The V-Can is (was--it's discontinued) a modestly priced but respected headphone amp with a nicely low output impedance of five ohms; I figured that, if the Illusion II could match the V-Can's sound quality, that'd be an admirable result.

Look, I am not the guy who gets super-excited about headphone amps; to me, I just want one that's conservatively engineered and has a low output impedance (which, in general, assures the flattest possible frequency response from the headphones). But the first thing I scrawled in my notebook was, "The Krell is OBVIOUSLY better." The Illusion II's headphone amp had an obviously greater sense of space, tighter bass, more detail, more space, and a smoother sound overall; in comparison, the V-Can sounded rather grainy and low-res. Often, headphone amps are added to preamps as an afterthought, without much engineering effort, but it seems Krell put some serious effort into the Illusion II's headphone amp.

An obvious competitor for the Illusion II is the Classé Audio CP-800, I did extensive A/B comparisons between the two preamps, and the main difference was in the mid-treble, of which the CP-800 had more.

Sometimes the CP-800's more prominent mid-treble gave it a more spacious, airy sound. Sometimes it gave a thinner sound. For example, in Steely Dan's classic "Aja," Donald Fagen's voice sounded smooth through the Illusion II but a little dry through the CP-800, as if Fagen could have used a drink of water. The CP-800 had more apparent detail, yet it also made the cymbals on "Aja" sound a little more like aluminum and less like brass. The CP-800's center image also seemed rather spread out compared with the Illusion II's more focused center. Which is better? I think that's a matter of opinion.

All of these differences were subtle, though. On many tunes, such as R.E.M.'s "Cuyahoga" (from the Life's Rich Pageant LP), David Chesky's "Bronxville" (from the Body Acoustic CD), and most of the tunes on the Levin Brothers album, the two preamps sounded almost identical. Should this be a surprise? They're comparably priced solid-state preamps from companies that have been around for decades and have similar engineering approaches.

The Downside

If you like tons of treble detail--perhaps even slightly exaggerated treble detail--I don't think the Illusion II is your digital preamp. I loved its sound, but I'm 53, and I've noticed that the older listeners get, the more they like smoother treble. I could speculate as to why, but I'd just be speculating.

Conclusion

Absolutely, it sounds great. Some audiophiles will likely consider its tonal balance ever so slightly warm but deliciously wonderful, while others may want a little more top end. As for me, I was always very, very happy with the sound of my system when the Illusion II was in it.

 
If the Krell K-300i doesn't end up with a Class A $$$ (for high value) rating in Stereophile's next Recommended Components, the man might as well come and take me away.
Jason Victor Serinus

SUMMARY: I'm hardly the final authority on integrated amplifiers, but of all of them, the one whose sound stands out most in my mind is the Krell K-300i. It has the smoothest, most listenable, and most all-of-one-piece sonics of the lot; it isn't a supreme challenge to move around; and it offers an optional DAC that is surprisingly musical and satisfying for the price. The Krell is also Roon-ready, does well by DSD and MQA, and offers streaming options that some much-higher-priced components lack. There's a round edge to its images that some might equate with the gentlest sprinkling of warmth, but others would describe as listener-friendly. It certainly leaves me smiling. If the Krell K-300i doesn't end up with a Class A $$$ (for high value) rating in Stereophile's next Recommended Components, the man might as well come and take me away. Hey, since that could happen regardless, take a listen soon

I was less than thrilled by Editor-in-Chief Jim Austin's suggestion to review the solid-state Krell K-300i integrated amplifier. I had recently reviewed another similar priced integrated amplifier, the quite different hybrid Aesthetix Mias, and while I ended up liking the Mimas a whole lot, I felt decidedly lukewarm about having to recalibrate expectations for another integrated, especially one that costs far less than my reference Dan D'Agostino Prigression monoblocks (US$38,000/pair) and whose DAC option is a fraction of the price of my reference dCSRossini DAC/ Rossini Clock combination (US$31,498 plus cables). How good could it be?

There's something happening here:
There were also lingering questions about what had happened to Krell after its founders and co-owners, Dan D'Agostino and Rondi D'Agostino, were axed by an investor who, in the words of Krell's present-day COO Walter Schofield, "did not respect the legacy of the brand." Eventually, Schofield reports, the investor "walked away from the company."

Since Dan had already moved on and founded Dan D'Agostino Master Audio Systems, his former wife, Rondi, repurchased Krell in May 2016. After Schofield proposed a new business plan that would address reliability and performance issues, he came onboard as COO. The first all-new product from the re-envisioned and reinvigorated company, the Krell K-300i integrated amplifier, was released in early 2019 as the successor to Krell's US-manufactured Vanguard integrated amplifier.

That I had nothing to worry about (as if it were possible for a Jewish only child not to worry) became clear when I heard the K-300i shortly after its release, during Graham Audio's launch of their LS5/9f loudspeaker at Gig Harbor Audio near Seattle. After spending several hours listening to the speaker with an amplifier that did not do it for me at all, my ears perked up when proprietor Erik Owen switched to a brand-new, hardly-broken-in Krell K-300i. One listen to the difference in midrange (the Krell had a full and warm one, thank God) and top (the Krell's was smooth and extended rather than hard and unwelcoming) made clear that my editor was on to something. A mere two months later, a K-300i made its way to Port Townsend for review.

1119krell.ins

What it is . . . became increasingly clear
While my sample of the K-300i was breaking in, Dave Goodman, Krell's longtime director of product development, gave me a rundown of its key attributes. Goodman, who was working for Sikorsky Aircraft when he discovered Krell's headquarters by chance while driving through an industrial park, has either designed or served as lead engineer for multiple Krell products over his 32 years with the company. Most recently, he designed the K-300i's optional DAC section and was responsible for the final development and implementation of its trademarked iBias technology.

The K-300i's key features include low-negative-feedback, fully differential circuitry, a 771VA power transformer with 80,000µF of capacitance, and a Cirrus Logic CS3318 volume control that runs balanced to ensure that balanced input signals, including those from the DAC, remain balanced until they reach the amplifier's main gain stage. All circuits up to the driver stage operate in pure class-A. Krell claims that this integrated was designed to output up to 150Wpc into 8 ohms and 300Wpc into 4 ohms, with its iBias technology allowing the amp to deliver up to the first 90W in class-A—"without the excessive heat and power consumption of traditional Class-A designs," Goodman told me by phone. (For his complete discussion of iBias and other unique aspects of the K-300i's design, please see the sidebar.)

The front panel includes power, source selection, navigation, menu, and volume buttons; a USB-A receptacle for playback from USB sticks; and an illuminated display. All of the panel's indicators except for volume level were easy to read from my music room's sweet spot, which is located approximately 12' away from my Wislon Audio Alexia 2 loudspeakers. You can assign custom names to sources, adjust volume offset to compensate for different source output levels, choose between variable and fixed output levels, and use the Fixed option to enable a home theater surround-sound processor to control the volume of the left and right front speakers along with all of the other home theater speakers.

1119krell.bac

The Krell K-300i's rear panel includes two pairs of balanced analog audio inputs and three pairs of single-ended analog audio inputs. Given that my reference D'Agostino Progression monoblocks only accept balanced inputs, I stuck with balanced interconnects throughout the review period. Because the K-300i's sole pair of preamp outputs is single- ended, and I didn't want to use single-ended–to-balanced adapters (which might have compromised sound quality),

I was unable to pair it with the Progressions to test it as a stand-alone preamp.

The Krell's loudspeaker outputs come with EU-approved plastic safety fittings, a challenge for bifocal wearers. But once you get the hang of things, it's easy to connect and tighten spade lugs.

A number of the K-300i's rear-panel inputs and outputs are activated with the optional digital module, which uses the ES9028PRO Sabre DAC chip. These include a USB-B input, which accepts signal from external devices such as HDs, NAS drives, and computers; a Bluetooth receiver with aptX; HDMI 2.0a and HDCP2.2 inputs and a single HDMI output; and TosLink optical and S/PDIF coax inputs. An Ethernet input comes standard, as do an RS232 control, baseband RC5 input, and 12VDC trigger input and output.

The DAC, which fully decodes and renders MQA and is a Roon endpoint, decodes PCM up to 24/192 through the rear-panel coax, HDMI, and USB-B inputs; the optical input is limited to 24/96. Higher PCM rates are downsampled. The USB-B input also plays DSD up to 128; DSD256 may be converted to a lower DSD rate, depending on the capabilities of the source device. Both network audio and the front-panel USB-A input work in conjunction with a downloadable ConversDigital mConnect Control app for iOS and Android to decode PCM up to 24/192; those inputs only play DSD64 and will not down-convert higher DSD rates. Depending on the capabilities of your network music server software, you can get around DSD limitations by setting it to down-convert higher DSD rates to DSD64 or to PCM. (Roon can do this.) The mConnect Control app also handles network streaming audio from Spotify, Tidal, Deezer, Qobuz, and vTuner internet radio. It won't wash your windows, however.

There's also a very handy remote control that can select inputs, control and mute volume, adjust balance, and access menu functions. Replacing its two AAA batteries is a pain, however, because it involves using a supplied Torx screwdriver to remove and replace four teeny, easily lost T10 screws.

The K-300i's manual cautions against plugging it into a power conditioner. When questioned, Goodman said, "Krell amps have always had very large power supplies that deliver a lot of current. This means that the power conditioner has to be at least as big as the power supply in the amplifier to avoid limiting power and negatively impacting the sound. The K-300i may be one of our smaller amplifiers, but it has an over-750W power supply. To get everything you can out of it, your power conditioner should be rated for at least 1000W." Goodman subsequently acknowledged that conditioners such as AudioQuest Niagra, which, when run from a 120V supply, can sustain 20 amps for up to 25ms, should be adequate when the K-300i is connected to one of its high-current outlets. Thus, I stuck with my own Niagara 5000, which I use with my reference D'Agostino amplifiers.

Stop: Hey, what's that sound?
My review strategy was pretty straightforward, at least at the start. To evaluate the K-300i solely as an integrated amplifier, I bypassed its DAC section by sending signal from the Rossini DAC's balanced analog outputs to one of the Krell's pairs of balanced analog inputs. After turning the Rossini DAC's volume all the way up, I used the K-300i's front- panel navigation menu to select the correct input. (I could have used the remote control instead, but I kept it on the couch to control volume.) The source was my customary Roon ROCK-equipped NUC, with playback controlled by a Roon app downloaded to my iPad Pro.

I began with Muddy Waters's "Good Morning Little Schoolgirl" from his 1964 album Folk Singer (24/192 MQA, Chess/Tidal). Timbres were virtually neutral with just a touch of inviting warmth, dimensionality was impressive, and the guitar's cleanly articulated dynamic nuances drew me in. The Krell K-300i sounded great.

I was equally enamored of the reproduction of mezzo-soprano Marianne Crebassa's rendition, with pianist Fazil Say, of Debussy's "La mer est plus belle ques les cathedrals," from their album Secrets (24/96 WAV/Erato 564483). The sound was smooth and inviting—I loved the warm highs—the illusion of depth quite good if not breath-seizing, and timbres were spot on. To evaluate the bass, I turned to Mahler's Symphony No.3 by Iván Fischer and the Budapest Festival Orchestra (DSD64, Channel Classics CCSA 38817/ NativeDSD) and King Creosote and Jon Hopkins's "John Taylor's Month Away" from Diamond Mine (16/44.1 FLAC, Deep Six/Tidal/Qobuz), where low bass was impressively tight and clear, with forceful slam. Thumbs up all the way. In short order, it had become clear that listening would be a pleasurable and involving experience and not a mere review assignment.

Out of the blue, award-winning keyboard master Robert Silverman emailed to say he was coming to Port Townsend to give a house concert and wanted to hear my system. When he arrived, we used the Rossini DAC and K-300i to listen to tracks from two of his Chopin recordings: Stereophile's February 2018 "Recording of the Month," Chopin's Last Waltz (DSD128, IsoMike 5606, NativeDSD), which was engineered by Ray Kimber, and Chopin: Polonaise-Fantasie and Four Scherzi (24/96 FLAC, Marquis B07GJ2J9BC, Qobuz). Bob was impressed enough to ask if I thought the Krell might be a good match for his home system.

1119krell.remThen we bypassed the US$31,498 Rossini DAC/Clock combo and auditioned the Krell's US$1000 DAC option. We inserted a USB stick loaded with Silverman's tracks and others into the K-300i's front USB-A port, selected the correct input (Network), and easily controlled playback using the mConnect app I'd previously downloaded to my iPad Pro. Because the Krell's USB-A port can't accept DSD128, we struck out with Silverman's IsoMike recording. Instead, we chose tracks from two other superbly engineered recordings, Crebassa and Say's Secrets and our September 2019 "Recording of the Month," Patricia Barber's Higher (16/44.1 FLAC, ArtistShare AS0171).

Having reviewed both recordings with my reference Rossini DAC, I knew them well enough to note that the K-300i's DAC conveyed less air, transparency, and color contrasts than my reference. The soundstage was smaller and a dearth of harmonics impacted the piano's radiance and vibrancy on the Crebassa, and flattened the sound of double bass on the Barber, but the overall beauty of the music, and its creators' sublime artistry, touched me nonetheless. I hadn't listened to the Barber since writing my review several months before and was delighted anew by the exquisite musicianship of all involved. When we returned to the Rossini, I could hear details such as fingers moving across bass strings that were obscured by the K-300i's DAC.

Days later, I used the Roon app on my iPad to send music from the NUC to the K-300i's DAC via its Ethernet port. On Barber's first two songs, "Muse" and "Surrender," colors were a bit muted, and bass a mite fuzzy. I attempted to hear if those two tracks sounded any different when I used mConnect to play them back from a USB stick inserted into the Krell's USB-A port; if they did, I couldn't hear it. Switching to the first movement of Mahler Symphony No.3 confirmed that, with the Krell's DAC, left/right elements on the soundstage seemed less connected, and the vividness, three-dimensionality, and strong bass that I find so thrilling was diminished. Timbres were still spot on and inviting, but listening was less involving.

Since many audiophiles play their digital files from a computer rather than a dedicated music server, I dragged in a 2017 MacBook Pro, hooked it up to the Rossini via USB, and sent the signal to the K-300i's balanced inputs. With Roon as playback software, the sound on Barber's songs surprised me. While I had expected something noticeably less transparent than through the NUC, the sound was gorgeous, with ideally smooth and correct timbres. Yes, when I ditched the computer and used the NUC instead, highs were clearer, and air and natural sibilance more pronounced and image size increased. The natural radiance and complex overtones of the piano's highs emerged, and I could sense the texture of each note plucked on the bass, but either via computer or dedicated music server (NUC), the sound of the Krell integrated/Rossini DAC combo was wonderful.

Everybody: Look what's going down!
It doesn't take a weatherman with a PhD to know that the wind blows foul when comparing a $1000 DAC to a setup costing 30.5 times more. In the interest of fairness, I enlisted the Mytek Brooklyn DAC+ (US$2195), which has balanced analog outputs but lacks a network connection. It was easy to connect the Mytek to the K-300i and compare its sound to the more-than-14-times-more-expensive Rossini's—the Mytek's highs were a little bright, bass was a mite muffled and diminished, and transparency, depth of color and soundstage, and air were all "less than." However, due to the complexity of my reference system's elaborate noise-isolation scheme—a complexity that compelled Jim Austin to don his starched collar and preach the values of simplicity—directly comparing the sounds of the Mytek and Krell DACs involved more finagling than you would ever want to read about. Ultimately, each had its sonic strong points, but the Krell, which required no additional power cable or space and could accept network signals, triumphed in the cost/practicality department.

1119krell.3

Right before it was time to return from the K-300i to my 6.33-times-more-expensive Progression monoblocks, friend Peter Schwartzman and his audiophile buddy David came by for last listens. Our tracks included the Barber and Mahler, soul vet Bettye LaVette's "Crazy" from Thankful N' Thoughtful "Deluxe Edition" (24/96 Flac/Qobuz), Yello's "Electrified II" from Toy (24/48 WAV, Polydor 4782160/HDtracks), Will.i.am's title track from #thatPower, featuring Justin Bieber (16/44.1 FLAC, Interscope Records UICS-9136/7), and, for that last little bit of pounding bass and blaring brass, Eiji Oue and the Minnesota Orchestra's Keith Johnson-recorded version of Copland's Fanfare for the Common Man from Copland 100 (16/44.1 WAV, Reference Recordings RR-93). David was wowed, and I loved every second of everything I heard. As for Peter, his comment that the K-300i might be the perfect integrated for our doctor/musician friend, Gary Forbes, led me to say that compared to all the other integrated amps I'd ever brought to Gary's for a listen, the Krell's sound was the most neutral, transparent, and satisfying on every level.

Yes, the D'Agostino Progression monos sounded even more neutral than the Krell K-300i. Images were larger, and the soundstage bigger. I heard more depth to voice and bass, and more harmonics on the piano. Barber's hushed singing seemed even more intimate and refined. That recording sounded so exquisite that I wanted to cry. (To those who may doubt these words I say: You don't know me.)

Also with my reference D'Agostino monoblocks, when I turned to one of the recordings I'd reviewed with the Krell integrated, Yannick Nézet-Séguin's version of Mozart's Die Zauberflöte (24/96 WAV, Deutsche Grammophon B003069702), I heard more resonance in the marvelous voice of bass Franz-Josef Selig, which also sounded larger. On Fischer's Mahler Third, it was easy to hear that, at the symphony's beginning, some of the drums were positioned offstage, behind the right side of the orchestra. And to turn from the sublime to the soulful (not that they're mutually exclusive), the guitar on LaVette's "Crazy" sounded even nastier (as it should) with the Krell.

I'm hardly the final authority on integrated amplifiers, but of all of them, the one whose sound stands out most in my mind is the Krell K-300i. It has the smoothest, most listenable, and most all-of-one-piece sonics of the lot; it isn't a supreme challenge to move around; and it offers an optional DAC that is surprisingly musical and satisfying for the price. The Krell is also Roon-ready, does well by DSD and MQA, and offers streaming options that some much-higher-priced components lack. There's a round edge to its images that some might equate with the gentlest sprinkling of warmth, but others would describe as listener-friendly. It certainly leaves me smiling. If the Krell K-300i doesn't end up with a Class A $$$ (for high value) rating in Stereophile's next Recommended Components, the man might as well come and take me away. Hey, since that could happen regardless, take a listen soon, so I can find out what you think before it's too late...

 

"Super fine and detailed, the Foundation made the instruments appear on a deeper stage and at the same time experience Al Jarreau's vocal artistry to the fullest."
Heimkino.- leading home theater magazine,
The first Foundation processor review has appeared in the June issue of Germany's leading home theater magazine, Heimkino. They awarded the Foundation their reference level rating of 1+. Below are some of the translated highlights -
 
"Super fine and detailed, the Foundation made the instruments appear on a deeper stage and at the same time experience Al Jarreau's vocal artistry to the fullest."
 
"The fine pins and needles on the skin where get even more intense, when the Foundation played the first scenes of "Battleship" and "Django Unchained" where it reveals all of its capability repertoire: ranging from extremely delicate to smashing, the processor was able to let the listener enjoy all aspects of home cinema in the finest sound quality."
 
"The Foundation offers Stereo and Multi Channel par excellence and absolute home cinema delicacy. I am convinced, if you listen to the Foundation for the very first time, you will experience that special tingling feeling, and realize, what is possible in your home cinema with the Foundation."
This may be the ‘baby Krell’ – as if one could ever have such a thing! – but it has a big, clean sound that’s as much about clarity and finesse as it is all-out power and drive.
Andrew Everard

REVIEW SUMMARY: We’re a long way from the old idea of hair-shirt hi-fi here: the latest heavyweight integrated amp from Krell’s Connecticut factory comes fully-loaded and then some! 
This may be the ‘baby Krell’ – as if one could ever have such a thing! – but it has a big, clean sound that’s as much about clarity and finesse as it is all-out power and drive. The digital/ streaming section is well worth having, so well does it handle music from network storage and online sources, and it helps make an even more compelling case for what is a particularly fine – and refined – integrated amplifier.

REVIEW: You need to do some serious rethinking on first encountering the Krell K-300i. If you’re expecting a simple device all about massive power and minimalism, you’re going to be disappointed, but for those looking for an amp able to handle all the needs of the modern music listener, this one could just be bang on the money. 
 Of course, being a Krell, that’s bang on quite a bit of money, at least by the standards of the European competition. Available in a silver or black finish, the K-300i comes in at NZ$13,995, with the optional digital/streaming module that was fitted to the review sample bringing the price up to the NZ$15,995 mark. 
 Mind you, writing this review just after returning from Munich’s High End show [see p18], where almost everything I listened to seemed to have one more zero on the price than I’d been expecting, that tag seems anything but outrageous. In a world where the high-end industry seems firmly on a course of ‘premiumisation’, as I heard it described, the pricing of the K-300i almost seems modest.

STATES OF THE ART 
 That’s particularly the case when you consider what you get for your cash. This is the most affordable route into Krell ownership, and the size of the amp is well suited to European tastes, being a standard (ish) 43.8cm wide and just 10.4cm tall. What’s more, while weighty enough at around 20kg, it’s hardly a monster. For all that it does look impressive, especially in the black finish of the review sample – never been too sure of the silver – and with its use of thick metal and substantial construction. And, of course, the K-300i is still made in the USA… 
 As standard the amplifier comes with five analogue inputs – three on stereo RCAs and two on balanced XLRs, with the option of ‘home theater’ bypass on one input to allow it to be combined with a surround receiver or processor. A single set of speaker outputs, on high-quality combination terminals, is backed up with RCA preamp outs, and that’s about as complex as the amp gets, though there is an Ethernet port as standard, alongside RS232, infrared remote in and 12V trigger sockets, to allow it to be controlled in ‘custom installation’ systems. A matching, metal-clad system remote handset is also supplied with the amplifier. 
 It’s possible to rename inputs to suit your requirements, and trims are also available to enable levels to be equalised across all sources. One can also change the IP address of the amplifier when its Ethernet port is being used for control, error reporting, and also for downloading and installing firmware updates

HIGH-END HUB 
 However, things get much more interesting if you specify the optional digital module, which turns the K-300i into a complete digital/analogue hub. Based around an ESS Sabre Pro DAC it gains conventional S/PDIF optical and coaxial inputs, a USB-B port for computer connection, and a front panel USB-A socket to play music from memory devices. There’s also a trio of HDMI sockets – two in and one out – that take sound from video sources using the Audio Return Channel part of the HDMI specification, while passing through 4K HDR video to a suitable monitor. 
While becoming slightly more common on stereo amplifiers these days, such a provision is still a comparative rarity in this sector, even though it’s standard on AV receivers. It’s a welcome addition here, and a sign of the real-world thinking behind this amp. While some may still be lucky enough to have their music system in a separate ‘sound only’ room, many will find their hi-fi sharing space with the TV, and this provision allows very high quality sound to be enjoyed from TV via the main system speakers. 
 The same goes for the streaming capability of the K-300i when fitted with the digital module. Using the dedicated Krell Connect app running on an Android or iOS phone or tablet, or the generic mConnect Control app, it turns into a network audio renderer able to play AAC, ALAC, AIFF, FLAC, WAV and WMA files up to 192kHz/24-bit, as well as DSD up to DSD128, from UPnP-enabled computers and NAS units. It’ll also play online services including Spotify, vTuner Internet radio, Tidal (with MQA decoding for Tidal Masters), Deezer, and Qobuz.
 The K-300i is also Roon-ready, so it can be played to as an endpoint by a Roon core, and has Bluetooth with aptX for wireless music streaming. 
 Although the circuit design is all-new, the basic amplifier technology here is familiar Krell stuff [see PM’s boxout, below]. In short, the amplifier uses the company’s differential ‘Krell Current Mode’ topology from input to output, with an iBias-based power amp delivering a claimed 150W/8ohm, doubling into 4ohm. As PM’s Lab Report makes clear [p43], the amplifier exceeds these claims with ease, and certainly in use the impression is always one of an effortless delivery of the music.

STARTLING SOUNDS 
For those with an awareness only of the mythology that accompanies Krell, the K-300i may come as a surprise, for though it is powerful it is not a fire-breathing amp that storms through everything you choose to play. That’s a common caricature of big American amps, and (usually) an ill-founded one, that the K-300i dismisses with a sound that’s generous, rich and closely detailed, while at the same time having plenty in reserve for the dynamics of the music. 
 One thing that’s very much there from past Krell amplifiers is the solidity and punch of the low-end. Used with speakers able to reveal it, such as my PMC OB1s, the music is built on substantial foundations, but has the agility to propel even the deepest, fastest bass-lines. Play The Who’s ‘Pinball Wizard’ from the original recording of Tommy [Polydor 9861011; DSD64], and the power and deftness of ‘The Ox’ is clearly audible, driving the track on. 
 With Olivier Latry’s wonderful recent Bach To The Future release of the organ of Notre-Dame de Paris [La Dolce Vita LDV69; 96kHz/24-bit], the K-300i comes into its own with the ground shaking pedals. Yet it’s not all about the bass, for the beauty of the ’300i is the way this magnificent low-end is just the underpinning of a sound that’s both absolutely ‘of a piece’ but also packed with internal detail.
 That’s heard in the Latry recording in the sense of this great instrument filling the enormous space, and the way in which air is being shifted to musical effect – not to mention the speed and definition of the notes, and the vivacity with which the timbre of the pipes is revealed. 
 Whether used purely as an amplifier with sources delivering analogue output – in this case a Sony SCD-555ES SACD/CD player and my usual Naim ND555 network player [HFN Apr ’19] – or via its onboard streaming capability, the K-300i is one of those real ‘get on with the job’ amplifiers. Whatever your chosen recording has to give, this amplifier seems capable of delivering it to sometimes startling effect. 
 For example, playing the recent Budapest Festival Orchestra/Iván Fischer Mahler 7 [Channel Classics CCS SA 38019;  SACD/DSD 128], the magnificence of this remarkable recording is served well by the Krell amplifier’s combination of sheer weight and speed. The sound is dramatic and yet fluid, with a big, expansive sense of ambience and presence, and a totally natural-sounding arrangement of the musicians in a sharply-focused soundstage. 
 The brass in the second movement sounds spectacular, with the call and response effect dramatic and believable, while the building orchestra forces see the K-300i maintaining its grip on the music – and the speakers – even when working very hard indeed. 
PUNCHING PERCUSSION 
 As with the previous pieces, the instrumental timbres are realised extremely impressively, benefiting the overall listening experience. And yes, this is a very easy amp to enjoy, not because it’s forgiving of a recording, or smoothing or warming the sound, but due to its complete honesty of musical delivery. 
 Even when pushed hard with recordings of rather less dynamic range, such as OutKast’s punchy ‘Hey Ya’ from The Love Below [Arista 82876 52905 2], the K-300i’s combination of speed and control is nothing short of remarkable. Even when playing at very high levels, the bass stays tight and focused, and everything going on up above is resolved very well indeed. The sound is gutsy, exciting and hard-hitting, but underlying it all is a sense of maturity and refinement.
 Go a bit more audiophile fare with the Rhiannon Giddens/ Francesco Turrisi collaboration There Is No Other [Nonesuch 591336-2], which combines close-recorded female vocals with lovingly-captured instruments without going all John Lewis ad on you – I told you I’d just come back from a hi-fi show – and the K-300i’s combination of focus and generosity of sound is much appreciated. Giddens’ plaintive vocals bounce off the Mediterranean/North African instrumentation on ‘Gonna Write Me A Letter’ to winning effect, the amp punching along the percussion while allowing the other instruments to soar out of the mix. 
 With the infectious piano jazz of Ai Kuwabara, Live At The Blue Note Tokyo [Verve UCCJ-2164; 48kHz/24-bit], the K-300i is able to demonstrate further its combination of low-end extension and speed as a platform on which music is based. It renders Kuwabara’s piano with a delightful lightness of touch, while Steve Gadd’s drums have slam and crispness and Will Lee’s grumbling bass is tight and precise. Add in a fine sense of live atmosphere – got to love that oh so polite Japanese jazz audience applause – and you have a compelling set that’s clearly right up the K-300i’s alley, so well does it deliver it. 

K300i - A hugely talented entry-level integrated amplifier from Krell
What HiFi

OUR VERDICT

Krell’s entry-level amp is brilliant - we can’t think of a rival that’s as accommodating of digital sources while sounding anywhere near as good

FOR

  • Superb detail, dynamics and punch
  • Capable of huge volume
  • Range of inputs
  • Superb build

SCORES

  • Sound 5
  • Features 5
  • Build 5

REVIEW: Krell is one of the founder members of the market sector we now know as the high-end. Back in the 80s, alongside Mark Levinson and a handful of others, it raised performance standards (along with price tags) to deliver some of the finest hi-fi ever made. The brand’s products have remained highly respected over the years, though the business side of things has fluctuated, particularly in recent times. But a change of ownership and a renewed focus on core values has seen the product range rejuvenated. The new K-300i integrated is part of this regeneration and is intended to bring Krell bang up-to-date in terms of connectivity without sacrificing the performance levels with which the company has become synonymous.

Features

This amplifier lives up to our expectations in the metal. It’s an imposing looking unit with a clean but brutal appearance that couldn’t be anything other than a product made by Krell.

We have a complaint here though. That simple control layout isn’t particularly intuitive in use, with input changes needing multiple button presses and changing configuration proving a bit of a faff. Thankfully, the supplied metal remote makes these actions quicker and less tortuous. That remote is nice to hold, though we never quite get used to the rattling as the metal buttons move around in the metal case when the handset is moved.

A basic version of the amplifier is available for NZ$13,995 (incl GST). This is a straightforward 150W per channel analogue integrated with good quota of single-ended and balanced line-level connections. That’s a traditional approach to amplification and is likely to slot into many premium systems without issue. 

Spend another NZ$2000 (incl GST) to get the optional digital module, which is the version we have on test here, and the K-300i becomes a just-add-speakers system. This option has the ability to stream music over a home network and aptX Bluetooth, as well as supporting streaming platforms such as Spotify Connect and Tidal, Deezer, Qobuz and vTuner. 

Then there are the digital inputs. Add the digital module and you get USB, optical and coax connections. The USB will accept up to 24-bit/192kHz PCM files and DSD128 music streams. The coax matches the USB’s PCM rating but, as is usual, isn’t compatible with DSD files. Neither is the optical, but it will handle 24-bit/96kHz music. The K-300i is also MQA compatible and Roon-ready. We can’t think of an alternative that’s as well equipped.

It’s interesting that Krell has also included HDMI connectivity in the form of two inputs and an out. The company recognises that an increasing number of people use their stereo system to improve their television’s sound.

Connecting the amp to a TV’s ARC-equipped HDMI socket means that it can strip the audio track from anything the TV is showing. Including such an input shows surprising pragmatism from such a purist high-end manufacturer and proves its willingness to accommodate the wide range of sources people use today, regardless of the audio quality.

Krell doesn’t have a dedicated streaming control app for the K-300i but recommends the use of mConnect (iOS and Android). It’s free and works well enough but doesn’t feel as slick as dedicated software from the likes of Naim or Linn.

Build

The K-300i feels superbly made. It’s solid and gives off an aura of permanence that’s hugely appealing. Fit and finish is impressive too, just as it should be for the price. There are two colour options, black and silver. This is a heavy amp, weighing at almost 24kg, so be careful when you lift it. Take the Krell’s lid off and it’s the huge 770VA mains transformer and 80,000uF of smoothing capacitance that grabs our attention. That’s the kind of power supply arrangement that makes the claims of the power output figure doubling to 300W per channel into a 4 ohm load all the more believable. We’re also impressed by the neatly designed circuit boards that are fully differential from input stage to output in a bid to improve performance, and a little surprised at how compact the heatsink is considering just how much grunt this integrated has. A relatively small heatsink can be used thanks to the use of Krell’s iBias technology. This keeps the output stage working in Class A but monitors the input signal closely to reduce any power wastage where possible. That doesn’t stop the casework from getting hot though. This amp still needs plenty of ventilation around it to help with heat management. Apart from that, and the relatively large footprint of 44 x 46cm, there’s no issue as far as installation is concerned.

We already know that the K-300i is happy to accommodate pretty much any source you can think of. But if you have a record player, you’ll need an outboard phono stage. While some would prefer such a module to be built-in, the hostile electrical environment inside the amp makes it very difficult to optimise the sound of those very low level analogue signals. 

Sound

This is a highly transparent performer though, so while it’ll work happily with most things across its various inputs it won’t ignore their sonic quality. This is brought home when we play some tunes from our Apple Phone X via Bluetooth. The connection is quick and fuss free, but the results across a range of music from Kate Bush to Olafur Arnalds is listenable at best. That’s not the Krell’s fault, though. It’s a highly resolving product that’s simply showing the input signal for what it is. With Bluetooth, dynamics are limited, as is transparency and resolution. That said, the sound is still entertaining and it does open up your system to playing music that you might never hear in another way. 

Things take a notable step-up when we hook it up to our test network and stream music from our Naim server. Here we play all sorts of recordings, from a CD spec 16-bit/44.1kHz file of Undun by The Roots, right the way through to Hans Zimmer’s The Dark Knight Rises OST (24-bit/192kHz) and Stevie Wonder’s Innervisions on DSD. The K-300i switches between file types seamlessly and quickly, something that isn’t always a given. With Undun we can easily follow the group’s vocals and revel in the thumping beats and smooth flowing rhythms. 

This amplifier resolves an impressive amount of information and organises it with class leading stability and control. Rarely do we come across an integrated amplifier that sounds so composed, regardless of the complexity of the recording.

This aspect is highlighted with the Dark Knight Rises OST. Here the Krell’s bright-lit and strongly etched presentation works a treat. It sounds wonderfully agile and punchy, carrying a big bat while still able to speak softly when the music demands.

We’re pretty shocked by how well the K-300i delivers the soundtrack’s huge dynamic swings and the way it grips our reference ATC woofers to produces what is arguably the tautest bass we’ve heard from any amplifier at this level.

Such is the amplifier’s combination of control and muscle that it sounds right at home delivering massive volume levels through every speaker we tried, from the ATCs to Revel’s Performas.

You can add a wide, stable and wonderfully precise soundstage to the list of positives. It’s easy to pinpoint the position of instruments in the orchestra and their placement remains focused, even at higher volumes. That’s quite some achievement.

Switching to Stevie Wonder’s Higher Ground shows that the Krell has dancing shoes too. While it doesn’t prioritise rhythmic drive in the way of PMC’s Cor, the K-300i still manages to convey the drive and momentum changes in the song well. It’s a fun listen as well as an informative one. The results are equally positive with the other digital inputs, proving that the optional digital module is a good one and great value.

Does it negate the need for other sources? The digital module is certainly comparable in sound quality to the better standalone streamers we’ve heard below the two grand mark, but when we switch to our reference sources – Naim’s range-topping ND555/555PS and SME’sSynergy turntable package (with its integrated phono stage) – it’s perfectly clear that the analogue sections of the amp are capable of doing even better.

With these sources, the Krell’s detail resolution is even better than we expected, though the convincingly even tonal balance and spacious, uncluttered character remain unchanged. We’re now more aware of instrumental textures and notice more of the dynamic nuances in a recording. At its best, the K-300i is good enough to make you think there's no reason to spend more on amplification. 

Of course, compare this integrated with far pricier reference equipment – in our case, Burmester’s 088/911 pre/power – and you’ll hear greater subtlety, an extra dose of transparency and even greater rhythmic precision, but remember, to get that you’ll have to spend many thousands of dollars more.

Verdict

Krell released its first integrated amp, the KAV-300i, back in the mid-90s. That was a terrific performer, and this current version reminds us of that.

The current integrated may be the cheapest amplifier the company currently makes but it still delivers a concentrated dose of the fabled Krell sound. Add the forward-looking feature set and you have something of a high-end bargain.

We doubt there are many times those words have been used to describe a product worth almost nine grand.

SCORES

  • Sound 5
  • Features 5
  • Build 5
the Krell is rather the friend of dynamics and uncompromising tonal neutrality. My appreciation is clearly the Krell.

REVIEWERS COMMENT: in terms of timbres and spatiality: The electric guitar not only sounds a bit more substantial with the Krell Vanguard Universal DAC, but also receives a clearer focus, which appears to be more clearly defined. By the way, what I really appreciate, by the way, draws you a little more convincingly into the picture.

(NOTE - A GERMAN to ENGLISH TRANSLATION via GOOGLE)
REVIEW:
Classic-traditional high-end brands with a particular aura - Krell is certainly one of the exclusive groups. Founded almost 40 years ago by Dan and Rondi D'Agostino and finally taken over by a group of investors, the Americans have an eventful vita - especially with them Over the decades, the construction of weighty amplifiers earned an almost "iconic" reputation: accordingly, a Class A amplifier - the Krell KSA 100 armoured with "studio handles" - marked the starting signal. The topic "D / A converter" had not slept in the late 80s, but also. Nonetheless, the Vanguard Universal DAC being tested here is "Krell's first standalone DAC for over 20 years," as the manufacturer 

Where "standalone DAC" basically falls short: The Krell Vanguard Universal DAC is equipped with an Ethernet interface and therefore a genuine streamer / network palyer . The streaming module used was not an off-the-peg solution. A particularly high-quality clock or high clock precision and low interference were in the development of the module, which was done in cooperation with an external specialist, rather high up in the specification.

It is still often underestimated that the allegedly profane streaming process, in addition to the actual conversion and subsequent analogue signal processing, has crucial relevance for sound. For example, the actual significance can be impressively demonstrated by high-quality streaming bridges à la Auralic and even more by the SOtm-sMS-200ulta.

The word standalone DAC takes a bit too far, but perhaps also: If many consider a USB-B interface to be such a device for granted, it shines through in our test persons by absence. For this, you can plug in a USB stick or a hard drive to the American via the front USB-A socket, which makes a "Vanguard Universal DAC Server" appear in the local network - so an extra NAS server is not absolutely necessary. By means of S / PDIF (optical + electrical) or HDMI, the Americans can also be wired. Last but not least, the Krell Vanguard Universal DAC can also be accessed wirelessly via Bluetooth aptX . Analogously, the music data are then released both via RCA and XLR, as a digital output is in turn HDMI available.

Digital + analog

On the chip side, Krell has decided on the hip, high-end 32-bit ESS9018-DAC, which would be called even faster, but nonetheless converts up to 192 kHz / 24 bits in the Krell Vanguard Universal DAC (Toslink naturally has a maximum of 96 kHz).

On the network side, the Krell Vanguard Universal DAC is easily compatible with local UPnP / DLNA servers (NAS). In my experiments, a MinimServer established by my SOtM sMS-200ultra served as data provider. Not only did he allow me to control my iPad with the "mconnect" app recommended by Krell, but he could also easily navigate via the "Bubble" -enhanced Android tablet - including volume control. In addition, the Krell is prepared for Roon (Roon Ready), hooks up with Spotify, Tidal and Deezer and dives on command in the depths of the Internet radio.

But the Krell is not a pure Digitalo, but also has an analogous soul and can therefore serve as a volume-regulating preliminary stage: The discretely constructed Class-A circuit domain of the Vanguard Universal DAC would, according to Krell, correspond to those in the precursor Krell Illusion 2 is used. Almost four years ago, I personally hosted the top model, Krell Illusion , one of the best preamps I ever heard - extreme undeferencedness and permeability are among its cardinal virtues. The analogous kinship between Universal DAC and Illusion 2 also fits the fact that the power supply of the DAC is classic-audiophile: Instead of a switching power supply, this is based on a weighty toroidal transformer.

If you want, you can also deactivate the volume control - whereby we would then be able to make the menu settings of the Krell Vanguard Universal DAC, which can be fitted with the included metal remote control pawl, also for self-defense or home improvement: Adjustable input sensitivities, among others Contrast of the display or its automatic switch-off (15 to 129 seconds). Software updates are also possible.

In practice

Speaking of display: So robust, high-quality and no-frills professional designed the Krell also comes along - yes, somehow the American exudes something pleasantly serious -, the approximately 12.5 x 2.25 inches measuring "display slot" would be next to the missing USB-B - a point that could be criticised in terms of "practicality". Not even at all, because you actually have to sit in front of the rack with the remote control, if you want to clear your mind in the menu settings - after all, you rarely have to do it anyway. The on the right in the upper line of the display urged Laustärkeanzeige is already more relevant: handed them from a few meters distance rather guessing, especially if you look rather from above on the lower racket-populating device.

Speaking of display: So robust, high-quality and no-frills professional designed the Krell also comes along - yes, somehow the American exudes something pleasantly serious -, the approximately 12.5 x 2.25 inches measuring "display slot" would be next to the missing USB-B - a point that could be criticised in terms of "practicality". Not even at all, because you actually have to sit in front of the rack with the remote control, if you want to clear your mind in the menu settings - after all, you rarely have to do it anyway. The on the right in the upper line of the display urged Laustärkeanzeige is already more relevant: handed them from a few meters distance rather guessing, especially if you look rather from above on the lower racket-populating device.

Krell Vanguard Universal DAC: hearing test & comparisons

Sometimes, some manufacturers surprise by saying that they like to break with sound philosophies that have been cultivated in the past: Marantz comes to mind, for example, a manufacturer who now has some quite straight and in my opinion excellently tuned components in the portfolio, like the recently tested PM8006 or the slightly older NA8005 . With regard to the coordination of modern Krell components - the S300i - I have quite a clear expectation: neutral tuning, yet deep bass, high dynamics and resolution.

But let's just plug in the Krell Vanguard Universal DAC and hear what he has to say about such expectations. I tested mainly via LAN, the server (MinimServer) as I said my SOtM sMS-200ultra (with power supply upgrade to) by means of plugged USB hard drive, which is connected together with the Krell DAC via a Lancom switch to the network , For comparison my Linnebberg, a DIDT DAC 212SE, my NuPrime DAC10H and my "good old" Electrocompaniet ECD2 ready. In contrast to the Krell all pure DACs, which are fed by the aforementioned SOtM - not in its function as a mere server, but as an audiophile renderer / network player - via USB.

The listening tests with the Krell Vanguard Universal DAC were mainly done via LAN

First of all, for the sake of completeness, anyone who thinks that it is close to such a streamer / DAC combination like the Vanguard Universal DAC by means of a "normal" computer backed up by a good media player plus a very good USB DAC, is mistaken. Even my formidabler, after all 4,400 euros heavy Linnenberg DAC it in direct comparison to the Vanguard schlieriger, spatially less focused approach, it is supplied by my sound-optimized Windows computer via USB-B with music data. What makes it clear, as mentioned above, that it not only depends on the DAC, but also on its digital player. And to conclude that Krell has indeed audiophile care when integrating the streaming module in the Universal DAC.

But even in the direct A / B comparison between a combination of NuPrime DAC-10H and SOtM-sMS-200ultra and the Krell Vanguard Universal DAC, differences can easily be heard: The fine, sustain-rich, room-filling pelvic sounds in Øystein Sevåg's "Hanging Gardens" (album: Bridge, listen to it on Amazon ) gives the Krell a noticeably more filigree and open feel. As if he climbs some more sprouts in the direction of super-high, which certainly adds a little mite to his slightly higher "fine pixeliness" and suppleness. In the further course of the piece, a soprano-saxophone, flute and piano catching a succinctly captivating sound finally seems to be more open and even bigger, indeed more involved, when it comes to the Krell DAC. Sure, we are dealing here with digital sources, said differences do not appear so clearly, as is to be expected when comparing different speakers, but especially fall over good equipment directly in the ear.


Next we connect the Electrocompaniet ECD 2 with the SOtm-sMS-200ultra. By the way, the SOtM is a very practical, incorruptible and thus very helpful tool, not least for comparisons like this one, due to its variability and highly accurate, unadulterated sound characteristics. The Norwegian ECD 2, however, is no longer the very youngest, but especially in terms of (fine) dynamics and high-openness still up to par and across all price categories a good benchmark. Immediately countered, it confirms that the Krell Vanguard Universal DAC is one of the components linearly penetrating to the very highest levels. And if he draws the upper layers as free of whitewashing or special golden shimmer as the Electrocompaniet, I feel the tonic of our test subject tonal even more harmonious involved in the rest of the action and tonal colour something organic: pelvis and hi-hat in Dysrhythmias "Running Towards The End "(Album: Test of Submission, listen to Amazon ) come across the Krell succinctly as it pertains to pure doctrine, but in comparison, as if freed from a recent diffuse note and a bit" deburred "on. Dynamically, the Electrocompaniet / SOtM station wagon and the Vanguard Universal DAC meet at eye level and can be counted as fast over there as one of the fast representatives of their guild. In terms of Basstiefgang I would also turn out no differences. Rather REVIEW: in terms of timbres and spatiality: The electric guitar not only sounds a bit more substantial with the Krell Vanguard Universal DAC, but also receives a clearer focus, which appears to be more clearly defined. By the way, what I really appreciate, by the way, draws you a little more convincingly into the picture.

If you put the DiDiT DAC 212SE in the rack and network it with the SOtM player shoots you after a few comparison rounds with the Krell a "more a matter of taste" in mind: In terms of tone purity, differentiation and spatial definition of instruments plays the Recently Benjamin Baum aptly described DiDiT at a similar high level as the Krell Vanguard Universal DAC. Nonetheless, both devices are aimed at different types of listeners: The tonally slightly warmed, thought-out DiDiT will certainly appeal more to the "relaxed pleasure listener", the Krell is rather the friend of dynamics and uncompromising tonal neutrality. My appreciation is clearly the Krell.

Particularly exciting I find the final duel between the Krell Vanguard Universal DAC and my top reference Linnenberg Telemann, with said SOtM sMS-200ultra including power supply upgrade for some time without my rack is inconceivable. In the test of Martin Mertens from February of this year it says to the Telemann: "Resolution, fine drawing, detail reproduction - these aspects brings the Telemann to a new level", even in the bass is offered extraordinary control and accuracy and "rhythmically mimic the Telemann the model boy" .

In Blur's "Ice Cream Man" (album: The Magic Whip, listen to Amazon ) fall first in the four-four beat to one beat, enriched with plenty of sustain bass impulses: In terms of depth, vehemence and precision both solutions sound absolutely official and at eye level. Incidentally, the slightly idiosyncratic bass beats are a real stumbling block - they are dynamically contoured and bring to the listener in the right tonal dose - which is certainly not easy for a hi-fi, as I know from many listening sessions. Both duelists nevertheless solve this exemplary.

Even in terms of fine resolution there is virtually stalemate: The subtle metallic sounds at the beginning of the title, as if rubbing coins, the rather inconspicuous shaker on the left channel or the abruptly sinking cymbals: side issues, fine textures and nimble transients have both the Krell as the Linnenberg / SOtM combo absolutely on it, certainly not least because of their each absolutely free of grisly-pure, focused style of play. At the same time, the Linnenberg / SOtM team shows a somewhat more fluid gait, which nevertheless does not detract from its precision and dynamics. The Vanguard Universal DAC Krell, on the other hand, places a little more emphasis on the attack phase of notes, which makes it a bit crispier and more masculine, which does not affect its long-term suitability and naturalness either.

This integrated amplifier lacks almost nothing - actually it is almost an all-in-one device. The Krell pulverises my prejudices almost from the first note, it fills me with great joy when listening to music.
Stephan Schmid

SUMMARY: The fact that the Krell pulverises my prejudices almost from the first note fills me with great joy when listening to music. The K-300i is clear, stocky in the low-frequency range, and that must be a Krell amp, but it is not a clumsy fuss, but does its job with surprisingly fine flair. Nice to hear from the Viennese cult band Wanda. The relaxed drive of the music and the sometimes shabby vocals of singer M.M. Fitzthum called Marco Michael Wanda is reproduced very prominently by the K-300i. Despite the mumbled Viennese singing in "Columbo" on the album "Niente", the lyrics were easy to understand, and the music encouraged me to bob my feet. To be honest, I wouldn't have believed the Krell that way. Incidentally, I had this "urge to move" regardless of whether the player was my turntable with phono-pre via ZenSati NF cable or the music server with D / A converter via ZenSati XLR cable. The K-300i also showed its class in the classic "The Girl From Ipanema" by Stan Getz and Joao Gilberto (from the album "Getz / Gilberto feat. AC Jobim") from 1963. It started a bit fuller than usual, but then Astrud Gilberto came in: clear as a bell her voice came out of the depths of the room, the saxophone was of an incredible intensity - this shows the ability of the Krell to reproduce midrange with an incredible enamel.

REVIEW: The Krell K-300i, is dressed in a very chic dress, is fist-thick behind its aluminium front panel. This integrated amplifier lacks almost nothing - actually it is almost an all-in-one device.

When I took my first steps as a hi-fi enthusiast in the 80s, like many of my like-minded fellow students, I moved through the Berlin studio scene to at least take a look at the prized items on the HiFi Olympus or a demonstration with them to experience. At that time, one of the products we mostly discussed was the power amplifier from Krell - large, powerful, Class A with unimaginable performance. Everyone wanted to hear them. Then one day I enjoyed it - and was extremely disappointed. "Not being able to walk with power" was my first thought, and I had hit the sound experience quite well. The Krells brutally pushed loudspeakers from different manufacturers, triggered primal forces in the bass cellar, but musically they did not want to meet my expectations: no flow, no swing, limited space, no musicality. When the K-300i announced itself, I thought that it certainly wouldn't hurt to experience a Krell of today and check whether anything could be changed in my posture.

With the K-300i, I now have an amplifier in my listening room where I am initially not sure how to deal with the K-300i with my (preliminary) judgment from over 30 years ago. So let's take a look at what the AMP made in USA has to offer. With its 44 centimetres in width and just over ten centimetres in height, the K-300i is almost classic if it weren't for its depth of 46 centimetres. These are dimensions that not every rack can handle. A look inside provides the explanation: A neat 700 VA transformer and the power amplifier section next to it, including solid heat sinks, take up a good two thirds of the space. In order to accommodate the prepress and the digital board here, you need the sprawling depth.

The front is adorned with the power button on the left, which brings the amplifier from stand-by mode to life or brings it back to sleep, as well as seven buttons with which the K-300i can be controlled and various settings can be made. To the right of the amplifier's name, which is prominently placed on the curved front, there is an excellently readable display as well as two buttons for volume control and a USB input. The beautiful back enchants with sensible connections on the classic amplifier side: Two inputs in XLR format and three cinch connections do not burn anything, a cinch preamp output and a pair of really well-made speaker terminals round off the positive impression. The rest of the space is occupied by the connections for the optional digital board. For this, Krell charges a surcharge of 2,000 euros, which at first glance is quite sporty, but this digital board has it all, because it is not a pure D / A converter board like most competitors, but in the actual sense a network streaming board.

The digital board can be connected via optical and coaxial S / PDIF cable, via USB-B port and via Bluetooth in the aptX standard. Krell also offers AV fans access to the amplifier. Three HDMI inputs are available here, two of which are intended for source devices. This also gives concert videos an impressive backdrop in terms of sound.

With this digital board, aptX standard connection can be established via optical and coaxial S / PDIF cable, via USB-B port and via Bluetooth. Krell also offers AV fans access to the amplifier. Three HDMI inputs are available here, two of which are intended for source devices. The third HDMI input is intended as a connection to the television and is designed as an “ARC” (Audio Return Channel) version. This makes a sound bar obsolete, because the television sound can be played back in the highest quality via the stereo system. The icing on the cake of this digital board is the music streaming option: connected to the home network via Ethernet cable, the K-300i acts as a full-fledged network player via Roon or various UPnP apps. Streaming services such as Qobuz, Tidal or Spotify can also be used in this way.

Serious option

Technically, the converter section is also up to date. With the ES9028Pro converter from the 32-bit reference series from ESS, the K-300i is able to convert the incoming signals with 24 bit / 192 kilohertz (the optical connection is an exception here) and via the HDMI Process input even DSD. For the Krell, Highres signals of any kind are not a problem, and so the streaming capability is not a slimmed-down addition, but a really serious option to get by without any additional streaming components in the system.

However, the most important thing of a full amplifier is the quality of its amplifier section, and here Krell has decades of experience. The K-300i has the self-developed iBias circuit in the power amplifier. With this innovative feature, the power amplifier working in Class A mode is to be taught more efficiency and less heat generation. The tonal merits of a pure Class A amplifier should be preserved. I have never seen a Class A power amplifier with a power rating of 300 watts at 4 ohms in such a narrow housing. The heat generated is dissipated using a large heat sink and two quiet fans.

The third HDMI connection (Out) is intended as a connection to the television and is designed as an »ARC« version (Audio Return Channel). This makes a sound bar obsolete, because the television sound can be played back in the highest quality via the stereo system.

Even from a distance, the information on the display can still be read easily. If the remote control is not at hand, the volume can be adjusted using the two push buttons.

The Managing Director of the German Krell sales department, also provided me with power cables, NF and XLR cables from the Zorro series from ZenSati. Without question, these cables fit very well with the K-300i due to their homogeneity. After I looped the Krell into my system, I was very excited to see whether my attitude towards Krell amplifiers would manifest itself or whether the K-300i would teach me otherwise. Every amplifier gets me used to a few days in which it is only responsible for the background sprinkling. But even with this task, the K-300i made a remarkably positive impression. He transported straight voices even at low volumes with a melt that really turns you on. Sure, that's the chocolate side of a well-made Class A circuit, but the ability of the Krell goes much further than I expected.

The new age

The fact that the Krell pulverises my prejudices almost from the first note fills me with great joy when listening to music. The K-300i is clear, stocky in the low-frequency range, and that must be a Krell amp, but it is not a clumsy fuss, but does its job with surprisingly fine flair. Nice to hear from the Viennese cult band Wanda. The relaxed drive of the music and the sometimes shabby vocals of singer M.M. Fitzthum called Marco Michael Wanda is reproduced very prominently by the K-300i. Despite the mumbled Viennese singing in "Columbo" on the album "Niente", the lyrics were easy to understand, and the music encouraged me to bob my feet. To be honest, I wouldn't have believed the Krell that way. Incidentally, I had this "urge to move" regardless of whether the player was my turntable with phono-pre via ZenSati NF cable or the music server with D / A converter via ZenSati XLR cable. The K-300i also showed its class in the classic "The Girl From Ipanema" by Stan Getz and Joao Gilberto (from the album "Getz / Gilberto feat. AC Jobim") from 1963. It started a bit fuller than usual, but then Astrud Gilberto came in: clear as a bell her voice came out of the depths of the room, the saxophone was of an incredible intensity - this shows the ability of the Krell to reproduce midrange with an incredible enamel.

If the music server is connected directly to the D / A converter via S / PDIF cable, the sonic signature changes a little in the direction of »Prussian«. A slightly brighter, stricter signature goes hand in hand with switching to the internal D / A converter - this has nothing to do with better / worse, no, with some recordings simply better audibility is the result. The live recording “Concerti” by Paolo Conto wins a little bit. The musicians are localised more clearly on stage, and Contes voice is easier to understand. Interestingly, the spatial representation does not change - it is rather compact in width and realistic in depth. If you want to explore the bass capabilities of the K-300i, you should put on "Pili-Pili" by Jasper van't Hof (on "Pili-Pili"): The K-300i presents the percussion explosions with force and drive and leaves the other Instruments, especially van't Hoff's piano, the due place and does not cover a single note.

This Paolo Conte concert is very successful in terms of sound and atmosphere. A good system makes you a listener in the present, even though the recording was made three decades ago.

With the K-300i amplifier, Krell has created a multifunctional control centre, an all-in-one first-class concept. Everything that is needed in digital processing - network players, AV capability, digital inputs, high-speed streaming - is available and offers the buyer considerable added value. But basically, the K-300i is and remains a first-class amp that knows how rhythm and drive first catch the listener and then indulge them permanently.........  Stephan Schmid

I've heard in most amplifiers. For those who seek the best quality in amplification for their home theaters, the Krell Theater 7 sets a new standard at this price point.
Myron Ho

CONCLUSION: "While the Krell Theater 7XD is not a traditional Class A amplifier because of its dynamic bias, the Krell Theater 7 sounds more like Class A than I've heard in most amplifiers. For those who seek the best quality in amplification for their home theaters, the Krell Theater 7XDsets a new standard at this price point. We all like a good comeback story, and the Krell Theater 7XD certainly is setting up a nice future for this lauded brand.” - 5 STAR PERFOMANCE RATING

EXTENDED REVIEW: "Krell has had its share of ups and downs in the past few years, and not just of the managerial sort that recently resulted in recent new management and a solid attempt at reinvigorating the brand. Nearly a decade ago, the company made quite the statement amongst its better-heeled, die-hard with its $30,000 Evolution 707 AV preamp and similarly priced associated amplification. It also more recently launched the Foundation line, which represented a new strategy of bringing Krell's inimitable build quality and performance to a larger pool of consumers at more attainable price points.

At its heart, though, Krell has always been a company whose reputation lay not just with its build quality, but also its technology. Technology like Class A iBias topology, for example, which first debuted in Krell's new flagship and Chorus line of amplifiers as a novel way to provide coveted Class A sound quality while dealing with the topology's known issues: excessive power consumption and heat dissipation. The new Krell Theater 7 seven-channel amplifier benefits from a trickling down of that technology to a lower price point. At $7,500 retail, the Theater 7 is Krell's entry level seven channel amplifier. Total output is rated at 120 Watts per channel RMS into 8Ω with two channels driven and 105 Watts per channel RMS into 8Ω with all seven channels driven. With 4Ω loads, those numbers go up to 210 and 140 Watts, respectively.

Setup

As you might expect, given that the Theater 7 is a multichannel amp, setup isn't overly complicated. Analog inputs consist of seven XLR balanced or single-ended RCA connectors, and the outputs comprise seven sets of densely packed binding posts. The amp is reasonably beefy at 70 pounds, so you'll need to be careful not to stack it on top of other gear. And stacking other gear on top of it is an equally bad idea, as it needs some room to breathe.

Perhaps the most surprising thing about the Theater 7 is its Ethernet connection, which can be used to monitor the amp's performance and protection circuits, tweak presets like display brightness and timeout, mute individual channels, and update the firmware. You can also set up email alerts to automatically alert you or your dealer to issues pertaining to excessive current, overheating, short-circuiting, etc.

Performance

Krell is known for big, powerful, bass-forward amps, so my first question when sitting down to evaluate the Theater 7 was whether or not it could live up to that reputation at this lower price point. As such, I gave the Theater 7 a torture test right off the bat by playing some movies without a subwoofer and setting my Salk Signature Soundscape 12 speakers to full range. This effectively meant the 12-inch woofers on my Salks would serve as the de facto dual subs for the system, and the Krell Theater 7 would be driving that along with all the other channels simultaneously.

I pushed volume up to THX reference levels on exceptionally bass heavy soundtracks like The Dark Knight and Tron: Legacy. The bass sounded tight and well controlled with both explosions and percussion-heavy music, physically rumbling my innards. Simultaneously, dialog and music were crystal clear. At no point did I hear the Krell stress or strain, a true indicator of its top-shelf build quality and design integrity.

On multichannel music, the Krell offered a rich and refined sound, very much like a traditional Class A amplifier. Unlike many traditional Class A amplifiers, which can double as a grill for your steaks, the Krell was merely warm to the touch. As you would expect from Krell, there was no audible distortion, even with high-resolution music. The Krell Theater 7 was quite neutral sounding, but maintained a musicality that I found soothing.

High Points

The Krell delivers on the promise of Class A sound with little to no wasted heat.
The Krell Theater 7 has power and current to spare.
The Theater 7 delivers the build quality and fit-and-finish we all expect from Krell. That does make it more expensive than other brands' amps with similar performance, but it's nice to know that no corners were cut.
The inclusion of balanced inputs is very much welcomed. This could come in particularly handy if your amp is installed some distance away from your preamp, for whatever reason, or if you know you have issues with interference in your listening space.

Low Points

The Theater 7 could benefit from some built-in handles, the likes of which you find on other power amps of this heft. Beware lifting this behemoth without using your legs. Better yet, make your dealer install it. (really a bit old hat dont you think?)

Competition and Comparison

The ATI Signature 6007 amplifier costs $500 more at retail and will provide you more power still with all channels driven, should you need it. The ATI is a very nicely designed Class AB amp, so you'll be giving up on the warmth and purity of tone you'd get from the likes of this Krell or (at lower listening levels) Pass Labs, etc. The ATI also weighs 136 pounds, so unless you happen to be the reigning World's Strongest Man, you may find it difficult to install by yourself.

In Krell's own lineup, the Chorus 7200 costs $3,000 more, but offers an extra 100 watts per channel. The Monoprice Monolith 7 is a great value, being priced at a significantly lower $1,600 price point, but you will most likely find it doesn't quite rival the refinement and headroom of the Krell. It's great for the money, it's just not Krell great.

Conclusion

While the Krell Theater 7XD is not a traditional Class A amplifier because of its dynamic bias (iBias), the Krell Theater 7 sounds more like Class A than I've heard in most amplifiers. For those who seek the best quality in amplification for their home theaters, the Krell Theater 7 XD sets a new standard at this price point. We all like a good comeback story, and the Krell Theater 7XD certainly is setting up a nice future for this lauded brand.”

Moreover, the sound of the pairing of the Krell Illusion ll preamp and Krell Duo 175 stereo amp I liked much more than quite hard and cold sound of some older models of the mid-1990s — beginning of 2000-ies.
Webblack.net

SUMMARY: Krell amplifiers have long earned the reputation of "kings of bass", and I don’t deny myself the pleasure to start the program listening several albums with excellent written bass parties. Well, the reputation has been brilliantly confirmed. For example, the title track of the album Pat Travers «Crash and Burn» sounded so powerful and even frightening that after graduation I had to take a short break to reconfigure the perception of less aggressive genresIn the transition to the classical repertoire Krell is the ability to control the acoustics resulted in an extraordinary transparency, which were presented to the most complex fortissimo. Needless to say, «the Firebird» by Stravinsky, I was again stunned and plunged into the thrill, however small violin compositions of Haydn sounded appropriately heartfelt and beautiful. Despite his heroic strength, set can sound soft and gentle, when needed, with very believable voices. Three-dimensional scene, so appreciated by audiophile, Krell manages to pair perfectly with the amendment, of course, on your speaker system and room. In General, the performance of the admittedly gorgeous.

EXTENDED REVIEW: The Illusion II preamplifier and power amplifier from Krell Duo 175 - The name of the American company Krell has long been synonymous with sound of the highest level. The next generation of music lovers discovering branded equipment, and all as affected the outstanding quality of sound and workmanship. However, recently the company went through a rather difficult stage.

Despite the fact that the first Krell amplifier under the brand saw the light in 1980-m to year, in recent years, the company had to work hard to maintain a high level of confidence in their products, which has already become habitual for her. Suffice it to say that pre-owned Krell amplifiers still enjoy huge success with buyers willing to pay for them a sum in excess of the original price! What happened? This is due, firstly, with the departure of the Krell, the founder and chief developer of the company Dan D’agostino behind the creation of all classical models of the firm. (PLEASE NOTE- the 2 original engineers who were really responsible for the vast majorty of their designs are still with Krell). Secondly, with ever-increasing user requirements to functional equipment equipment class High End. Component construction principle of the stereo is still not questioned, however, to meet today, for example, pre-amplifier no DAC, and even the wireless module and the streamer becomes more difficult. How successfully managed a team of Krell with upgrading and maintaining the quality of the sound at the proper level? We will check this with the example of the set consisting of the preamplifier Krell Illusion II stereo power amplifier Krell Duo 175.

For each generation of its technology Krell designers continue to invent new forms. The next iteration of stereo equipment, the company also got his very recognisable, though not too original looking. Silver paste with the lights on the center of the front panel came in mind not all inveterate audiophile, however, one must admit that now equipment company looks much more modern, and not as brutal as the classical model. However, the main changes are connected not with the design of the front panel, and hidden inside.

Krell Duo 175

The main stars of the model range of the American firm has always been the power amps, so with them we will start with the introduction kit. Presented to test the stereo amplifier takes an intermediate position in the hierarchy between the entry-level devices and top-end Solo 375 monoblocks.

Power output is claimed at 175 Watts per channel into 8 Ω, actually, hence the number in the title. As we would expect from a Krell amps, when operating at 4 ohms output power is doubled to 350 Watts. That is, as in the previous models of the firm, output stages work in pure class A? Not really. And here we come to the main innovation introduced in the design in recent years. The company’s engineers came up with a cunning move, allowing you to keep all the advantages of operation of the amplifier in class A, but significantly reduce power consumption and heat. This is achieved through the intelligent circuitry iBias, analysing in real time the level of the current given to the load, and adjusts accordingly the current of rest. As a result, the transistors continue to always remain open, however, the flowing current varies depending on actual load. I must say that trying to do something similar has already been attempted by other manufacturers, but the implementation suggested changing the quiescent current depending on the input signal, which did not give the desired result, primarily, from the point of view of sound quality. Looking ahead, we can say that the Krell engineers had achieved the seemingly impossible.

Another innovative feature is the presence on the back of the RJ45 port. It allows you to manage and control the many parameters of the amplifier via a network interface. Of course, this requires you to connect the device to your home network, where he will be assigned its own iP address. In addition, if you encounter any problems the company will be able to remotely read the code errors and make recommendations for its elimination. Frankly, this feature is unlikely to be commonly used by normal users, however, the mere fact of its existence says about the company’s commitment to meet the requirements of the digital era.

On the rear panel are one pair of speaker terminals and the RCA and XLR connectors for balanced and conventional connections. What is less familiar is the presence of four fans for forced cooling of the output transistors. Previously, the company relied solely on the massive passive radiators. However, thanks to the innovative control scheme, the current peace, to intervene in the case, the fans have rarely. In the rest of the Duo 175 is a classic two-channel amplifier Krell, powerful and imposing.

Krell Illusion ll Preamp / DAC:

The second component of the kit — Krell Illusion II, the younger of the two available in the product line of the company pre-amplifiers. Often when first turned on modern audio equipment with a digital filling the user has to spend some time to understand all the settings and assigning inputs. In the case of Krell Illusion ll I listen to ten seconds after activation.

The front panel contains the activation keys for each of the inputs, adjust the volume level and channel balance, as well as navigate through a short menu. The included remote control is traditionally enclosed in a housing of machined aluminium and is covered with small buttons. The digital part of the pre-amplifier is built on the ESS Sabre chip and is able to work with LPCM signal with parameters 24 bit/ 192 kHz. In General, the apparatus is easy to handle and intuitive.

Sound

Audition set it was decided to hold in a pair of Studio monitors, the legendary JBL 4345. Despite the fact that they have high sensitivity, their 18-inch bass still needs good control. And horn mid-range section will allow you to easily identify any flaws in the amplifier part proper transmission of voices and live instruments. As the source was the CD player Bryston BCD-1 and the turntable in the VPI Classic. Switching between pre-amplifier and power amplifier were carried out in symmetric and asymmetric Protocol. In the end, there was a preference for the balanced option.

Krell amplifiers have long earned the reputation of "kings of bass", and I don’t deny myself the pleasure to start the program listening several albums with excellent written bass parties. Well, the reputation has been brilliantly confirmed. For example, the title track of the album Pat Travers «Crash and Burn» sounded so powerful and even frightening that after graduation I had to take a short break to reconfigure the perception of less aggressive genres. If we go back to work a couple of amps on the bass, it is quite obviously the following to improve the sound quality in this range is possible only by acquiring top-end kit from Krell, and that — not the fact that the result will definitely justify the difference in price. All proposed system of records, including Metallica, classic albums Rush, cut by the legendary Bob Ludwig, and challenging enough to play Them Crooked Vultures, was played out almost perfectly. Amplifiers effortlessly disassembled into components and re-assembled in a single unit loud drums and bass guitars and hi-hat don’t forget to sparkle with silver.

In the transition to the classical repertoire Krell is the ability to control the acoustics resulted in an extraordinary transparency, which were presented to the most complex fortissimo. Needless to say, «the Firebird» by Stravinsky, I was again stunned and plunged into the thrill, however small violin compositions of Haydn sounded appropriately heartfelt and beautiful. Despite his heroic strength, set can sound soft and gentle, when needed, with very believable voices. Three-dimensional scene, so appreciated by audiophile, Krell manages to pair perfectly with the amendment, of course, on your speaker system and room. In General, the performance of the admittedly gorgeous.

Since I have had a chance to listen to the work of JBL 4345 monitors paired with earlier generations of Krell amps, it was difficult to refrain from carrying out direct Parallels. 
In my opinion, the difference in sound with the new model number appears no more than between all of the previous generations, designed by Dan d’agostino. That is to say that the use of iBias has led to the loss of signature handwriting is impossible. Moreover, the sound of the pairing of the Krell Illusion ll preamp and Krell Duo 175 stereo amp, I liked much more than quite hard and cold sound of some older models of the mid-1990s — beginning of 2000-ies.
Well, about the bass has been said enough above.....

Everything about this amp is absolutely superb
Bob Furstenberg

I submit that they’ve just returned to what made them great in the first place, bringing it up to date with the best advances in audio technology that have come our way in the last few decades.
Jeff Dorgay

SUMMARY: The raw emotion that generated so much excitement over this brand in the 80s is back in spades, yet without losing that magic, there is more low level detail, and more refinement. This is a tough combination to master, yet Krell has. It’s like taking a car with a great paint job, wet sanding it with 2500 grit sandpaper and then buffing to a higher luster than you thought possible – yet there you are.

EXTENDEDE REVIEW: My journey with Krell goes back. Way back. All the way back to the original KSA-50 and PAM-5. I’ve always liked the brand, and thought the name was super cool.

Plus, Krell was always a serious engineering company, and their products were robustly built – you could drive the hell out of their power amps into the most difficult loads without issue. Back when I had a pair of Apogees, Krell amps were the only amplifiers that would power these legendary ribbons without self destructing.

Fast forward to 2018. Krell had been languishing somewhat for the last decade, but now with Walter Schofield in charge of things, and some new product updates from the engineering department, they are again highly competitive. Best of all, that Krell magic is back. For some time, Krell amplification had taken on a bit of a forward, hyperdetailed sound. The new XD amplifiers have returned to more of that slight bit of warmth and tonal saturation, combined with a level of bass slam that made Krell famous. I’ll stick my neck out here and guess that this is a sound that more true music lovers might enjoy, and I’d put the tonality of the current XD amplifier more in the same ballpark as the other solid-state, Class-A amplifiers I truly love: vintage Krell, vintage Levinson, Pass, and Luxman. More of that kind of sound.

Which brings it all full circle, because Schofield used to work for Levinson, so he brings a lot of expertise to bear on carving out today’s Krell, and their place in the market. Krell was serving up great sound at the recent Rocky Mountain Audio Fest, showing off the new XD amplifiers, but even more exciting is that they are offering an upgrade for their past Duo amplifiers to bring them all up to XD spec at a very reasonable cost. In the case of the Duo 175, only $1,000. My inner tree hugging personality loves this, because you don’t have to abandon your old gear to step up to the latest/greatest. Audio Research has had tremendous luck with this and after hearing the new XD side by side with the older version, I expect Krell to do the same. Just so everyone is clear, this upgrade can be done to the amplifiers currently in the i-Bias lineup: 125/175/300 Duos, the Trio and the 375 and 575 Solo. The new K-300i already includes the XD upgrade in their DNA. The “Chorus” line of amplifiers can also be upgraded.

Fortunately, Schofield made my job easy. He sent me an old version along with the new amp. While it’s great to rely on “sonic memory,” nothing gets the job done like having them both side by side to compare. So using the new D-01 DAC/streamer from Esoteric ($20,000) in for review that I’ve become very familiar with, Nagra’ s Classic preamplifier ($17,000) and a pair of GamuT Zodiac speakers ($149,000/pair), all cabled up with Cardas Clear cable, the comparison was a relatively easy task.

Taking this a bit further, I borrowed a good friend’s first gen KSA-50 for a true comparison. Ken Kessler wrote enthusiastically about the KSA-50 for TONE here (http://www.tonepublications.com/old-school/krell-ksa-50-amplifier/) so of course, I had to purchase one to take that trip down memory lane. But like Pokemon, you can’t catch them all, so when the review was done, it went to someone close. Which means loan privileges, of course! So now we had the last version, the new version and a great original to compare.

Initially, there’s no comparison between the two current models – the jump in resolution and musicality is massive. It’s like they are channeling the sound that made Krell famous, while incorporating the changes in technology that have come to be over the last 35 years.

The raw emotion that generated so much excitement over this brand in the 80s is back in spades, yet without losing that magic, there is more low level detail, and more refinement. This is a tough combination to master, yet Krell has. It’s like taking a car with a great paint job, wet sanding it with 2500 grit sandpaper and then buffing to a higher luster than you thought possible – yet there you are.

We’ll have a full review of the Duo 175XD before the end of this year, but for now, consider this more of a comparison between new and old versions to let you know what’s new. Anyone thinking about doing the upgrade, the answer is an unqualified yes – this is the best thousand bucks you will ever spend in high end audio, and this upgrade applies to all their stereo and multichannel power amplifiers. The three channel amp, the five channel, seven channel and the monoblocks. As with past Krell upgrades, the owner is responsible for shipping in both directions. Schofield says that current upgrades are “dependent on production volume,” so it’s best to call service/support and find out what the backlog is.

The folks at Krell are calling this “The New Sound of Krell,” but I submit that they’ve just returned to what made them great in the first place, bringing it up to date with the best advances in audio technology that have come our way in the last few decades. I’d say they’ve found their way back home.

Krell returns to form with an exceptionally capable amplifier for well-heeled home theaters where quality takes precedence over quantity.
Michael Trei - Feb 13, 2019

"After a few years spent flying under the radar, Krell is very much back in business. While the company's main focus has always been two-channel audio, the Theater 7 shows that it's also a serious player in the multichannel game. For a home theater where the main focus is quality rather than trying to blow out everyone's ears, it's hard to beat Krell's Theater 7 amplifier.

AT A GLANCE
PLUS
5 STAR Perfomance
Class-A sound with improved efficiency
Exceptional transparency and control
MINUS
Not the most powerful amp on the block
Display may be unnecessary for most users
THE VERDICT
Krell returns to form with an exceptionally capable amplifier for well-heeled home theaters where quality takes precedence over quantity.

"It's hard to overstate the importance of Krell Industries in the history of high-end audio. Founded by Dan and Rondi D'Agostino in 1980, Krell was the audio equivalent of Lamborghini—an audacious riposte to more Ferrari-like rivals such as Mark Levinson and Audio Research. For almost three decades, Krell went from strength to strength, introducing a stream of ever more ambitious products that tested the depth of their customers' pockets, along with the strength of their audio equipment shelving. Then, starting around a decade ago, the brand slowly slipped off the radar screens of most audiophiles.
 
We now know that the D'Agostinos were the target of what Dan has described as a hostile take- over by a group of investors. The new owners were more interested in making a deal to put Krell-branded high-end sound systems in Acura cars than in pursuing the comparatively small home audio market. Before long, some products were being manufactured in China, and Krell's edge slipped away.
 
While Dan moved on with a new venture, Rondi stayed and fought for the company she had co-founded 30 years earlier, eventually succeeding in regaining control. Krell is now working to reestablish its brand as a world leader in a somewhat smaller, yet even more competitive, high-end audio market. The Theater 7 amplifier is part of that process.
 
Krell amplifiers have always been overstated in design and understated in their on-paper specifications. Back in the 1980s, we would talk about “Krell watts,” where the amp's massive power supply and conservative on-paper power rating meant that it could drive speakers in real world systems way beyond what the numbers would suggest. With 7 x 105 watts, all channels driven into 8 ohms, the Theater 7 may not sound like a powerhouse, but with most speakers it can really deliver the goods.
 
Krell built its reputation on amps that deliver pure class-A power, free from the switching distortion common to more typical class-A/B designs. The problem is that pure class-A amps are notoriously inefficient and pump out huge quantities of heat. Instead of having to make a choice between ultimate sound quality and efficiency, Krell developed what they call iBias Class A to give you both at the same time. While sliding bias amps are nothing new, the difference with iBias is that the bias level is determined by what's happening at the amp's output where the speaker load is connected, rather than at the input.
 
Setup
Despite being the smallest and most affordable multichannel amplifier in Krell's lineup, the Theater 7 ($7,500) is still a beast by any normal standards. Weighing in at 70 pounds and measuring over 20 inches deep, you're going to need a pretty stout shelf to support it. A bottom-mounted cooling fan ensures that things never get too hot, but Krell still advises that you give the amp plenty of breathing room.
 
As with any power amp, hookup is straightforward. Each of the seven channels has both balanced XLR and single-ended RCA inputs, but rather than putting a switch in the signal path to select between them, Krell includes seven little copper loops that short the inverted phase of the XLR input to ground when it's not being used. Krell describes the speaker terminals as five-way binding posts, but I found they weren't particularly well-suited to larger spade terminals, working best with either bare wire or banana plugs. The power inlet uses a hefty 20-amp capable C20 IEC plug rather than the more common 15-amp C14 variety, although the supplied power cable has a standard 15-amp plug at the wall outlet end for compatibility. Rounding out the connections are a 12-volt trigger input and a LAN port.
 
While the Theater 7 doesn't have its own control app, it can be addressed remotely via the hardwired LAN connection. When you switch on the amp, the front panel display shows an IP address, and when you enter that IP address on a portable device or computer that's on the same network, a control screen pops up. From there you can update the firmware, switch the amp on or off, adjust the no-signal switch-off timer, monitor the operating temperature and fan status, and carry out other operations. However, this functionality is meant more for a custom installation professional or Krell technical support to diagnose problems remotely than it is for user operation.
 
I primarily used the Theater 7 to drive my PSB Synchrony seven-channel surround speaker rig, but rather than using them with my subwoofer as I would normally do, I simply ran the Synchrony One towers full-range and switched off the sub. This allowed me to evaluate the amp's full-range performance without siphoning off the deep bass frequencies to a separately powered unit.
 
Performance
Starting with two-channel music streamed from Qobuz, I fired up some of my favorite evaluation tracks. It immediately became clear that despite its name, the Theater 7 isn't just for movies. Drumming legend Steve Jordan is famous for the crisp snap that he gets from his snare, and on the reggae track “Words of Wonder” from Keith Richards' Main Offender album the impact and dynamics of his stick work was certainly ear-opening. Charley Drayton's bass on this track is a great test of an amp's ability to control a speaker. With the Theater 7, his bass lines were full-bodied and powerful, yet also tuneful and easy to follow.
 
Any home theater amp should be expected to deliver sledgehammer dynamics and an ability to maintain an iron grip on the speaker drivers, but it can be a taller order to combine that with subtlety and transparency. The track “Ramblin' Boy” from The Weavers' Reunion At Carnegie Hall is a tough test of those properties. When I listened to it with the Theater 7, the purity of Pete Seeger's voice, and the huge sense of natural spaciousness when the crowd joined him in singing, provided an impressive demonstration of the benefits of the Krell's iBias Class A circuitry.
 
While Incredibles 2 didn't have quite the spark that made the original movie so great, there's no denying that the opening nine-minute sequence when The Underminer robs a bank in Metroville is a fantastic home theater demonstration. With the combined sounds of the Underminer's tunneling machine and money vacuum, the Incredibles' attempts to stop him, and a jazzy music background all going at once, this sequence can give any audio system a real workout. The Theater 7 maintained its composure throughout the clip, with dialogue remaining clear and fully resolved. Even without benefit of a subwoofer, the combination of the Krell amp and the Synchrony One tower speakers managed to get the walls shaking in my 14 x 16-foot theater room.
 
After taking into consideration “Krell watts” versus what you get with more typical power amps, 105 watts-per-channel can still be a limiting factor in some larger rooms, especially when inefficient speakers are used. Personally, I'm more of a quality over quantity kind of guy, and I'd always go for an amp like the Theater 7 over a lesser alternative with a higher power output specification. In my setup, I never felt like I was running short of juice. (Of course, if you want to have it all, Krell also offers the 7 x 200-watt Chorus 7200XD amplifier.)
 
Conclusion
After a few years spent flying under the radar, Krell is very much back in business. While the company's main focus has always been two-channel audio, the Theater 7 shows that it's also a serious player in the multichannel game. For a home theater where the main focus is quality rather than trying to blow out everyone's ears, it's hard to beat Krell's Theater 7 amplifier."
 
All I can say is WOW! I have never, and I repeat never, in over 30 years of professional audio sales and system design, heard a solid state product like this before.
Dave Lalin, - Audio Doctor

SUMMARY: All I can say is WOW! I have never, and I repeat never, in over 30 years of professional audio sales and system design, heard a solid state product like this before. 
The phrase "tube like" has been bandied about for years when you have a solid state product that strives to recreate some of the magic of modern tube electronics, however, with the new K-300i, which I understand was the inspiration for the XD upgraded Duo, Chorus and Solo amplifiers series, you have actually done it!
There is an organic wholeness and lack of grain to the sound which once you experience it, you know in an instant, this is not your typical solid state Hifi gear.

I am writing this email to you while listening to our brand new demo KRELL demo K-300i Integradted amp playing Miles Davis, Herbie Hancock and Lee Morgan tracks.

All I can say is WOW! I have never, and I repeat never, in over 30 years of professional audio sales and system design, heard a solid state product like this before.

The phrase "tube like" has been bandied about for years when you have a solid state product that strives to recreate some of the magic of modern tube electronics, however, with the new K-300i, which I understand was the inspiration for the XD upgraded Duo, Chorus and Solo amplifiers series, you have actually done it!

There is an organic wholeness and lack of grain to the sound which once you experience it, you know in an instant, this is not your typical solid state Hifi gear.

The sound of the K-300i just draws you in to the experience of music. Even listening from the next room, the piano and organ have the flowing roundness of a real instrument.

Another extraordinary trait of this little amplifier, pun intended, it weighs 52lbs and feels like it was cut from a solid block of metal. There was a rim shot on the drums which made me lift my head from reading emails while sitting in my listening room. It was so life like and startling, and this is with only a short period of break in.

Combine this magical liquidity and sense of presence with a deep, well controlled bass response, a large soundstage, good top end extension, and thrilling dynamics, and add in a modern feature set with Roon and MQA capability, built in ethernet streaming, Apt X Bluetooth, HDMI in and outputs, and a ton of both analog and digital inputs, with enough power to drive real world loudspeakers, and it makes this one very special integrated amplifier. I will find it hard to recommend anything else but Krell to my clients, and we sell many of the top performing brands of electronics in all of audio.

We have not yet fired up the big guns, our new Demo Duo-300XD & Illusion-2 [reamp/DAC. I expect we will find this gear is even better than the little integrated with the XD upgrades as I’ve read in many publications over the past few months, and again we will likely find it hard to recommend our more expensive reference gear which is well over $50k. This level of sound quality is more akin to radically more expensive brands. Please get the word out that Krell is back! We are so pleased with these new products, you are going to have a bright future.

Krell is one of the foremost gems in the vein of classic American high end manufacturing, and like Harley Davidson, you are well on your way to restoring Krell back to its glory days.

I have owned many classic Krell products like the KSA 250s, a KRC HR, and 450 Mcx Mono blocks, as well as some of the finest tube gear from Conrad Johnson and VAC, so I know what good sound sounds like. The new K-300i is a quantum leap over the older classic Krell gear, and anyone who doubts that just needs to listen for 30 seconds to confirm that.  

Dave Goodman should be congratulated. Whatever he figured out with the XD series circuit advances the art of music reproduction.

Thank you for your recommendation of the K-300i and Krell in general, I can't remember the last time a product in this price point sounded so remarkable and was such a joy to use.

Please feel free to quote me on this, I stand by absolutely every word.

Sincerely,
Dave Lalin - Audio Doctor
The Krell K-300i - The Return of a Classic
Gregory Petan

SUMARY: "It’s a true treat for this long time Krell user to hear what they’ve achieved with their latest XD technology and the K-300i in particular. At this price, it can make an excellent anchor for a reasonably priced, yet high performance audio system. Its compact form factor makes it an easy roommate to live with as well. “ … "The K-300i is a piece that I suspect its owners will treasure for a long time.

 
It’s funny what you remember. My tenure with Krell goes way back, to the demo room I was scared to enter, where an early Krell KSA 150 was matched to a pair of Apogee Stage speakers. Even though I had just purchased a Rotel integrated from the same dealer the “Krell room” seemed like exalted territory.
 
The sound and appearance this combination made played heavily on my senses – even the smell of this amplifier had an aroma that neither the Classe or Levinson amplifiers possessed, and this combination that was the KSA 150 engaged on all levels. It was an audiophile elixir. I soon became obsessed with Krell and purchased a KSA 150.
 
Moving up the product range, the next generation FPB 300, FPB600, KSL preamp, SPB32-X DAC, KRC preamp, the KPS20i cd player and finally the KPS25i cd player would follow. This was money spent with consumer dollars, not reviewer dollars.
 
Throughout my journey reviewing a wide range of manufacturer’s components, I’ve always rooted for Krell’s success, though I haven’t had much experience with current products since founder Dan D’Agostino moved on to form his own company. In the middle of evaluating a number of integrated amplifiers, Krell’s Walter Schofield offered the first crack at Krell’s K-300i, making for an excellent opportunity to revisit the brand.
 
Slim and powerful
 
Despite a low-profile enclosure, the K-300i weighs in at 52 pounds. Producing 150 watts per channel into 8 ohms, doubling into 4, the K-300i provides the weighty, grip that will entice newcomers, and be familiar to fans. The 1/2-inch milled aluminum front panel (available in silver or black) completes the homage to Krell products past, while the curved front keeps an eye on the future.
 
The K-300i is loaded. Equipped with 2 HDMI inputs, 1 HDMI out and a preamp output to compliment two pairs of balanced XLR inputs and 3 RCA line level inputs, everything at your disposal will easily plug in. Those checking the digital box also have Toslink and coax inputs along with USB and RJ45 ethernet inputs, as well as Bluetooth/aptX capability. This is a well thought out product as a stand-alone control center or integrated into a full home system via the RS-232 ports.
 
Vinyl lovers will need an outboard phono stage, but with so much going on in this compact chassis, I’d almost prefer keeping the delicate analog signal out of this box, and why pay for functionality you don’t need? Digital music lovers are in luck, with Krell offering an internal, streaming DAC for an . This includes an on-board DAC and Roon Ready streamer, that will decode digital files up to 24/192 and unfold MQA as well.
 
Krell’s David Goodman, their director of product development and head of engineering is the person behind the current XD series of amplifiers. As we saw in a recent comparison, the difference between their last series of amplifiers and those with XD technology, the improvement is not subtle.
 
Goodman relates that the XD upgrade (Xtended Dynamics, Xtended Dimensionality, Xtended Detail) “takes an already great sounding amplifier, and raises its performance to the next level. This is a perfect example of Krell’s continuous R&D efforts delivering benefits across multiple product lines. During the development of the K-300i, we discovered substantial sonic improvements lowering the amplifiers output impedance below traditional norms. Applying this to the existing products made for an equally big improvement and required a unique designation, hence XD. This lower output impedance exerts more control over the speaker drivers and damps out unwanted vibrational modes, allowing a more accurate reproduction of the original signal.”
 
Exceeding expectation
 
Fully anticipating big dynamics and a tonal balance favoring the lowest octaves, as with past Krell product, the K-300i is vastly different from past Krell efforts. It’s a top to bottom improvement towards a more refined, yet more musical sound. The lower registers are more refined and controlled at the same time.
 
Retaining the dynamics and forceful low end that’s made Krell famous with audiophiles the world over, the K-300i is more nuanced and natural in its musical delivery. There is a sweetness to the sound that is reminiscent of the original KSA-50. The K-300i is non-fatiguing, inviting you to turn up the volume on your favorite tracks – right out of the box. That’s always a great sign. Remember, Krell amplifiers are still class-A, but thanks to Krell’s current i-Bias topology, they don’t run as hot, or draw as much power at low volume levels as the original models did. Yet the K-300i still draws 900 watts from the AC line at full output – and generates a fair amount of heat.
 
Utilizing a wide range of speakers from Sunny Cable, Lansche and PBN, nothing threw the Krell a curve ball it could not field. After a solid week of burn in, some direct comparisons to my reference D’Agostino Momentum Preamplifier and Pass Labs XA200.5 monoblocks, reveals the big bucks gear still having the edge, but it’s not as big as you might think. The key word here is value. This is performance that would have been unheard of ten years ago for this price.
 
Great with all sources
 
This newfound balance altered my approach. Past Krell components always had me reaching for the more bombastic selections in my music collection, but the K-300i sends me to vocal rich recordings, exploring the heart of the mid band and treble in ways that older Krell designs did not inspire as a first move. From Sarah Vaughn’s previously unreleased concert pressed by Devialet, via my VPI Avenger Reference, with the Gryphon Sonett and Boulder 508 phono stages, it’s easy to see what this amplifier does so well.
 
Liquidity, color, expressive dynamics, and space. All positive aspects of these two phono stages, and the differences between them are clearly rendered by the K-300i, revealing the emotion present in the recordings auditioned. Sarah Vaughn’s vocals sound full of life at times and a weary at others. Eva Cassidy’s Live at Blues Alley is another familiar go-to when trying to reproduce inflection, a wide range of dynamic control, and emotional impact. “Bridge Over Troubled Water” from this band is wonderful, and though I’ve heard this recording so many times, the Krell never gets in the way of the music.
 
Compared to my reference McIntosh MB50 streamer, the Krell provides a more intense presentation to the Mac’s slightly sweeter rendition. If I didn’t already have an outboard streamer, I could happily live with the one built into the Krell. For the less than the price of a decent pair of signal cables and a power cord, you can have it all inside the chassis. A great thing for those craving simplicity.
 
Just a quick note about the HDMI performance of the K-300i. In a word, it is phenomenal. Watching Mary Queen of Scots, my wife and our friend agreed, it was like we had upgraded our modest Epson projector several levels. Color saturation and detail rendition was startling as was the contrast and brightness. If you are like me and your audio system does double duty as your home theater, the upgrade in video quality alone not to mention the ease of integration is worth at least half the overall cost the K-300i.
 
Coming to grips with it all
 
On balance, this is one of the best sounding pieces of Krell gear I’ve had the pleasure to use. While the last bit of resolution and slam from their top products is not here, because you can’t have everything for only NZ$15,995, Krell has made it a point to deliver a high degree of sonic excellence and balance in this compact package. Those needing more power can consider using the K-300i as a control center and adding a more massive Krell DUO or MONO power amplifier later.
 
The only part of the K-300i that I didn’t terribly enjoy was the Bluetooth streaming, but this is not my favorite way to listen anyway. Still, it is nice of Krell to offer this, so that when friends drop by and want to share their favorite playlist, connectivity is only a click away.
 
It’s a true treat for this long time Krell user to hear what they’ve achieved with their latest XD technology and the K-300i in particular. At this price, it can make an excellent anchor for a reasonably priced, yet high performance audio system. Its compact form factor makes it an easy roommate to live with as well.
 
And I still think about that KPS25i – it was one of the coolest pieces of audio gear I’ve ever owned. It’s funny what you remember. The K-300i is a piece that I suspect its owners will treasure for a long time.
The sound with the K-300i driving the Sonus Faber Olympica III Loudspeakers was exceptionally fast and clean—more clear mountain stream than, what, furry animal babies?
Jim Austin,

Is the K-300i's sound consistent with the company's new more approachable image? Is it, as the brochure suggests, "clean, powerful, natural sound in all its subtleties, colours, and gradations"? It's impossible to judge based on a short listen in an unfamiliar room and system with unfamiliar tunes, but here's my first impression. The sound with the K-300i driving the Sonus Faber Olympica III Loudspeakers was exceptionally fast and clean—more clear mountain stream than, what, furry animal babies? I don't know these loudspeakers, but I've found the Sonus Faber house sound to favour warmth and ease over speed and ultimate resolution. Driven by the K-300i, the Olympicas didn't lack for warmth—nor were they the least bit bright or etched. But there was no dearth of articulation, from the bass on up. So, yes, waterfalls and Alpine pools, bracing, cool, clear water—those aren't bad sensory analogies.

Krell had a big display at Munich High End show and seems to be on the brink—or maybe in the midst—of a major new-product and marketing surge.

Walter Schofield, the company's COO, told me that in addition to a few new products recently introduced, many more are just on the horizon. The new products—and the new marketing push—are based on two recent technical advances. The first, iBias, which was introduced by Krell in 2014, is a sliding-bias scheme that ensures there's always a positive bias for both phases of the waveform. Sliding bias is like class-A in that a bias voltage is always maintained, eliminating crossover distortion, but instead of a large, constant bias as in class-A, the bias voltage tracks the signal, staying as small as it can be while assuring that it's bigger than the signal. In contrast to most (or all? I don't know) other sliding-bias approaches, iBias uses the amplifier's output —not its input—as its reference, so it accounts for the interaction between the amplifier and the loudspeaker.

Longtime Krell designer David Goodman told me that the resulting distortion is almost entirely of the third-harmonic variety; he insisted that third-harmonic distortion is preferable to second-order—which provides some indication of the sound Krell is aiming for.

The second advance, which the company calls XD, is a method for reducing output impedance. The key insight, which Goodman told me was discovered in the course of developing the K-300i integrated amplifier is that "lowering the output impedance below traditional norms" results in "substantial sonic improvements."

Krell's technology surge comes with a renewed marketing effort aimed at altering the brand's image. On the substance side there's a renewed emphasis on product reliability and customer support: The K-300i brochure notes the company's commitment to "ultimate reliability" and "white glove service," and the 300i comes with a minimum 5-year warranty. On the image side, there's a focus on nature and humanity. That brochure offsets images and descriptions of the product and its sound with nature photos and an endorsement of the Nature Conservancy.

The energy savings facilitated by iBias fits this environmental image—but many audiophiles will likely be more influenced by the practical advantages of the technology than the planet-saving ones. The K-300i can deliver 150W into 8 ohms and double that into 4 ohms, according to published specifications. A pure class-A amplifier capable of that much power would be big and heavy and dump a lot of heat into the listening room. The K-300i is a normal-sized component—a typical 17 1/4" wide and 18" deep and a few inches tall—and it weights a modest 52lb. It burns just 46W at idle; a 150W class-A amplifier would consume more than ten times that much power and put more than ten times as much heat into the room.

Is the K-300i's sound consistent with the company's new more approachable image? Is it, as the brochure suggests, "clean, powerful, natural sound in all its subtleties, colours, and gradations"? It's impossible to judge based on a short listen in an unfamiliar room and system with unfamiliar tunes, but here's my first impression. The sound with the K-300i driving the Sonus Faber Olympica III Loudspeakers was exceptionally fast and clean—more clear mountain stream than, what, furry animal babies? I don't know these loudspeakers, but I've found the Sonus Faber house sound to favour warmth and ease over speed and ultimate resolution. Driven by the K-300i, the Olympicas didn't lack for warmth—nor were they the least bit bright or etched. But there was no dearth of articulation, from the bass on up. So, yes, waterfalls and Alpine pools, bracing, cool, clear water—those aren't bad sensory analogies. As for the subtleties, colours, and gradations, judgment on that will need to await a longer, more focused listen.

A streaming DAC module is available, the DAC supports Roon, Tidal, Qobuz, Spotify, and MQA. The K-300i's warranty is 5 years from the purchase date, or six years from the time it was sent out from the factory, whichever is longer.

KRELL IS BACK ON THE MAP WITH NEW K300I-XD INTEGRATED AMPLIFIER - Welcome back, Krell!
Marc Rushton

Further revisions and developments have also been realised. David Goodman, Director of Product Development at Krell since 1987, said:

We discovered that with modifications to the output stage, we could vastly improve sound quality, across the board, to all of our amplifiers.

The result is a deeper, darker, blacker background that provided significantly better macro and micro dynamics, more silence between the notes. Vocals and midrange took on an organic, yet more vibrant tone, enabling us to hear much more body, and even though our amps were great before, there was a very significant improvement.

Welcome back, Krell!

KRELL IS BACK ON THE MAP WITH NEW K300I-XD INTEGRATED AMPLIFIER
KRELL IS BACK ON THE MAP WITH NEW K300I-XD INTEGRATED AMPLIFIER

Finally, there's some good news coming out of Connecticut's Krell headquarters. Discerning audiophiles have embraced the iconic US brand in the world of high-end Hi-Fi since 1980 when Dan and wife, Rondi D'Agostino founded the company.

Since those early days, it's endured changes of ownership and direction, while Dan D'Agostino moved on leaving ex-wife Rondi at the helm.

More recently, a series of unfortunate events and circumstances may have created some doubt as to Krell's future, but we are now being reassured that Krell is back!

Industry veteran, Walter Schofield has joined the company as Chief Operating Officer (COO). Across his career, Schofield has worked for SVS, Meridian, Linn, Mark Levinson, and more recently, Emotiva in the role of Vice President of Global Strategy.

Schofield told StereoNET:

We have a busy season ahead of us, but our most important job is to ensure that every product bearing the Krell logo is unquestionably reliable and delivers ultimate performance, now, and for years to come. It’s our main, laser-like focus, and our commitment to our dealers and customers.

Schofield has been quick to communicate with dealers and distributors around the world, acknowledging the mistakes made in the past, but also promising that the future is positive for the Krell brand. The message from Krell is that its business as usual, and “they will be silent no more”. Very encouraging!

And to back up those claims, Krell has announced a brand new product that is expected to become available in Australia in early 2019.

The Krell K300i-XD is a 150w Class A Integrated Amplifier with DAC and streamer, packed with features and connectivity options.

Boasting a 770VA Transformer and 80,000 uF capacitance, Krell's Current Mode topology is used with fully differential circuitry that it says runs from the input stage through to the last output gain stage. This, according to Krell, “provides extremely linear and extended frequency response curve with smooth, effortless highs and extremely dynamic bass energy.”

Available in two configurations, the 'Classic' and the 'Digital',  the latter version includes an ESS Sabre Pro DAC and network streaming audio renderer supporting all major file formats and up to 192kHz/24bit resolution from UPnP servers and NAS devices.

Latest trends have not been overlooked with the XD Digital version also compatible with MQA and Roon Ready, along with provision for popular streaming platforms including Spotify, Tidal, Deezer, Qobuz and vTuner Radio.

Krell has also realised the importance of HDMI in most user's applications today and has delivered with HDMI 2.0 inputs and outputs, supporting 4K UHD and HDR to allow for integration into Home Cinema systems.  

A single USB port is available on the front panel with other USB ports on the rear, and there's also a Bluetooth aptX Receiver for streaming from your smartphone or tablet, while an internal web server offers a remote graphical user interface for control.

The K300i-XD features two pairs of balanced XLR inputs and three pairs of RCA inputs, digital inputs comprising coax, EIAJ optical, 2 x HDMI, and USB inputs.

StereoNET first wrote about the upcoming Krell K300i back in July this year. Since then, the reported price has increased not insignificantly. However, this reflects the company's renewed direction and commitment to quality and the ongoing Krell legacy. 

The initial K300i prototypes utilised Chinese sourced mainboards, whereas, under Schofield's direction the new release now uses only US factory sourced mainboards, a decision he says was a necessary move.

Further revisions and developments have also been realised. David Goodman, Director of Product Development at Krell since 1987, said:

We discovered that with modifications to the output stage, we could vastly improve sound quality, across the board, to all of our amplifiers.

The result is a deeper, darker, blacker background that provided significantly better macro and micro dynamics, more silence between the notes. Vocals and midrange took on an organic, yet more vibrant tone, enabling us to hear much more body, and even though our amps were great before, there was a very significant improvement.

Welcome back, Krell!

Truly Impress The Most Demanding Audiophile!
McEvoy

With KRELL’S NEW XD upgraded to their I-Bias amplifiers comes a new level of demand & respect from audiophiles everywhere while we believe Krell sounded great before, the XD upgrades continue to astound listeners with the major sonic improvements. The “XD” upgrade for the Chorus/Duo/Solo amplifiers reduces the output impedance to less than half of its original value. This lower output impedance better damps unwanted speaker vibrational modes. Changing the output impedance also necessitated re-compensating each amplifier stage to achieve optimal critically damped transient response. This ensures that the amplifier accurately follows the dynamics of the input signal.

Here’s a Couple of Press Reactions to The Krell Poers System:

“The electronics were supplied by Krell Industries and Rondi D’Agostino, Managing Director, and Walter Schofield (COO) were on hand to explain their Krell products. The Posh speakers were driven by a Krell Duo 300 XD amp and Krell Illusion preamp with an Oracle Delphi Signature turntable and Oracle PH-200 phono stage as the source. The Grand Studio speakers were fed by an Oracle Origin turntable, an Oracle Origin tonearm, an Oracle PH-100 phono stage, and a Krell K-300i amplifier. All cables were by Kimber Cable.

If there were one word I could use to describe the sound in this room from both speaker models, it would be ‘fun’. The expression on the faces of the audience said it all. It was very obvious that everyone in the room was having a great time. We waited for 10 minutes to get a good seat but it was in vain. The people in the room were having too much of a good time to give up their seats. We were therefore forced to listen by standing at the back of the room. Despite this, we could easily tell that the sound quality was quite outstanding. The PRaT (pace, rhythm and timing) was spot on, the highs and the mids were very seductive and the bass was taut and well controlled.”– Part Time Audiophile

“Oracle, Krell and Gershman Acoustics have joined forces to offer a flawless presentation around two systems at very different price levels. The most ambitious of the two systems consisted of an Oracle Delphi Signature turntable, an Oracle PH-200 phono stage, a Krell Illusion Preamplifier, a Krell Duo 300 XD amplifier and the famous Gershman Acoustics Posh loudspeakers. It is a very ambitious audio system with immense qualities in terms of sound.

However, what really caught my attention is the second audio system whose proposition is geared towards a much more affordable budget. It consists of an Oracle Origin turntable, an Oracle Origin swivel arm, an Ortofon MC-1 Turbo cell, an Oracle PH-100 phono stage, an integrated Krell K-300i amplifier and Gershman Acoustics Studio 2 loudspeakers. All cables were from Kimber Kables. What a beautiful HiFi system with a very lively swing! First, the Platinum Origin injects a serious dose of life into a system. The surprising Krell K-300i amplifier is rock solid and drives the Gershman Studio 2 with an iron fist. The sound filled the room with a jazz tune with an excellent sense of rhythm and I actually caught my foot accompanying the tempo. Nice demo, we will surely have the opportunity to listen this set-up at the Montreal Audio Show 2019 in March. Don’t miss this !” – TED (Trends, electronics and designs)

“And that segues conveniently into the Gershman Acoustics demonstration room where the lovely Mrs. Gershman showed their fabulous $129,000 Posh flagship as well as the Studio II in a pair of integrated metal stands. Sharing the suite were Krell reps Rondi D’Agostino and Walter Schofield displaying their advanced new Krell K-300i integrated  The priority in this room was music and when the discussion turned not to equipment details but incredible sounding demo material, you knew the hardware had properly done its job. – Six Moons

Suddenly somebody comes around and pulls the veil away and lets you see the paintings in their full glory, every stroke of the brush and every speck of paint. K-300i did that for me for the music. Get it if you can. …
Vedran Simunovic

Conclusion: Yes, it is in the upper price bracket. On the other hand, when will I own a Picasso painting? K-300i is a work of art, and moreover, a work of art that makes you enjoy other works of art in a truly breathtaking way. Imagine if painters made great paintings for centuries but kept them under a veil that only hinted at their true beauty. Suddenly somebody comes around and pulls the veil away and lets you see the paintings in their full glory, every stroke of the brush and every speck of paint. K-300i did that for me for the music. Get it if you can.

REVIEW: You’ve seen it many times in the movies. A prodigal son, or a lone cowboy, or a legendary warrior returns from what was really a self-inflicted exile. A long time ago he was the best, but something happened and he lost his way for a while. Now he’s with us again. Everyone cheers, hats fly into the air and an old friend throws a welcoming arm around his shoulders and in a soft, moving voice says: “Welcome back!” Enter Krell’s new high-tech K-300i integrated amplifier.

Appearance + Features

That was exactly the impression I had after listening to Krell’s K-300i for five minutes and it hasn’t left me since. It was also a reminder that people like me spend so much of their precious time on this planet obsessing over Hi-Fi because it’s a genuine and unique opportunity to personally enjoy real works of art, either through their almost supernatural looks or through “being there”, when everything works properly, speakers disappear and you’re transported into the music venue, wherever and whenever that may be.

The K-300i impresses you right from the start with its commanding presence, especially in the “I’m the boss” black. Gone are the showy features of the days past, now Krell can justly claim that it has really made a work of art. K-300i achieves a unique blend of sturdiness and elegance because it oozes build quality no matter where you look or touch and then combines it with an understated curved front, unobtrusive display and neatly arranged controls. This work of art also has a lot of gravitas. Literally. Many amplifiers may be larger and heavier than K-300i but quite a few contain a lot of empty space for a number of very valid reasons. Not this one. It’s jam-packed with hardware and when you peek through its cooling slots you can’t see many empty spaces at all. When you lift the densely packed amplifier you might even wonder if it really needs to be plugged into the wall at all (“…there must be a nuclear reactor in there somewhere…”).

Krell

Although it’s nominally a Class-A amplifier using Krell’s proprietary ‘iBias’ circuitry, the K-300i dissipates surprisingly little heat for its stated power (150 watts per channel at 8 ohms and 300 watts per channel at 4 ohms). Krell specifies that just about two inches of free space above the amplifier are required to assure proper cooling. I’ve put K-300i to the test on this and it passed with flying colours, which means that you should be fine to install it in places where many other amplifiers of similar power would be out of the question solely because of their ventilation requirements. Neat.

The unit received for review came with a ‘Digital Module’ option, which means that, in addition to the usual analogue inputs, it also had a whole gamut of digital inputs to which you’re able to connect your sources, such as CD/DVD/BR players, streamers, USB keys and whatever the never-sleeping electronics inventors come up with next. Digital inputs include USB, optical, coax S/PDIF, HDMI and the ubiquitous RJ-45 Ethernet port. Of course, in order to decode all this wealth of digital signals, the Digital Module includes an ESS Sabre Pro DAC of impressive specifications. Lastly, the Digital Module has Bluetooth connectivity, which does come in handy sometimes, especially if you’re having a party and/or if you want to play with the frequency response (given Bluetooth’s limitations, although on-board aptX is getting there). All input ports except for one USB are at the back of the amplifier, organised in a tidy logical manner and easy to access and work with. So are the stream of analogue inputs (XLR and RCA) and speaker posts, which accept banana plugs and spades.

Convenience is everything these days. People expect to have their music available to them everywhere and anywhere, anytime while being able to connect any device to any other in two seconds flat. K-300i does not disappoint in this regard. It comes Roon-ready, MQA-capable and with a number of options for many popular streaming services, including Tidal and Spotify, which you can control through the ‘mconnect/mcontrol’ app on your handheld device of choice (Android and iOS versions). This is where I found that K-300i behaves differently to my Oppo BDP-105 player, because the presence of the handheld (phone or tablet) and the running of the app is essential for K-300i’s streaming. For example, if you flick the control app off the screen the streaming stops. If I do the same thing with Oppo’s controlling app, the streaming is not affected at all. However, as long as the handheld is there and so is the app, K-300i’s streaming works just fine. Just remember not to take the phone with you when somebody sends you to check on the front gate during a party…

Krell

K-300i’s network setup is easy and as straightforward as it comes. In my case, everything worked right out of the box with no problems at all. That said, please keep in mind that K-300i has two IP addresses: one for the control app and one for the web interface. When I scanned my network, I found one “Krell K-300i” device on the address 192.168.0.34 and one “Generic” device on the 192.168.0.75 address. When you open the settings of the control app, it shows the address ending with “34”. However, when you check K-300i’s front display, the address it shows is the one that ends with “75”. If you put the latter address into your web browser, you’ll connect to K-300i’s web interface that looks exactly like the front of the amplifier and you can control it just as if you were pressing the buttons on the amp itself. Some might prefer this kind of access, but by the time I discovered it I was already perfectly fine with Krell’s remote control which did everything I needed. At some stage, Krell might find a way to combine the two IP addresses into one, but the current situation of having two addresses is not a problem at all, as long as you know that there are two of them.

K-300i also has a HDMI output, which quite a few devices I encountered use for displaying their interface on a TV, but Krell decided not to include that feature in their current firmware. I hope they will be able to do it at some stage because the small display at the front, although supporting the elegant looks of the amplifier, might require some squinting for people whose eyesight is not 20/20.

I consider all of these as very minor quirks and they did not stop me in enjoying the great sound and great streaming that K-300i was delivering in spades.

Listening Impressions

For quite a while this review was in danger to be a very short one indeed, because in essence all I can say is that K-300i’s command of the sound is absolute. Period! And there is another thing which I never expected to encounter, and somewhere deep down it pains me to admit it, but K-300i sounds better than the power amplifier I designed, assembled, customised and tweaked over the years to suit my Magnepan speakers perfectly, or so I thought.

Now, before you say “…but Magnepans have no bass” or “…but Magnepans have no dynamics”, please let me counter both myths with “Magnepans have to be placed properly”. My listening room is just 4m x 3.7m and has some irregular features, which did present a challenge, but after spending a few weeks moving speakers around (yes, weeks, because panel speakers radiate both front and back and with Magnepans millimetres count) what was achieved has been a veritable acoustic nirvana in which a great recording rewards you with a front seat performance that’s barely distinguishable from the real thing. Bass, mids, highs, dynamics, soundstage, you name it – they’re all first class. Weeks were spent, but that was years ago and I never had to change the position of my speakers again. Sheer bliss!

Enter K-300i, “stage left”, as a distinguished guest who you’re happy to entertain for a while but you’re not sure what to expect from. The trouble begins when you realise that Krell managed to deliver value for your $12,000 and that the sound that’s coming out of K-300i elevates your speakers, especially Magnepans, to another level of existence altogether...

The sound quality I heard is more than just about THD, frequency curves and similar technical stuff. According to the theory, a power amplifier is supposed to perform one deceptively simple function: take a signal from the input and reproduce it faithfully amplified at the output. An integrated amp like K-300i performs two more functions: input selection and volume control. On paper, that’s all there is to it, but hi-fi industry has been living off the details since inception. I don’t care for amplifier topologies, valves versus silicon, passive-versus-active or any fashions and fads abounding the hi-fi world, as long as the produced sound is reproduced faithfully and accurately. In my view, any manufacturer, including Krell, has a legitimate right to claim their fair share of acronyms – and they’re welcome to it – but for me K-300i sweeps all those details aside with its marvellously accurate sound that you can never hear enough of and that you never get tired of.

As far as I could hear, Magnepans really appreciate the power and the high current capability of K-300i, as well as its tight control of speakers. In regards to speaker control, you have to keep in mind that speakers often impose a rather peculiar load on an amplifier because mechanical movements of the membrane and/or cone manifest themselves not only as resistance, inductance and capacitance loads but also as delayed current/voltage sources, all of which complicate the lives of Hi-Fi equipment designers. K-300i performs superbly in this regard, in a way that’s more than just about the damping factor. This is quintessential Quality with capital Q. Recordings that used to sound great suddenly reveal another layer of detail and you get a feeling that the speakers are much more obediently following the amplifier’s signal.

Krell

I’d recommend that you audition K-300i with its Digital Module installed because if you’ve ‘gone streamin’’, that might be all you’ll need in the foreseeable future. It incorporates a top-quality DAC and that it lets you utilise a wide variety of streaming services. For music that is not on your streaming service you will need other sources (CD/DVD/BR/TT/R2R…). For this review, I mostly used Tidal, which I’ve been subscribed to for a while and found to be the best fit for my needs.

I also tried K-300i with Redefy Audio Monitors with results very similar to what I heard with Magnepans. I’m sure that K-300i would have handled many other speakers just as well as these two. If your speakers’ main virtue is accuracy, I’m certain that K-300i will reveal their full potential to you. It definitely did it for me.

I have a fairly standard set of test tracks that I use for evaluating equipment. This set reliably reveals strong and weak points of any device in the chain, but in the case of K-300i it was very hard indeed for me to find anything that would require an improvement to what I heard. Then, I expanded the repertoire and tried more and more tracks, but still could not find any weak points. Well, maybe, if your speakers need only 15-20 watts to fill the room with music, you may want to find them a suitably powered amplifier, perhaps a valve-based one. If, however, your speakers love a bit more power and can use additional current – again, if they’re Magnepans – I’d go straight for the K-300i and never look back.

Please let me elaborate on this point a bit.

The K-300i made it literally uncanny to listen to Anette Askvik’s “Liberty”, from the album of the same name, because it clearly revealed the singer’s articulation sounds: mouth opening, breath taking and every movement of her tongue and lips. I did hear them quite clearly before I plugged K-300i into the chain, but this was something entirely different. Another example would be Osibisa’s “Kolomashie”, album Welcome Home, which somehow acquired another layer of African village sounds, while singing and clapping of the performers gained immediacy that I previously thought was not possible. Come to think of it, try Osibisa’s “Seaside Meditation” as well. (I heard it performed live ages ago and the drum extravaganza in the middle of the song lasted 11 minutes flat! It’s still with me…)

Krell

Next, I tried Yello’s “Takla Makan”, album Touch Yello (Deluxe). As the name of the album suggests, the sound makes you feel that you can almost touch the sands of the Takla Makan desert. Watch for the sound of the didgeridoo about 50 seconds into the recording. It gives you a jolt!

When testing, I always try a wide variety of recordings and then let a device “drift” towards its preferred genre of music. In this case, K-300i remained right in its original “United Nations” position and faithfully amplified whatever it was ordered to. For example, when playing classical recordings such as “Jupiter” from Holst: The Planets by Boston Symphony Orchestra, conductor William Steinberg, the orchestra was there, from double basses all the way to the tiny triangle. You could hear cymbals crashing with the same measure of clarity and mellowness as when you hear them live, with no harsh edges anywhere. The next case in point for me was Schubert’s String Quintet (D956), where K-300i effortlessly confirmed the technical brilliance of the performers and the recording made by the Artemis Quartet (with Truls Mørk; Virgin Classics), versus a much more flowery version recorded by the Melos Quartet with Mstislav Rostropovich for Deutsche Grammophon.

As mentioned before, K-300i will make a great recording reward you with a front seat in the venue. The best example of this for me was VH1 Storytellers live album by Johnny Cash and Willie Nelson, which was recorded with just a few microphones in close proximity to the audience. I even played track 1 “Ghost Riders in the Sky” to some people who are admittedly not very particular to country music, but they were nonetheless captivated by the quality of the sound. They asked me to play it again!

Jazz albums, like Crystal Silence Chick Corea and Gary Burton, and Flood by Herbie Hancock benefited greatly from K-300i’s accuracy and dynamics. Flood in its original form is a relatively hissy recording (have a listen to “Butterfly” for the best example; maybe the tapes were not up to scratch), but K-300i reproduces that hiss without making it a distraction. At the same time, the highs are not compromised at all. Whatever is the trick, it has my vote.

Krell

Lastly, I put on Donald Fagen’s The Nightfly and, to my great pleasure, K-300i (in cooperation with Tidal) revealed that it was MQA (Master Quality Authenticated). This added yet another layer of richness to the sound and made me run out of words to describe the end result. Please listen to The Nightfly but be careful because I’m sure that anyone who hears this recording through the setup I described will immediately feel an overwhelming urge to acquire K-300i and never mind the price. As for myself, I had to perform a desensitisation exercise reminiscent of a scene from Some Like It Hot by repeating to myself: “I’m on a budget. I’m on a budget…” before I parted with this marvellous amplifier, particularly because of its delivery of The Nightfly.

Conclusion

Yes, it is in the upper price bracket. On the other hand, when will I own a Picasso painting? K-300i is a work of art, and moreover, a work of art that makes you enjoy other works of art in a truly breathtaking way. Imagine if painters made great paintings for centuries but kept them under a veil that only hinted at their true beauty. Suddenly somebody comes around and pulls the veil away and lets you see the paintings in their full glory, every stroke of the brush and every speck of paint. K-300i did that for me for the music. Get it if you can.

Vedran Simunovic

the sound of a pair Krell Illusion ll and Krell Duo 175 in the mid range I liked it much more than quite hard and cold sound of some older models of the mid-1990s
Webblack.net — тим хто мешкає в мережі

SUMMARY: In the transition to the classical repertoire Krell is the ability to control the acoustics resulted in an extraordinary transparency, which were presented to the most complex fortissimo. Needless to say, «theFirebird» by Stravinsky, I was again stunned and plunged into the thrill, however small violin compositions of Haydn sounded appropriately heartfelt and beautiful. Despite his heroic strength, set can sound soft and gentle, when needed, with very believable voices. Three-dimensional scene, so appreciated by audiophile, Krell manages to pair perfectly with the amendment, of course, on your speaker system and room. In General, the performance of the admittedly gorgeous.

RATING:
Design: 95
Workmanship: 95
Sound: 95
Function: 95
Total: 95
Conclusion: the Krell Illusion ll and Duo 175 is able to give the owner a lot of strong emotions when listening to music of all genres. A new generation of amplifiers Krell was a success and over time will acquire a legendary status.

REVIEW: The name of the American company Krell has long been synonymous with sound of the highest level. The next generation of music lovers discovering branded equipment, and all as affected the outstanding quality of sound and workmanship. However, recently the company went through a rather difficult stage.

Despite the fact that the first Krell amplifier under the brand saw the light in 1980-m to year, in recent years, the company had to work hard to maintain a high level of confidence in their products, which has already become habitual for her. Suffice it to say that pre-owned Krell amplifiers still enjoy huge success with buyers willing to pay for them a sum in excess of the original price! What happened? This is due, firstly, with the departure of the Krell, the founder and chief developer of the company Dan d’agostino behind the creation of all classical models of the firm. And secondly, with ever-increasing user requirements to functional equipment equipment class High End. Component construction principle of the stereo is still not questioned, however, to meet today, for example, pre-amplifier no DAC, and even the wireless module and the streamer becomes more difficult. How successfully managed a team of Krell with upgrading and maintaining the quality of the sound at the proper level? We will check this with the example of the set consisting of the preamplifier Krell Illusion II stereo power amplifier Krell Duo 175.

For each generation of its technology Krell designers continue to invent new forms. The next iteration of stereo equipment, the company also got his very recognizable, though not too original looking. Silver paste with the lights on the center of the front panel came in mind not all inveterate audiophile, however, one must admit that now equipment company looks much more modern, though not as brutal as the classical model. However, the main changes are connected not with the design of the front panel, and hidden inside.

Krell Duo 175

The main stars of the model range of the American firm has always been the power amps, so with them we will start with the introduction kit. Presented to test the stereo amplifier takes an intermediate position in the hierarchy between the entry-level devices and top-end Solo 375 monoblocks.

Power output is claimed at 175 Watts per channel into 8 Ω, actually, hence the number in the title. As we would expect from a Krell amps, when operating at 4 ohms output power is doubled to 350 Watts. That is, as in the previous models of the firm, output stages work in pure class A? Not really. And here we come to the main innovation introduced in the design in recent years. The company’s engineers came up with a cunning move, allowing you to keep all the advantages of operation of the amplifier in class A, but significantly reduce power consumption and heat. This is achieved through the intelligent circuitry iBias, analyzing in real time the level of the current given to the load, and adjusts accordingly the current of rest. As a result, the transistors continue to always remain open, however, the flowing current varies depending on actual load. I must say that trying to do something similar has already been attempted by other manufacturers, but the implementation suggested changing the quiescent current depending on the input signal, which did not give the desired result, primarily, from the point of view of sound quality. Looking ahead, we can say that the Krell engineers had achieved the seemingly impossible.

Another innovative feature is the presence on the back of the RJ45 port. It allows you to manage and control the many parameters of the amplifier via a network interface. Of course, this requires you to connect the device to your home network, where he will be assigned its own iP address. In addition, if you encounter any problems the company will be able to remotely read the code errors and make recommendations for its elimination. Frankly, this feature is unlikely to be commonly used by normal users, however, the mere fact of its existence says about the company’s commitment to meet the requirements of the digital era.

On the rear panel are one pair of speaker terminals and the RCA and XLR connectors for balanced and conventional connections. What is less familiar is the presence of four fans for forced cooling of the output transistors. Previously, the company relied solely on the massive passive radiators. However, thanks to the innovative control scheme, the current peace, to intervene in the case, the fans have rarely. In the rest of the Duo 175 is a classic two-channel amplifier Krell, powerful and imposing.

Krell Illusion ll

The second component of the kit — Krell Illusion II, the younger of the two available in the product line of the company pre-amplifiers. Often when first turned on modern audio equipment with a digital filling the user has to spend some time to understand all the settings and assigning inputs. In the case of Krell Illusion ll I listen to ten seconds after activation.

The front panel contains the activation keys for each of the inputs, adjust the volume level and channel balance, as well as navigate through a short menu. The included remote control is traditionally enclosed in a housing of machined aluminium and is covered with small buttons. The digital part of the pre-amplifier is built on the ESS Sabre chip and is able to work with LPCM signal with parameters 24 bit/ 192 kHz. In General, the apparatus is easy to handle and intuitive.

Sound

Audition set it was decided to hold in a pair of Studio monitors, the legendary JBL 4345. Despite the fact that they have high sensitivity, their 18-inch basewiki still need good control. And horn mid-range section will allow you to easily identify any flaws in the amplifier part proper transmission of voices and live instruments. As the source was the CD player Bryston BCD-1 and the turntable in the VPI Classic. Switching between pre-amplifier and power amplifier were carried out in symmetric and asymmetric Protocol. In the end, there was a preference for the balanced option.

Amplifiers Krell has long earned the reputation of «kings of bass», and I don’t deny myself the pleasure to start the program listening several albums with excellent written bass parties. Well, the reputation has been brilliantly confirmed. For example, the title track of the album Pat Travers «Crash and Burn» sounded so powerful and even frightening that after graduation I had to take a short break to reconfigure the perception of less aggressive genres. If we go back to work a couple of amps on the bass, it is quite obviously the following to improve the sound quality in this range is possible only by acquiring top-end kit from Krell, and that — not the fact that the result will definitely justify the difference in price. All proposed system of records, including Metallica, classic albums Rush, cut by the legendary Bob Ludwig, and challenging enough to play Them Crooked Vultures, was played out almost perfectly. Amplifiers effortlessly disassembled into components and re-assembled in a single unit loud drums and bass guitars and hi-hat don’t forget to sparkle with silver.

In the transition to the classical repertoire Krell is the ability to control the acoustics resulted in an extraordinary transparency, which were presented to the most complex fortissimo. Needless to say, «the Firebird» by Stravinsky, I was again stunned and plunged into the thrill, however small violin compositions of Haydn sounded appropriately heartfelt and beautiful. Despite his heroic strength, set can sound soft and gentle, when needed, with very believable voices. Three-dimensional scene, so appreciated by audiophile, Krell manages to pair perfectly with the amendment, of course, on your speaker system and room. In General, the performance of the admittedly gorgeous.

Since I have had a chance to listen to the work of JBL 4345 monitors paired with earlier generations of Krell amps, it was difficult to refrain from carrying out direct Parallels. In my opinion, the difference in sound with the new model number appears no more than between all of the previous generations, designed by Dan d’agostino. That is to say that the use of iBias has led to the loss of signature handwriting is impossible. Moreover, the sound of a pair Krell Illusion ll and Krell Duo 175 in the mid range I liked it much more than quite hard and cold sound of some older models of the mid-1990s — beginning of 2000-ies. Well, about the bass has been said enough.

The American "delivers". the bottom line is not so much aimed at beautiful, soft, or warm listeners as at listeners who above all appreciate an uncoloured, straight sound.
Jorg Dames

The Krell Vanguard Universal DAC is characterized by:

  • a neutral, no-frills adjustment that could also serve as a standard for other devices.
  • a real “full-range sound building” that effortlessly builds up from the deep bass cellar to the top frequency floors.
  • high dynamics - whether rough bass impulses or fine transients, the Vanguard Universal DAC is one of the most agile components I know.
  • factually balanced mids and honestly accurate highs without undue hardship or sharpening, but also without extra charm. Even if I have little idea of ​​cars: The Krell offers the chassis tuning of a sports car that is permeable to uneven roads, rather than a pleasant limousine feeling.
  • a high resolution, also the spatial differentiation / location accuracy meets the highest demands. The dimensioning of the stage is based on what the music template gives.
  • unexcited, "tool-like" design and robust, professional, studio-like processing. Only the incomprehensibly small volume indicator on the display reduces the practical suitability. Some listeners may also miss a USB-B input.

REVIEW: Classically traditional high-end brands with a special nimbus - Krell certainly belongs to this exclusive circle: Founded almost 40 years ago by Dan and Rondi D'Agostino and finally taken over by a group of investors, the Americans have an eventful vita - especially with The construction of weighty amplifiers gained an almost “iconic” reputation over the decades: A Class A power amplifier - the Krell KSA 100 reinforced with “studio handles” - marked the starting signal at the time. The topic of "D / A converter" had not been overslept, either, at the end of the 1980s. Nevertheless, the Vanguard Universal DAC being tested here is "the first standalone DAC from Krell for over 20 years", as the manufacturer proudly announces.

To be or not to be?

However, "standalone DAC" falls short: The Krell Vanguard Universal DAC is equipped with an Ethernet interface and is therefore a genuine streamer / network player . The streaming module used is not an off-the-shelf solution, as the German sales department emphasizes: a particularly high-quality clock, high clock precision and low interference were the top priorities in the development of the module, which was carried out in cooperation with an external specialist.

It is often still underestimated that the supposedly profane streaming process has crucial sound relevance in addition to the actual conversion and subsequent analog signal processing. The actual significance can be demonstrated quite impressively by high-quality streaming bridges à la Auralic Aries and even more so by the SOtM-sMS-200ulta .

The word standalone DAC may also go a little too far: If many people now take a USB-B interface for granted with such a device, it shines in our subject's absence. For this purpose, a stick or a hard disk can be plugged into the American via the USB-A socket on the front, which means that a "Vanguard Universal DAC Server" appears in the home network - an extra NAS server is therefore not absolutely necessary. The American can also be wired using S / PDIF (optical + electrical) or HDMI. Last but not least, the Krell Vanguard Universal DAC can also be managed wirelessly via Bluetooth aptX . Analogously, the music data are then released via RCA and XLR , and HDMI is available as a digital output.Digital + analog

On the chip side, Krell opted for the trendy, high-end 32-bit ESS9018 DAC, which would be called for even faster things, but nonetheless converts up to 192 kHz / 24 bits in the Krell Vanguard Universal DAC (Toslink naturally a maximum of 96 kHz).

On the network side, the Krell Vanguard Universal DAC is easily compatible with local UPnP / DLNA servers (NAS), in my experiments a MinimServer established by my SOtM sMS-200ultra served as the data provider. It could not only be controlled from my iPad using the "mconnect" app recommended by Krell, but also easily via the "bubble" -reinforced Android tablet - including volume control. In addition, the Krell is prepared for Roon (Roon Ready), hooks up with Spotify, Tidal and Deezer and dives into the depths of the Internet radio on command.

But the Krell is not a pure digitalo, it also has an analog soul and can therefore serve as a volume-regulating preamplifier: According to Krell, the class A circuit domain of the Vanguard Universal DAC corresponds to that used in the preamplifier Krell Illusion 2. Almost four years ago, I myself hosted the top model Krell Illusion , one of the best preamplifiers that I have ever heard - extreme discoloration and permeability are among his cardinal virtues. The analogous kinship between the Universal DAC and Illusion 2 also fits in with the fact that the energy supply to the DAC is classic audiophile: Instead of a switching power supply, it is based on a weighty toroidal transformer.If you want, you can also deactivate the volume control - whereby we would then be in the menu settings of the Krell Vanguard Universal DAC, which can be carried out using the metal remote control knocker included in the scope of delivery, also suitable for self-defense or for home improvement: Among other things, different input sensitivities can be regulated Contrast of the display or its automatic switch-off (15 to 129 seconds). Software updates are also possible.

In practice

Speaking of display: The Krell also comes across as robust, high-quality and straightforward-professional - yes, somehow the American radiates something pleasantly serious - that would be around 12.5 x 2.25 centimeters "display slot" in addition to the missing USB-B - Entrance a point that could be criticized in terms of "practicality". Not at all, because you actually have to crouch in front of the rack with the remote control if you want to rummage through the menu settings with a clear eye - after all, you rarely have to do it anyway. The volume indicator on the right in the upper display line is more relevant: it is more of a guessing game from a few meters away, especially if you look down on the device populating the lower rack level.

Krell Vanguard Universal DAC: hearing test & comparisons

Sometimes, some manufacturers surprise by the fact that they like to break with sound philosophies that have been cultivated in the past: I think of Marantz, for example, a manufacturer that now has some perfectly straight and, in my opinion, perfectly coordinated components in its portfolio, such as the recently tested PM8006 or the somewhat older NA 8005 . With regard to the tuning of modern Krell components - the S-300i made in China at the time - on the other hand, I have a very clear expectation: neutral tuning, but deep bass, high dynamics and resolution.

But let's connect the Krell Vanguard Universal DAC and hear what it has to say about such expectations. I mainly tested via LAN, as I said, the server (MinimServer) was my SOtM-sMS-200ultra (with power supply upgrade around 1900 euros) using a plugged-in USB hard drive, which is connected to the network together with the Krell DAC via a Lancom switch . For comparison, my Linnenberg Telemann , a DiDiT DAC 212SE , my NuPrime DAC-10H and my "good old" electrocompaniet ECD 2 are available. In contrast to the Krell, all of them are pure DACs, which are fed by USB from the SOtM mentioned - then not as a mere server, but rather as an audiophile renderer / network player.

First of all, for the sake of completeness, anyone who thinks that a "normal" computer reinforced with a good media player plus a very good USB DAC will sound close to such a streamer / DAC combination as the Vanguard Universal DAC is wrong. Even my formidable, at least 4,400 euro heavy Linnenberg DAC, in a direct comparison to the Vanguard, takes a slimmer, spatially less focused approach, it is supplied with music data by my sound-optimized Windows computer via USB-B. As already mentioned above, this makes it clear that the sound is not only important for the DAC, but also for its digital player. And suggests that Krell actually took audiophile care when integrating the streaming module into the Universal DAC.

oystein sevag bridgeBut also in direct A / B comparison between a combination consisting of NuPrime DAC-10H and SOtM-sMS-200ultra (3,750 euros in total) and the Krell Vanguard Universal DAC, differences can easily be heard: The fine, sustained, space-filling cymbal sounds in Øystein Sevåg's "Hanging Gardens" (album: Bridge; listen on Amazon ) conveys the Krell noticeably more delicate and open. As if he climbed a few more rungs on the ladder in the direction of the super high tone, which certainly also a mite contributes to his somewhat higher "fine pixelity" and suppleness. The stage that continues in the course of the piece via a succinctly captured soprano saxophone, flute and piano finally appears more open and somewhat larger, yes more involved, when it comes to the Krell DAC. Sure, we are dealing with digital sources here, said differences are therefore not as clear as is to be expected when comparing different loudspeakers, but will be particularly catchy about good systems.

Dysrhythmia Test of SubmissionNext we connected the Electrocompaniet ECD 2 with the SOtM-sMS-200ultra (together 4,290 euros). Due to its variability and highly accurate, unadulterated sound characteristics, the SOtM is a very practical, incorruptible and therefore very helpful tool, not least for comparisons like this. The Norwegian ECD 2 (2,390 euros), on the other hand, is no longer the very youngest, but is still up to date in terms of (fine) dynamics and high-frequency openness, and is a good benchmark for comparison across price ranges. Listened immediately, it was confirmed that the Krell Vanguard Universal DAC was one of the components that characterized linearly up to the highest levels. And if he draws the upper layers as free from whitening or a special golden shimmer as the Electrocompaniet, I find the tones of our test subject to be more tonally integrated in the rest of the action and more organic in tone : cymbals and hi-hat in dysrhythmias "Running Towards The End ”(album: Test of Submission; listen on Amazon ) come across the Krell succinctly as it should be by pure teaching, but in comparison appear to be freed from a final diffuse note and a bit more“ deburred ”. The Electrocompaniet / SOtM combination and the Vanguard Universal DAC meet dynamically on an equal footing and can be counted among the quick representatives of their guild, both here and there. I would not point out any differences regarding the bass draft either. Rather in terms of timbres and spatiality: with the Krell Vanguard Universal DAC, the electric guitar not only sounds a bit more substantial, but also receives a clearer focus, with a more defined outline. By the way, what I personally really appreciate is that it just pulls you a little bit more convincingly into the recording.
If you wiggle the DiDiT DAC 212SE into the rack and network it with the SOtM player (a total of 5,900 euros), after a few comparative rounds of listening with the Krell, a “rather a matter of taste” comes to mind: it plays in terms of tonal color purity, differentiation ability and spatial definition of instruments DiDiT recently characterized very aptly by Benjamin Baum on a comparably very high level as the Krell Vanguard Universal DAC. Nonetheless, both devices are aimed at different types of listeners: the slightly toned, supple DiDiT will surely appeal to the "relaxed pleasure listener", while the Krell will rather appeal to jagged dynamics and uncompromising tonal neutrality. The Krell clearly applauds me, but I'm pretty sure that colleague Baum would have decided otherwise ...

I find the final duel between the Krell Vanguard Universal DAC and my top reference Linnenberg Telemann particularly exciting, which has been an integral part of my rack for some time now together with the aforementioned SOtM sMS-200ultra including power supply upgrade. In the test by Martin Mertens from February of this year, the Telemann said: "Resolution, fine drawing, reproduction of details - the Telemann takes these aspects to a new level", the bass also offers exceptional control and accuracy, and "the Telemann mimics the model boy rhythmically" .

Blur The Magic WhipIn Blurs "Ice Cream Man" (album: The Magic Whip; listen on Amazon ), the first thing that stands out is the four-beat beat of the bass, enriched with plenty of sustain: in terms of depth, vehemence and precision, both solutions sound absolutely official and at eye level. Incidentally, the somewhat idiosyncratic bass beats are a real stumbling block - in any case, it is no easy task for HiFi to deliver them dynamically contoured and in the right tonal dose, as I know from many listening circles. Both duelists nevertheless solve this in an exemplary manner.

The subtle metallic noises at the beginning of the title, as if rubbing coins together, the rather inconspicuous shaker on the left channel or the abruptly starting basin: the Krell as well as the Linnenberg have minor issues, fine textures and nimble transients / SOtM combo absolutely on it, certainly not least because of their absolutely gris-free, pure, focused playing style. The Linnenberg / SOtM team allows a somewhat more fluent gait to shine through, which nonetheless does nothing to detract from its precision and dynamics. The Vanguard Universal DAC Krell, on the other hand, places a little more emphasis on the attack phase of tones, thereby appearing a bit crisper and more appealing, which, however, also does not affect its long-term suitability and naturalness.

Outwardly unspectacular, designed for a modern digital device quite old school, but manufactured very solidly, the Krell Vanguard Universal DAC also presents itself as honest skin.
 Of all the DACs mentioned in the test, he deserves the title “dream of every sound engineer” the most. Precise resolution, jagged attack and incorruptible neutrality are responsible for this among other things. What I think should also distinguish a high-end device, however, is this typical, but nevertheless difficult to describe conclusiveness, effortlessness and catchiness, which separate extraordinary audio solutions from the hifi chaff and are ultimately the keys to an organic music experience. In this regard, too, the American "delivers". Nevertheless, the bottom line is not so much aimed at beautiful, soft, or warm listeners as at listeners who above all appreciate an uncoloured, straight sound.

The Krell Vanguard Universal DAC is characterized by ...

 

  • a neutral, no-frills adjustment that could also serve as a standard for other devices.
  • a real “full-range sound building” that effortlessly builds up from the deep bass cellar to the top frequency floors.
  • high dynamics - whether rough bass impulses or fine transients, the Vanguard Universal DAC is one of the most agile components I know.
  • factually balanced mids and honestly accurate highs without undue hardship or sharpening, but also without extra charm. Even if I have little idea of ​​cars: The Krell offers the chassis tuning of a sports car that is permeable to uneven roads, rather than a pleasant limousine feeling.
  • a high resolution, also the spatial differentiation / location accuracy meets the highest demands. The dimensioning of the stage is based on what the music template gives.
  • unexcited, "tool-like" design and robust, professional, studio-like processing. Only the incomprehensibly small volume indicator on the display reduces the practical suitability. Some listeners may also miss a USB-B input.
Audiophile-grade streaming is a growing area and incorporating all the electronics into a single component is going to attract many people. put the Krell K-300i on your audition shortlist
Chris Thomas

SUMMARY: Drawing on its well of power and coupling it with notable resolution proves to be a winning combination for the K-300i. It has even found favour with Naim Audio die-hards (no easy task), who view the K-300i as something akin to a ‘SuperDuperUniti’. So, purely as an integrated amplifier, the Krell-300i is a winner. The Krell has an excellent taut tonality that stays this side of ‘lean’, has power to burn and can deliver it into all sorts of speaker loads with speed and sure-footed dynamic stability. Like all good amps, it imposes itself on the music yet never gets in its way and the 150 watts into 8 ohms is going to be ample for all but the more extreme systems and locations. So far, so good, but the K-300i becomes a different proposition entirely with the addition of the digital board, and for the extra outlay, it is well worth it. Audiophile-grade streaming is a growing area of the market and incorporating all the electronics into a single component is going to be attractive to many people. If you’re one of them, you should certainly put the Krell K-300i on your audition shortlist. 

REVIEW: The first time I heard the name Krell was in the 1956 sci-fi movie Forbidden Planet that was a remake of Shakespeare’s The Tempest but set on a world far, far away. Glorious colour and Theremin-fuelled range of sound effects, groundbreaking at the time, leant an atmosphere of shimmering scientific achievement. The extinct Krell were so technologically advanced that they had driven themselves to extinction, leaving behind their accumulated knowledge in the shape of great glistening machines of unimaginable power. 

Fast forward to the early ’80s and the name Krell makes a re-appearance on British shores as an American audio amplifier called the KSA-50, followed by the 100. It was affectionately referred to here as the first high-end solid-state amplifier, and it certainly had its advocates. It seems odd to reflect now that what we might call the British high-end, the Linn/Naim axis, was one of the only complete systems that made much sense. Love it or hate it (and some did both), it bought the system approach into stark focus. Though the worthy Krell had no ready-made supporting cast, it often found itself driving a pair of Apogees, perhaps coupled with an Audio Research preamplifier. But the important thing was that there was an American amp that wasn’t only good in a straight line. It went round corners too. Dan D’Agostino and Krell had arrived.

You can research what happened next, but eventually, like many companies, new investment was sought, lots happened, and by 2009 the entire D’Agostino family connection was broken. They were out, but Krell ploughed on. As per usual, there were all sorts of criticism alongside the new funding. The usual post-takeover stuff really and it has been no surprise to see that Krell has now dug deep and gone back to what it has always done best. The entry-level K-300i I have been listening to is a US-made integrated amplifier that embodies some of the original amplifier’s solid virtues, certainly in so far as it looks like a Krell anyway.

This solid-cased design, with its bow-fronted central section, is an integrated design that is easy to equip thoroughly for today’s audio environment. The K-300i can be a straightforward amp with separate source components like a CD player or a turntable (though it has no onboard phono stage) or supplied with a digital module that certainly enhances its scope considerably. This latter configuration is the K-300i’s defining character because it becomes a powerful digital hub. If you like your audio system as compact as possible and want to keep the component count down, then a K-300i plus access to one of the primary subscription streaming services makes the three-box system (one-box amp/streamer/DAC and a pair of speakers) an attractive proposition.

It’s a handsome thing (silver in this case) and heavy too at around 20 kg due, in no part, to its dinner-plate-sized 771 VA transformer. It runs using Krell’s i-Bias circuit topology that reduces heat and draws less power than their original Class A designs. It is also very well equipped as far as inputs go. Three RCA and two balanced XLRs are the analogue options and there is a preamp out too. Digital inputs, with the optional card fitted, include three HDMI sockets, two of which are for inputs plus a solitary out. There are a couple of USB connections as well. On the rear panel, you’ll find a USB-B, and on the front, you can utilise the USB-A, should you want playback from a memory stick. It also offers both S/PDIF coaxial and optical options and a single pair of splendid speaker outputs with spade lugs or 4mm connectivity.

The digital card is based around a DAC from ESS and can function as a full network renderer. It can deal with the usual file formats up to 192 kHz/24-bit and will even do DSD up to 128. It caters for all the quality online subscription services as I mentioned, including Tidal and its MQA encoded Masters. For those who prefer the superb productive music surfing environment of Roon, the Krell is ready to be utilised as an endpoint for a Roon core. There is a good Krell Connect app too. Oh, and it also has Bluetooth wireless streaming. So, pretty well equipped I reckon for just about every current eventuality. It’s easy to set up and has a comprehensive remote control. Through its menu section, you can individually name each input and even equalise their levels if you so choose. A neat but small display window allows you to control the menu section and the day-to-day operation of the amp well.

I used this Krell with both a dCS Vivaldi CD player and streamed music using Tidal through Roon while the speakers were the splendid Wilson Duette 2 all hooked up with some Nordost cabling. At 150 watts into 8 ohms, doubling up to 300 watts into 4 ohms, you might expect the Krell to be something of a powerhouse. It is, but the Krell doesn’t just rely on muscularity to achieve some very musical results. Its low-level achievements are excellent, and those late-night listening sessions find the amplifier still weighty and robust through its bandwidth, and this came to become one of its defining strengths at any volume level. The sheer density and breadth of the music is always compelling, as is the driving nature of the bass. 

Listening to Soul Insight from The Marcus King Band [Evil Teen] the amplifier has the sort of taut rhythmic impact that is so much a part of his music. With shades of the Allman Brothers, this draws its influence from the southern states. Its robust and solid bass and drum-propelled driving rhythms are intensely ‘live’ in feel, and King’s voice has that smokey throated soulful sound offset by his thick and honkey Gibson 345 guitar. For someone in his early 20’s King plays with an attack and a ferocious depth of technique that is remarkable. The Krell has an air of relentless push when confronted with this and kicks the rhythm section into the room, giving the drummer plenty of leeway to charge around the kit while the bass is so pervasive and articulate.

The amplifier has a fantastic grip and shows the recording for what it is. The music reminds me of rock bands of the ‘70s and ‘80s but in the right way. It’s electronically tight and rhythmically loose at the same time and the Hammond organ that feels like a real throwback is tasteful and often used as a thickener for the overall weight and density of the music. The K-300i shows it to be brim-full of flavour. The sound is completely integrated and rhythmically to the point and on this album maintains the raw feel that is so absolutely essential for it to work. When listening to this through the Krell, I didn’t want to sit back and peel the audio layers away, and I never felt like examining anything in minute detail. The performance is all about freedom, soul and impact and the joy and musical exuberance of just playing together. In other words, the Krell can get down and dirty and listening to it is genuinely an exciting and compelling experience.

Flip that musical coin and take a listen to Madison Cunningham’s latest album Who Are You Now [Verve Forecast, MQA version] and you will hear how the Krell, tasked with a very different set of musical challenges, becomes an entirely different animal indeed. Madison is one of those singer/songwriters who comes along rarely and again, for such a young artist, seems to have accumulated a lifetime’s experience from who knows where? Shades of Joni, Shawn and Rikki are all there, hanging in the harmonics and the Krell’s intimacy is gentle yet persuasive with a beautiful separation between the vocals and the beautifully arranged instrumentation. Now, this is the kind of music to walk in and investigate so you can take your time and look closely at the components and small details that slot together so well to make the whole. You can listen to the poetry of the pieces and find their meaning and appreciate how the various reverbs have been so masterfully judged to bring the words to life. Of course, you get a front-row seat to the production and the way the producer has given the material life. It’s the sort of joined-up performance that one usually associates with high-end pre/power combos. 

When I think back through the amplifiers that have left their mark, I tend to recall them through a single listening session or even a solitary piece of music that brings together their technical abilities and their ability to connect emotionally. With the Krell, this happened for me after watching the TV presentation of Joni 75, the celebration of the wondrous Joni Mitchell’s 75th birthday. Her songs, performed by various artists have become etched in my mind over the years. I thought I knew them and their secrets but this celebration gave them new relevance for me. It’s not the greatest of live recordings, and MQA hasn’t transformed it into such, but the respect that the artists show to these gems is fantastic. Seal’s take on ‘Both Sides Now’ has a fragile delicacy and a poignancy within those lyrics that is incredibly moving, while Marisoul (backed by Los Lobos) singing ‘Nothing Can Be Done’ shows these songs live on and find new meaning for each generation. The intimacy of the Krell-based system took the listening experience to memorable level and surely we are all looking for systems that can do that.

 

John McLaughlin’s live version of the flowing river that is ‘Lotus Feet’ from the astonishing Remember Shakti album [Polygram] is so crammed full of the most delicious tonal and rhythmic suggestions. Yet, it merely drifts by on so many systems. Even some ultra-expensive set-ups that I have heard render it as a series of percussive events linked by some noodling bits of Bansuri (bamboo flute) and guitar. The Krell showed its tonal deftness. With a drone instrument throwing a distant sheet of shifting shade and light, the band work the meandering and elusive melody in and out of the themes. It has the space and time to be understated and yet to draw you in. 

Jackson Browne’s ‘Live Nude Cabaret’ from Time The Conqueror [Inside] is where the Krell shows its uncanny ability to grow very wide image-wise. It describes a different and even deeper musical landscape and acoustic with depth and a rock-solid bass line rolling underneath the whole event, creating time and ambience. Not every amplifier has the gentle confidence of the Krell on this song, but its overall clarity and taut power always work to bring the music alive. The production is sparing with nothing superfluous in the mix. It was delicious through the Krell, which is very fine at controlling musical perspectives and gentle dynamic shifts as well as tonal landscapes. 

Drawing on its well of power and coupling it with notable resolution proves to be a winning combination for the K-300i. It has even found favour with Naim Audio die-hards (no easy task), who view the K-300i as something akin to a ‘SuperDuperUniti’. So, purely as an integrated amplifier, the Krell-300i is a winner. The Krell has an excellent taut tonality that stays this side of ‘lean’, has power to burn and can deliver it into all sorts of speaker loads with speed and sure-footed dynamic stability. Like all good amps, it imposes itself on the music yet never gets in its way and the 150 watts into 8 ohms is going to be ample for all but the more extreme systems and locations. So far, so good, but the K-300i becomes a different proposition entirely with the addition of the digital board, and for the extra outlay, it is well worth it. Audiophile-grade streaming is a growing area of the market and incorporating all the electronics into a single component is going to be attractive to many people. If you’re one of them, you should certainly put the Krell K-300i on your audition shortlist. 

I just loved listening to this system.
Jason Victor Serinus |

SUMMARY: Dean Martin’s voice, on LP, sounded drop dead gorgeous. The sound was open and inviting,  I could hear every overdone portamento, every little extra bubble of sentiment-laden vibrato. 

Krell Illusion II preamp and Duo 300 XD amplifier, 

 

Krell’s immensely energetic Walter Schofield was in the middle of a system description when I entered the room, so I didn't know exactly what I was hearing, but whatever it was, the fact that I’d just submitted my review of the Krell K-300i integrated before boarding a plane for Denver left me very eager to hear it.

Dean Martin’s voice, on LP, sounded drop dead gorgeous. The sound was open and inviting,  I could hear every overdone portamento, every little extra bubble of sentiment-laden vibrato. But as gorgeous as the sound was, I also knew that the plush midrange of Martin’s voice, like the warm core of Ella Fitzgerald’s instrument, rarely fails to show off a system to best advantage. I needed another sample.

On another track, James Taylor’s “Her Town Too,” there was no fall-off in transparency or pleasure. Once again, the sound was open and revealing, with every bit of post-production reverb exposed. I just loved listening to this system.

As I learned after listening, components included the Krell Illusion II preamp and Duo 300 XD amplifier, VPI's 40th anniversary HW-40 turntable with Fatboy Gimbal 3-D printed tonearm and Audio Technica Art 1000 cartridge the brand new Alta Audio Alec loudspeakers.

KRELL 300XD review from Sweden received a 10 out of 10 rating
Some excerpts below have been translated to English:
 
"My review can surely be interpreted as overwhelmingly positive, and completely without nuance, but, this has been my experience and I stand behind it 100 percent. I am probably both enchanted and brainwashed. Do I mean that life itself will become a lot better and all your worries will be gone if you just get yourself the Krell TRIO 300 XD? – Yes, I actually mean that". 
 
I"f you wonder why the measurement system is called the Cube, then you can understand that exactly after studying this measurement of the 300XD. It can’t get any more cube – like, than this. Also, note the enormous current strength. A Cube measurement in absolute world class".

Click link to read full review:
https://files.constantcontact.com/f50eb4f7201/f32cae3c-feaf-440c-beaf-f2a47489bbb3.pdf

Awards

Hi-Fi Choice Best of the High End award - 2011

Krell is one of the defining high-end brands and the Cipher is a classic example of what it’s capable of when pulling out all the stops. This is a technological showcase that is designed to extract the absolute maximum from both CD and SACD, including multichannel discs. No expense has been spared on the lavishly finished casework, the extensive power supply arrangements and the very sophisticated balanced DAC arrangement. The result is a superlative performer.

KRELL K300 Integrated amp - SOUNDSTAGE - "PRODUCT of the YEAR award 2019"

"Yes, it is in the upper price bracket. On the other hand, when will I own a Picasso painting? K-300i is a work of art, and moreover, a work of art that makes you enjoy other works of art in a truly breathtaking way. Imagine if painters made great paintings for centuries but kept them under a veil that only hinted at their true beauty. Suddenly somebody comes around and pulls the veil away and lets you see the paintings in their full glory, every stroke of the brush and every speck of paint. K-300i did that for me, for the music. Get it if you can."  - SOUNDSTAGE - "PRODUCT of the YEAR award 2019"

Testimonials

Everything about this amp is absolutely superb

KRELL K300, among the best audiophile amplifiers available.

"Krell Performance is as always, not only with endless power, but also has a balance in sound staging and performance that places it among the best audiophile amplifiers available. Thanks to the digital module and other amenities, this is a real all-rounder.”…. PowerHouse Mag (Germany)

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