DarTZeel NHB-18NS MkII Preamp fully balanced

DL 08 PA NHB18
NZ$ 49,995.00 ea (incl. GST)

one man’s uncompromising passion for music and its reproduction

A New approach to Preamplification 
The darTZeel NHB-18NS is the logical partner to the now legendary NHB-108 model one power amplifier.
In keeping with the very same philosophy, darTZeel uses dedicated circuits reduced to their most basic form. Here again, there is no application of any overall negative feedback. The delicate, small audio signal amplified by the NHB-18NS only passes through 7 silicon junctions from input to output, including the 11 dB full discrete gain stage. For the phono stage, we only add 6 junctions, for a maximum additional boost of 66 dB (77 dB in total).
The advantages of these new circuits, whose designs are patented, are in the same league as the NHB-108 power amplifier: an extreme, pure sound quality never achieved before.
Leading-edge audio electronics 
At this level of performance, every detail is of prime importance.
The delicate, small signal delivered by the sources is amplified by discrete devices, or by means of matched transistors embedded in dedicated integrated circuits. No operational amplifier is used in the entire signal path. As for the NHB-108, all components used in the NHB-18NS preamplifier, with no exception whatsoever, are based on the finest products being produced by leading-edge industry at the present moment.
The first aim of the NHB-18NS is to provide sound reproduction quality Never Heard Before.
Instead of offering a preamplifier based on the same approach as that of our competitors, we at darTZeel chose to think differently, offering for the first time in the world what previously seemed impossible:
- No contact or switches or relay of any kind for the selection of the sources. This revolutionary feature brings a new level of transparency. Instead of routing the signal through a selector box, each input has its own dedicated gain stage, which is enabled or disabled according to the user's choice. The signal is then directly routed to the volume control module.
- A whole new volume control module, which completely avoids the use of any potentiometer, stepped attenuator or analog switch array in the signal path. The sound signal is attenuated in a fully passive way, using special analog optical couplers controlled by a dedicated processor, providing a dynamic range of 96 dB, through 192 discrete steps of 0.5 dB. There is no use of VCAs or any other active component.
Both of these breakthroughs constitute a big step in the right direction: no harm to the signal.
The NHB-18NS is not only new in these aspects. We have also included all the features already implemented in our now famous NHB-108 model one, as follows: 
Only small local negative feedback at the inputs.
One small, symmetrical, local negative feedback in the voltage gain stages.
Open loop, free of all negative feedback for the output stages. 
In addition, the NHB-18NS features advanced possibilities, including the use of multi-amping through darT to Zeel 50-ohm links. Some key features are (per channel): 
1 state-of-the-art dedicated MC phono stage input.
1 XLR full floating input and output.
4 RCA / BNC 50-ohm Zeel inputs.
3 BNC 50-ohm darT outputs, ready for tri-amping, with built-in passive filters which can be user enabled.
1 RCA output.
1 RCA record output (fixed level).
All inputs can be Home Theatre bypassed (troughout gain of 0 dB).
Power supply
The darTZeel NHB-18NS is an authentic dual mono preamplifier, from input to output, with separate grounds for left and right channels.
Each channel is battery powered by its own battery bank, offering 12 hours of listening pleasure before a charge is needed.
A very sophisticated, regulated and dedicated supply for every input and output is provided, ensuring the lowest power supply impedance possible.
A smart automatic function is provided as standard, allowing full battery operation when listening, and charging mode being activated when the preamp is switched off. Hum is gone forever, and there is no need to worry about knowing if batteries need to be charged or not.





Description: Solid-state preamplifier. 
4 xunbalanced line-level (switchable between RCA and 50 ohm Zeel BNC),
1x unbalanced phono (RCA),
1x balanced (XLR). 

1x unbalanced (RCA),
1x balanced (XLR),
1x buffered Tape Out (RCA),
3x 50 ohm darT (BNC). 

Frequency responses (depend on measurement method):
1Hz–1MHz , +0/–6dB;
10Hz–100kHz, +0/–0.5dB;
20Hz–50kHz, ±0.5dB (XLR inputs & outputs). 

THD: <1%, 7Hz–77kHz. 
Signal/Noise Ratio: 100dB (A) line level; >70dB phono. 
Risetime: <0.8µs. 
Slew rate: >88V/µs peak–peak. 
Crosstalk: below –90dB, 20Hz–20kHz. 
Dimensions: 440mm W x 170mm H x 415mm D. 
Weight: 26kg including 3kg power supply.


If you're in the market for a state-of-the-art preamp or just want to hear the results of one man's lifelong passion and brilliance, track one down and listen to it.
Mike Malinowski

Summary review:  
....you cannot go wrong with the 18NS. In fact, if you don't need complex control functionality, you'll be in heaven with the darTZeel. I bet that for many, it will be a lifetime purchase. It is that rarest of breeds, a revolutionary state-of-the-art preamp that breaks new ground with its design, execution and performance. If you're in the market for a state-of-the-art preamp or just want to hear the results of one man's lifelong passion and brilliance, track one down and listen to it. Highly recommended. 

Extended review:
The darTZeel NHB-18NS (Never Heard Before - model 18, No Switches) is Hervé Delétraz's all-out assault on the state-of-the-art of preamp design. At NZ$47,995 (incl phono option) it better not be a me-too product. The most common reference path in preamp design is to combine superb sonics with über-control flexibility. The two-chassis VTL 7.5, Boulder 2010 and Levinson 32 all take this course. These are amazing beasts that can adjust levels, select inputs and in the case of the Levinson, vary the resistive and capacitive loading for your phono cartridge – all from the comfort of your listening chair by remote control. These are no sonic slouches either.
Hervé has taken quite the opposite approach. While not calling the 18NS minimalist, there is certainly no vibrant digital display, no multi-function remote control nor dozens of buttons and switches to be found anywhere. This baby was designed for one thing: to be the finest sounding preamp anywhere at any price. This is one man's lifelong commitment to produce a sonically spectacular device with revolutionary design elements using common off-the-shelf parts, then build it in Switzerland to a standard that should allow it to outlast most of us.
With a build quality that is off the scale, the 18NS has a stunning look that is unique, simple and elegant. One button, two large knobs, and three lights are its prime distinguishing characteristics. The 18NS was designed to be the companion piece to the NHB-108 amp and shares the sonic darTZeel family sound. Far more than sharing just a physical appearance, the circuit design of the 18 is virtually identical to that of the 108. It's fair to say that if you like the 108, you'll love the 18 - and let me tell you, I loved the 108. Hervé is an engineer and designer who truly understands the purpose of musical enjoyment. With unmatched zeal and fully understanding that an amplifier will not cure cancer nor end poverty, Hervé's purpose was not for an edifice to his engineering excellence but to bring ultimate joy and musical pleasure to the listener, with a slight added touch of mischievous whimsy. Did I mention that the 18 includes a superb built-in phonostage? It most certainly does.
Although grossly oversimplified, the darTZeel philosophy is:
(1) Use an exceptionally simple amplifying circuit.
(2) Remove all global feedback and virtually all local feedback.
(3) Provide perfect power.
(4) Design the circuit for exceptional extended bandwidth and minimal phase shift.
(5) Eliminate all switches, relays and traditional volume controls.
(6) Build it to a quality level that would make NASA proud.
This in essence defines the 18 NS.
If you are expecting dozens of controls, knobs and switches for your $20K, then you might be disappointed. The most obvious physical characteristics of the 18NS are two large knobs, symmetrically placed on the front panel, which compare physically to the power lights of the 108 amp. The left knob called Enjoyment Source is the input selector. The right Pleasure Control knob is what most others call a volume control. Both controls have rubberized bands around the circumference and a silky elegance that you must feel to believe. The center on/off button is called the Power Nose (again identical to the 108 amp).
While the 18NS visually matches the 108 amp, I can assure you that it will match nothing else on your equipment rack. No one will mistake this gold and red beauty for any other brand. It's not going to blend in with your other silver and black components but who cares? This sucker was built for sound, not to blend in. Don't get me wrong though. While the unit is visually different, it really is stunning. If colour or style matching are your prime concern, however, there are certainly other routes to go.
This is one heavy piece, weighing 23 kilograms (50 lbs) with 16mm (.63 inch) thick front panels, 10mm (.4 inch) side panels all evidencing fanatical attention to milling and construction. This is obviously a no-compromise component which was not made to a price point. It is elegant and sophisticated in design, meticulous in execution.
The rear panel
Unlike the simplicity of the front, there's a little more going on in the rear. In addition to the standard single-ended RCA and balanced I/Os, there are fourteen 50-ohm connectors which darTZeel calls Zeel inputs and outputs. More on this later but they are an important element relative to Hervé's vision of sonic perfection.
A small toggle switch below each input allows switching between various grounding schemes if you run into hum problems. Select either chassis ground, earth ground or floating ground. Line inputs one through five are switchable between single-ended or Zeel inputs. A small toggle switch below each selects between single-ended, Zeel or a 6dB attenuation setting. Input number six is for XLR balanced sources with a switch toggling between standard 600-ohm impedance for professional gear and 6dB attenuation. Another switch offers various grounding paths for minimizing ground loops. Standard outputs include balanced XLR, RCA, a single buffered recording output and three buffered Zeel outputs which, with optional filters, can be used to feed the 108 amplifier for either bi-amp or tri-amp applications.
Remote control
You can't get much simpler than the 18's remote, machined from a solid billet of aluminum. It's heavy and well-balanced but really does only a few things: raising and lowering the volume, full muting and turning the front face panel indicator lights on and off. The design is minimalist squared. If you're looking for a remote to control the universe with like the VTL 7.5, look elsewhere. Because the 18 doesn't have digital readouts, pressing volume up or volume down causes the three fascia indicator lights to momentarily flash green, indicating that the unit is receiving volume change instructions from the remote, a neat little feature. As to input source changes, Hervé's philosophy is that if you're going to change a source -- from phono to CD let's say -- you have to get up anyway to cue the record or load the CD.
According to Hervé, the fundamental problem in amplification is transient intermodulation distortion (TIM) which occurs "when the negative feedback loop is in a state of overflow which is something that arises more often than you might think since a negative feedback loop correction always applies after the phenomena to be corrected appears. During these very short instances, the amplifier can produce more than 100% THD and/or IMD." In darTZeel speak, this is temporal distortion. The other contributor to temporal distortion is phase shift, especially at very low and high frequencies. Hervé challenges listeners to look at a square wave response of an amplifying circuit at, let's say 40Hz, not just at 1k or 10k. Although a square wave at 40Hz might have an excellent rise time, significant tilting at the top indicates problems. "Ideally the amplifying circuit should reach 10 times lower and 10 times higher than the audio band to maintain correct phase. Our circuits extend 50 times lower and 50 times higher... at 20Hz we are quasi flat ... at high frequencies we extend to about 1MHz - 50 times more than 20kHz to obtain 1° phase shift at 20kHz."
According to darTZeel, eliminating phase shift and global feedback solves the temporal distortion problem. Therefore, all darTZeel amplifying circuits operate only with small local negative feedback loops instead of a global loop. It is an interesting academic solution in theory but apparently difficult to execute in practice. High bandwidth generally requires global feedback, and low feedback equals poor frequency response. It's taken Hervé 20 years to develop and perfect his solution and the interview following the review will shed some light on specific design implementations.
Back to the front panel. The only other knob there is a small balance control and like most things here, it is slightly different. There is no audible difference in balance until the balance control is moved approximately 5° off center. When you're close to the center position, the system keeps the channel balance exact. A full turn right or left equates to 3.5dB maximum cut, automatically boosting the opposite channel by the same amount for a maximum of 7dB tilt. This allows for an exceptionally fine tuning of the overall soundstage without affecting the overall volume, permitting utterly precise imaging and balance control.
There also are two small spring-loaded switches for mute and stereo/mono. The central front panel LED glows yellow when the preamp is operating in the battery mode and red when charging. The other two LEDs indicate red or green for mute and stereo/mono. There are two small red indicator lights on the enjoyment and pleasure knobs to indicate their relative position. The LEDs are innocuous to me even in a darkened room but can be turned off. A home theater bypass mode is provided.
Again, you don't switch an input, you "enjoy a line source". A quick twist of the enjoyment knob allows you to change your enjoyment from one input to another; with about a one second delay and a soft audible click, your enjoyment begins.
Battery Power
Very few designers have successfully implemented battery power in preamps. I can think of ARS Emitter, Dodd, Edge, Silvaweld and Sutherland in this esoteric realm. Separate, massively filtered, regulated power supplies are now de rigueur in reference equipment. Therefore, one might question the need and trouble for both the designer and the end user to rely on battery power. My current VTL 7.5 and the Levinson 32 are perfect examples with power supplies as large as the amplifying section. They also weigh as much as a small power amp.
Many people leave their preamp on continuously to keep it in a ready-to-use state. Preamps draw relatively little power, therefore this is accepted behavior. It does not apply to the 18NS. Its battery power and automatic charging circuit preclude this. The battery system is designed to continually power the preamp as long as the batteries retain a charge. Upon discharge, the charging circuit turns on, the preamp converts to AC power and the LED on the front panel turns red to indicate charging. When the battery is charged, the indicator light returns to yellow in an automatic and continuous cycle. If you leave the preamp powered up nonstop, you'll never know the relative state of charge or discharge. You could sit down for an all-night listening session and the batteries could enter their charge cycle. Instead of listening to battery power, you're then listening to AC. It's not the end of the world. On AC the 18NS is still one of the world's best, it just loses some of the magic. There's a loss of transparency, purity and a slight increase in grain. So just turn the 18 off when you're done. Once it's broken in, it doesn't matter because it has a relatively short warm-up. After five to ten minutes in my informal tests, it's ready to go. Also, leaving the unit on causes a constant cycle of charging and discharging which will shorten battery life. The outboard supply includes the battery charging system and serves as backup power should the batteries expire. Under normal charged-battery listening, the power supply "disconnects" automatically. If you listen while the red light goes red, every minute in red mode means two minutes of battery life. If after 10 minutes of playing while charging you power the preamp off and on again, the machine will play on battery mode for 20 minutes. It means that one doesn't have to wait for a full charging cycle to enjoy battery mode. Battery mode is preferred at every power-on until battery level really needs a charge.
For me, that's a quick terminal cleaning with alcohol, an application of Walker Audio's Extreme SST contact treatment to a few connections, a push of the 'power nose' and we're ready to go. My initial unit was delivered new from the factory and I used the Stereophile break-in CD for approximately 100 hours before any serious listening. Upon initial listening, a minor glitch arose in the unit when the volume control was advanced to moderately high listening levels. After a return trip to the factory, the problem was quickly resolved. Not knowing how much playing time the unit received at the factory, I continued my break-in for three or four days while listening intermittently along the way. The sound of the unit remained consistent during this three to four day break in. The bottom line is that due to the unit's return to the factory, I cannot definitively state the required break-in time. If the 108 amp is indicative, and based upon the similarity of the circuit design, I would recommend a considerable period. There is some ongoing bickering in the audiophile community related to buying megabuck components and then being forced to spend time breaking in the product. Personally, I could not care less. For many people, the darTZeel is a lifetime purchase. Allowing a week's break-in is no big deal. Cars and other mechanical devices have break-in periods and to my ears, virtually all new electronics benefit. Get over it. Worry about important things in life.
The sound
Let's end the suspense - as if there was any to begin with. I was blown away by this preamp, especially its air and transparency. The sound just doesn't emanate from the speakers, it soars. On Plas Johnson's Positively [Pure Audiophile records], Johnson's tenor sax floats with wonderful precision in the room. Glenn Miller's Orchestra's direct-to-disc [The Great American Gramophone Company] is a challenging record to reproduce; the lightning fast transients, bold dynamics and intense brass of Tuxedo Junction shows off the 18's ability to nail dynamic contrasts.
Transient response, a seamless soundstage and a top-to-bottom coherence place the 18NS at the top of the charts. Think electrostatic and Kharma speakers. When set up properly, both produce a most wonderfully coherent and seamless presentation. The 18NS is the electronic component version thereof. The comparison of course is conceptual. I'm not saying that the darTZeel will make your system sound like a Sound Lab or Karma Exquisite. What I am saying is that these components bring a seamless focus to the table. The ability to hear and resolve various instruments in real space without any artificial etch puts the 18NS in rarefied strata.
Every amp or preamp in my experience exhibits some degree of smearing, often as the music increases in complexity yet the 18 preserves clarity regardless of the musical complexity. Almost any system can reproduce the first half of Ravel's Bolero [Stanislaw Skrowaczewski, Minnesota Orchestra, Reference Recordings] in its utter simplicity. About halfway through when the strings make their entrance, the wonderful initial eloquence at times can bog down as the ever increasing complexity congests low-level detail. When the horns enter, the chaotic crescendo can leave many components in the dust but the 18NS keeps consistent focus and resolution with zero stridency.
Transparency, Clarity and Resolution
By no small margin, the 18NS is my personal champion in the resolution arena. It offers remarkable transparency. When it comes to coherence, detail and resolution existing within an extraordinary musical framework, the d'art is in a class by itself, revealing the source with no definable euphonic coloration. It's one thing to extract detail from a small jazz ensemble; quite another for a full orchestra. Playing with the delicacy that is the "Meditation" by Jules Massenet from Clair de Lune [Raymond Agoult, London Symphony Orchestra, Classic Records], all sensuous and soothing, the 18NS provides a wonderful balance between micro-dynamic clarity and liquidity.
The Brazilian sleigh bells in Hi-fi A La Española [Fennell, Eastman-Rochester Pops, Mercury] are light and airy, displayed with precision and perfect musical balance. I've heard them too soft and round and at other times harsh, grating and sterile. The 18 gets it just right.
Don't confuse the fundamental difference between clarity and apparent clarity. To use a video comparison, turning up the video sharpness control might have the appearance of more detail but in reality it obscures the smallest details. This is provable by test patterns and by people far more knowledgeable than me. In the audio analogy, the 18NS defines the difference between clarity and apparent clarity.
As a personal favorite and challenge to the system, Nat King Cole's Greatest Hits [DCC] is an amazing record, especially realizing that the music was originally recorded 40 to 50 years ago. It offers wide dynamics and -- when all the gods are in alignment -- a spooky, eerie in-room presence. With "Orange Colored Sky", the brass is right on the very edge of harshness and slightly aggressive. Played with sub-par components or misaligned VTF/VTA, you will quickly cover your ears to hide. Go too far the other way towards warmth, lushness and tubiness and you get dull, boring, and overly sweet. The darT nails this one too.
Some components can flesh out a vivid soundstage but have a somewhat fuzzy indistinct area between the individual instruments. The overall soundfield might appear exact but not real when compared to live music. This diffuse nature in defining the air around the instruments betrays the music as a reproduction. Whether it's the extended bandwidth, solid phase response or some other design criteria, the darTZeel preamp and amp are clearly in a class by themselves when it comes to fleshing out the air and distinct area between instruments.
Every high end manufacturer aspires to build components to convey the sound with a minimum of electronic artifacts. Excluding the theoretical "straight line with gain", every electronic device unfortunately has a character and therefore, artifacts. You might like them and they may sound good to your ears, but they impart electronic characteristics different from the original music. Don't kid yourself, the 18NS will not magically allow an orchestra to appear life-sized in your living room either. What it will do is strip away more of the artificial nature of reproduction, allowing you to get lost in the music with a deep emotional immersion. There is a purity of timbre that favors neither the bass nor highlights the treble. It just has the tonally right feeling of beautiful music. The 18NS simply reduces the artifacts present in most reproduced music which sends audible clues to your brain that you are listening to reproduced music, allowing the music to appear relatively more alive.
The 18 is forceful without the slightest hint of strain. With Dave Brubeck's Take Five, Time Out [Dave Brubeck Quartet, Classic Records] lesser components tend to compress and dampen the dynamic moment of impact when the drums literally explode into the room. Leading edges are softened and trailing edges are at times compressed. Not so with the darts; the drums literally detonate into the room with startling realism.
The 18 scales beautifully from Oscar Peterson's small trio on West Side Story [DCC] to Wagner's Ride of the Valkyries, Die Walküre [Eric Leinsdorf, Los Angeles Philharmonic, Sheffield Labs]. Size is properly maintained. On one end of the spectrum, Peterson's Trio is
not overblown with 10 foot-wide saxophones nor is the Los Angeles Philharmonic compressed. Each is presented in a very natural, precise soundstage. In both instances you can close your eyes and imagine the instruments reproduced with their various intensities with tonally right harmonic characteristics. Another lovely test passed with ease is Mussorgsky's Night on Bald Mountain [Leonard Maazel, The Cleveland Orchestra, Telarc]. From a single haunting violin, through massed strings to a crushing crescendo, this recording will tell you a lot about your system. Once again, the darT acts as essentially a massive pipe allowing the music to flow through unaltered.
My first casual reaction to the darTZeel was that possibly the frequency response was tilted ever so slightly upward with a slight lack of bottom end impact. But then there is a reason reviewers get paid the big bucks. It's for the long-term critical evaluation of components using a variety of sources, not for snap judgments. And over the long haul, it became clear that the 18 did not add or subtract anything. It just revealed.
The bass is distinct, taut and focused, painted not as a single homogenous note but with far more complexity. The sound of the drum from the initial thwack changes and envelops you with a startling top-to-bottom clarity and purity, exceeding every preamp in my history including the magnificent VTL 7.5. This clarity is manifested by the revelation of minute details and nuances buried in the musical event.
Although the bass is as tight and delineated as I've ever heard in my system, it does not have the greatest perceived slam. Hervé hypothesizes that amps with temporal distortion and phase shift cause artifacts that produce large and boomy bass. Hervé cautioned to judge the bottom end based upon the tautness, definition, control and depth - not the perceived amplitude.
If you want clean, loud and deep, this baby loves being turned up. The 18 can rock out with the best of them. "Heartbreaker", Led Zepplin II [Classic Records] which can sound a touch thick, came through crisp, clean and lightning fast. As I mentioned before in my speaker analogy, the 18 shares some characteristics with electrostatic speakers. I fondly recall my Acoustat 2+2s and I referenced them several times in my listening notes. The 18's speed, detail and cohesion bring me back to memories of the Acoustats but with a far more natural midrange (no plasticity), and with a bottom end far deeper and tighter than the Acoustat could ever dream of (of course now I listen to Wilson Alexandrias too).
At the other extreme, the darT presents a wonderful top end that seems to extend, well, forever. Bells, cymbals, chimes are rendered with a shimmer and ethereal beauty, which floats in space and cuts through the other instruments, ultimately fading with a wonderful decay.
We have all heard components with extended highs presented with somewhat of a hardness or texture. Not so with the darTZeel. The 18 renders highs with a total lack of grain, analogous in video to a switch from a standard analog video signal to 1080P HD.
Imaging is life-sized and definitely not overblown, with a soundstage that does not slam you with an in-your-face presentation. While it does extend out from the front plane of the speakers and deeply behind the speakers, it does not throw the listener into the sound field as some components do. The darT presents the music to the listener, it does not immerse the listener in the musical stage. At times, some components can present an exaggerated sense of height. Ella Fitzgerald appearing fifteen feet tall might be exciting in a hi-fi sense but not realistic. The darTZeel nails this perspective perfectly with images scaled very realistically.
Transients are razor-sharp and well defined which in my experience leads to wonderful PRaT (Pace Rhythm and Timing). This speed and resolution allows you to hear many subtle details previously buried in the mix. As a person
been blessed with a high resolution system, I never imagined at this point in my listening career that I would be re-discovering detail and information from sources which I have heard dozens if not hundreds of times. Yet in the past few years, it has happened three times: with the Walker turntable, the Wilson X-2 speakers and now with the DarTZeel amp/preamp combo.
The darts display a fascinating characteristic which I often find in live music - the ability to focus either on only a specific instrument (or group of instruments), or to defocus and absorb the performance as a whole. The theory is that specific brain cells retune themselves to specific sounds and adapt to make a sort of feedback process for auditory focus. Whatever the explanation, I really enjoy this phenomenon and it allows me to listen to music on several levels. Sometimes I want to listen to the individual instruments, melodies and rhythms; at other times I just zone out and listen to the overall musical experience. I find the ability to do this far more often with live music vs. reproduced music yet with the 18, it's pretty easy to choose my focus.
I have been fortunate to hear some great phono preamps both in my system and in other high-resolution setups. The list is among the Who's Who of great designs - Aesthetix, Manley Steelhead, Lamm, Levinson Reference and even my old Krell, which if memory serves me correct was a spectacular value for the money and highly underrated. There are certainly other contenders in this elite class: the Connoisseur and Boulder come to mind. For me the Walker Reference sits as my current preamp of choice. Two logical questions are, how does the 18's built-in phono sound in an absolute sense and how does it stack up to the competition? The first question is easy. Every sonic description about the preamp applies to its phono input as well: dynamics, spectacular detail, ultra quiet backgrounds and an almost unbelievable lack of grain. Without repeating everything, suffice it to say that if you like the 18NS as a line stage, you will like the phono section - guaranteed. They are obviously cut from the same sonic fabric.
How does the phono stage compare with the best? Based on my experience, some general observations. I find the Lamm to be an exceptional and first-rate musical component but just ever so slightly dark. Although the Steelhead offers unmatched flexibility, the Lamm exceeds it in liquidity and emotional involvement. The tubed beast, the Aesthetix, is flexible, dynamic and blooms naturally into the room. When I heard it however, it was not the final word in low noise, although I have not heard the most current upgrade. The Levinson Reference, while good, is frankly not quite in the same league as the others.
Fortunately I was able to compare the Walker and darTZeel phono sections. In my review of the Walker reference preamp, I asked "Does the music touch your soul? Are you emotionally fulfilled after an evening of listening? Are you drawn into the music? Is your body filled with goose bumps? These are what matter most to me." My answer was that the Walker delivered these above and beyond the competition. During the past several years, Walker has not stood still with phono preamp design. My unit has been modified approximately four times during that period. The improvements were not minor and in a head-to-head comparison, I still prefer in the Walker slightly over the DarTZeel. This is not a criticism of the darTZeel's performance but more of a tribute to Walker. It just delivers a little more of that musical magic that keeps one enthralled. Admittedly, the comparison is rather unfair since the Walker as a standalone phono preamp costs over $12,000 - without a line-level preamp. As to the others, moving back in my aural memory, I would rate the entire DarTZeel slightly above the Lamm for its amazing resolution, dynamics and continuity. [At the time of publication, darTZeel's fact-check session informed us of a running upgrade to the phono section. Maintaining the same phono sound signature, S/N ratio has been improved by 8dB and 2 transistors were removed from the signal path. Quipped the designer, "of course this update does not invalidate the current phono stage, it's just a small step toward the logical quest for the Holy Grail..." - Ed.]
What's the deal with Zeel?
Let's take a little detour from the subjective review to examine another one of Hervé's unique design elements built into both his amp and preamp - the Zeel connections. With the hundreds if not thousands of types, brands and price points in high-end audio cable, why does darTZeel believe that we need a new incompatible interconnect system? Further in the mysterious world of cables which have both legitimate manufacturers and a touch of snake oil, what makes darTZeel different? The answer is some pretty interesting science. I will leave it to the engineers in the audience to explore the subject farther but I shall offer a layman's overview.
During his early days in design, Hervé became intrigued with cables though not necessarily from an aural perspective. While he clearly heard differences in design, his fascination really stemmed from his inability to correlate design differences with the ultimate sound produced by the cables. Through his research at the Engineering School of Geneva, Hervé tries to solve this riddle. His research and analysis are above my understanding so bear with me in this rather simplified overview of his work, leading to the development of the Zeel connection.
Before we get started, a couple of basic definitions on impedance and resistance: Resistance is used with direct current, defined as equaling voltage divided by current (R = VD/C ÷ A D/C). Impedance is the alternating current equivalent of resistance (Z = VA/C ÷ A A/C), with both resistance and impedance measured in ohms (Ω). The primary difference between the two is that impedance varies with frequency.
Virtually all modern audio equipment uses low impedance sources and high impedance loads. When this input ratio is ten or higher, all is well, meaning that for example the CD output stage will have no problem driving the input of the preamplifier while offering maximum voltage transfer. However according to Hervé, this universally accepted ratio of ten ignores the inherent electrical properties of the interconnect cable.
Hervé's experiments concluded that mismatched components and cables change and distort the sound. While at audio frequencies this distortion might be low, it is distortion and degradation nonetheless. If there is a better solution, why induce distortion to begin with? Enter the Zeel connection. Precisely matched inputs, outputs and cables offer pure distortion-free signal transfer. As we move from theory to application, the first question is whether it works. Is there a difference between a Zeel connection and a high quality interconnect and could the relatively inexpensive 50-ohm Swiss cable be a giant killer? Well, the sound through the Zeel connections and cables closely matches the theoretical predictions of Hervé. At the low end, the bass seems slightly less forceful through the 50-ohm cable but far more delineated and focused. The other end offers an even more dramatic change. The extension, detail and purity of the highs through the Zeel connection yields a far clearer and cleaner overall presentation.
Donald Fagan's Morph the Cat [Reprise Records] is a superb reference disc. Although I find the music to be highly derivative of his earlier work, sonically this disc soars. Dynamics, deep clean bass, extended highs and vocals - it's everything that you need to give your system a test drive and the Zeel connections delivered it all. A delicate chime on side 4 is clearly present, with just a wonderful presence and decay. Yet with the VTL, it was far more deeply buried in the mix. When the 18NS and the 108 amp are connected with the balanced Transparent cables, the overall sound of the DarTZeel system sounds -- that is the amp and preamp -- slightly more "traditional" than with the Zeel connections. I cannot overstate this. If there never was a Zeel connection, I could be happy with the 18 forever using traditional interconnect. The Zeel connection simply raises the bar with a touch of extra purity, clarity and definition.
Drum roll please: The darTZeel NHB-18NS vs. the VTL 7.5
My source is of course the Walker Proscenium Gold turntable recently upgraded to Black Diamond status. The signal starts with the Clearaudio Goldfinger cartridge through Walker's custom pickup arm wiring on to the Walker phono reference preamp. I bounced between Walker's Silent Source interconnects and Brian Kyles' Xtreme Cables from the phono preamp to the darTZeel. The combo is certainly among the top source components around. With this high definition source material, the sonic comparisons between the darTZeel and the VTL 7.5 were actually rather easy. At first I wondered whether two such exalted pieces might have similar sonic footprints, making the comparison difficult. Boy was I wrong. Any non-audiophile raised on Bose would have no difficulty distinguishing between the two.
Having lived with the VTL for several years, I know its sound intimately. The ability to switch back and forth between the VTL and darTZeel provided a fascinating comparison. The VTL's soundstage blooms farther out into the room. The 18 exhibits a slightly smaller 3-D soundstage but improves upon the clarity within that soundstage. When listening in the nearfield, the VTL immerses you into the music whereas the darTZeel presents the music to you. The VTL has slightly better macrodynamics, the darT the better microdynamics. The darTZeel extends moderately in front of the speakers, approximately 50% of the forwardness of the VTL, but extends very deep behind the speakers, farther than the VTL. Both preamps present a wide soundstage, with the VTL's ever so slightly broader. The VTL is warmer, with a subtle mid-bass emphasis compared to the 18. Here it gets tricky: while the VTL has apparently deeper bass with more visceral slam, the darT is more defined, tighter and has a clear edge in clarity and air. Although the VTL sound appears deeper, rounder and fuller, I refer you to Hervé's caution in comparing the 18's bass response. Do not get tricked into an initial impression that the 18 lacks in low-end. It doesn't.
The crucial midrange in each preamp is smooth, neutral and emotionally satisfying. Again these preamps sound different. The darTZeel wins slightly with its extended highs and that special air. The VTL has a tube-like emotion to the sound while the 18 offers unbelievable resolution. The VTL has a full-featured audio control center while the darTZeel is - well, less endowed. That is assuming six inputs, an integrated phono preamp, recording outputs and three types of primary outputs qualify as minimalist. Do not take these comparative comments out of context. Just because the darTZeel resolves like no other preamp does not mean that the VTL is lacking. And just because the VTL has a luscious 3-D soundstage does not mean that the darTZeel is lacking. Unless you had the ability to switch back and forth between these two in an ultra-high resolution system, you might not draw any of these conclusions. If you are looking for the final pronouncement as to the superior unit, you're not going to get to it from me. At this stratum, both are world-class contenders. When I listen to the darTZeel for an extended period, I am positive it is the one that I want and could live with for the rest of my life. Switching back to the VTL a week later and it could be my long term reference preamp. If you are looking for a definitive verdict, I can tell you that the darTZeel does things especially in the area of resolution and definition combined with musicality that I've never heard before in any component – ever.
In my review of the 108 amp, I described the sound as a superb mix of tube and solid-state, probably leaning slightly more toward tube than that of solid-state. It presents music with slightly more tube-like liquidity than even my VTL S400. Interestingly, the 18NS, which has virtually the same circuit design as the 108, would not be mistaken for tube preamp. It really has no attributable sound. It's pretty close to the sound of the Placette Passive Preamp in neutrality but has far more slam, dynamics and that exciting sense of aliveness. Again don't read more into these comparisons than intended. I'm not suggesting that the Placette -- a great passive preamp -- is in the same sonic ballpark as the darTZeel. It's not. However, both are extraordinarily neutral.
In the end, if you're going to plunk down NZ$47,995 (incl phono option) for a preamp, you better listen to it. If one is not available locally, get on a plane and find one. When you've reached this level of excellence, you move into the arena of personal taste. If you choose to ignore this advice and your system has the resolving power, you cannot go wrong with the 18NS. In fact, if you don't need complex control functionality, you'll be in heaven with the darTZeel. I bet that for many, it will be a lifetime purchase. It is that rarest of breeds, a revolutionary state-of-the-art preamp that breaks new ground with its design, execution and performance. If you're in the market for a state-of-the-art preamp or just want to hear the results of one man's lifelong passion and brilliance, track one down and listen to it. Highly recommended. 
….. Mike Malinowksi
Inserting the NHB-18NS into my already excellent-sounding system was like being in the middle of an otherwise grand tropical vacation and suddenly having all the bugs disappear.
Michael Fremer - Stereophile

the darTZeel NHB-18NS is among a handful of the finest-sounding pieces of audio gear I have ever heard. Listening through it produced the same serenity I get every time at Avery Fisher Hall, just after the conductor's baton has gone down and the music has begun. if Hervé Delétraz wants to give me a long-term, semipermanent loan of the NHB-18NS, I'll take it.

With the introduction of the NHB-108 stereo amplifier, Swiss-based darTZeel quickly established a reputation for pristine, hand-built quality, fanciful industrial design, and elegant circuitry—all accompanied by a healthy jolt of sticker shock. (See John Marks' coverage in his September 2003 "Fifth Element" column, followed by Wes Phillips' full review in April 2005 .) The 100Wpc (into 8 ohms) NHB-108 costs more than US$18,000. A lot of change for not a lot of power, but the reviews were unanimous in praising the amp's exceptional sound quality. 

The boutique company's second offering, the battery-powered NHB-18NS preamplifier, exudes darTZeelness, including a price of US$23,250. Like the power amp's, the preamp's front and rear panels are finished in a dark gold that was a taste no visitor to my listening room managed to acquire. Not helping the Gold Acceptance Factor was the unusual retro-industrial red of the chassis, which was reminiscent of (take your pick): Radio City Music Hall before it was renovated, an 8mm projector from the 1940s, or an Erector set. Contrast the red and gold, add the two knobs' red LED backlighting and the three butterscotch indicator lights, and if it weren't a piece of electronics and didn't weigh 50 pounds, I could imagine finding one of these in Lauren Bacall's purse. But I ended up liking and understanding the NHB-18NS's warm, vivid color combination: The preamp looks like it sounds.

An interesting choice of features
While the NHB-18NS lacks some of the features found on microchip-driven preamps festooned with fluorescent screens, its functionality could hardly be called minimalist. That's good—a $23,250 preamplifier should pretty much be able to do everything but put the record on your turntable and lower the stylus into the groove. (By the way, NHB stands for "not heard before," NS for "no switches.")

The NHB-18NS features six inputs: five unbalanced RCA (one is for the built-in phono preamp) and one XLR. Four of the inputs also have selectable 50 ohm BNC Zeel jacks.1 There are six outputs: one unbalanced, one XLR, one unbalanced, a buffered tape Out, plus three 50 ohm BNC darT connectors for use with the NHB-108's 50 ohm BNC Zeel input.

According to the NHB-18NS's preliminary manual, the multiple BNC outputs are for biamping and triamping, using filters built into the preamp. All will eventually be described in detail in the manual's final edition, but basically, these are "rough" first-order filters designed to reduce IM distortion by separating and limiting the frequency ranges reaching the speaker drivers. They are not meant to replace speaker crossover networks.

A three-position toggle switch just below each unbalanced line-level input RCA jack provides 6dB of attenuation for high-output sources, or 50 ohms input impedance for future darTZeel source products. The XLR input has two toggle switches: the upper one lets you select an input impedance of 600 ohms for professional audio gear or 6dB of attenuation, and the lower offers three grounding possibilities for the XLR chassis jack: Floating, Chassis (100-ohm resistor to chassis), and the default position, Ground.

The front panel has an input-selector knob that darTZeel fancifully calls the Enjoyment Source, and a volume knob salaciously labeled Pleasure Control. Between the two knobs is not a button labeled Push-Up Bra, but the equally unlikely Power Nose. Surprisingly, the balance knob is labeled Balance. Not surprisingly, it's not your standard balance control: There's no change in balance until you've rotated the control ±5°. At full right, the right-channel level increases by 3.5dB, while the left decreases by 3.5dB, and vice versa at full left. This provides precise level adjustment while maintaining the overall volume level.

Two toggle switches mounted directly under the Power Nose offer controls for Mute/Home Theater Bypass and Mono-Stereo/Dimmer. A quick flick of the former mutes the system. Hold it down for about seven seconds and the Mute LED turns green, indicating that the selected input has bypassed the Pleasure Control and is set to 0dB gain, where it will remain until the next seven-second press. The other switch toggles between Stereo and Mono output; holding it down for more than five seconds switches off all lights and LEDs. You can also extinguish the illumination via the minimalist remote control (which is nicely milled of aluminum) by simultaneously pressing the volume Up and Down buttons. Other than volume, the remote offers a Mute button.

A small, unobtrusive-looking stainless-steel box containing the power supply/battery charger connects to the preamp's rear panel via an umbilical, and to your electric service. There are no AC transformers in the main chassis.

I'll spare you the various LED status indicators, except to say that they're logical and informative: Should the four batteries run down, the center LED glows red to tell you that the NHB-18NS has switched itself to AC mode. However, that's not likely to happen as long as you remember to turn the unit off after listening; a single charge is said to be good for well over 10 hours. I never did see that LED turn red, meaning that my review sample was never AC-powered during Enjoyment, and the batteries were charged when the NHB-18NS was turned off. (I usually need charging after Enjoyment.)

Unless its batteries are completely drained, the NHB-18NS automatically powers on in battery mode. Even if partially discharged, the unit will run on battery power; relays disconnect the AC input from the power supply when the NHB-18NS is powered on.

Using the Nose to achieve Pleasure and Enjoyment
The NHB-18NS preamp was ready to go about 10 seconds after I pressed Power Nose. Perhaps because it's battery-powered, the NHB-18NS seemed to require no warmup to achieve ultimate sound quality. However it sounded after three hours of listening was how it sounded as soon as it was powered up, or extremely close thereto.

Switching between Enjoyments—I mean sources—engages a mute circuit that avoids pops and clicks by inserting a half-second delay before the chosen Enjoyment begins providing it. The phono section requires eight seconds to engage when selected, but switching back to a line input takes only half a second. Because the inputs are indicated only by Roman numerals and can't be assigned names, you'll just have to remember what you connected where.
The proprietary volume, or Enjoyment, control uses no contacts, relays, switches, or silicon devices. DarTZeel isn't talking about its exact methodology, saying only that "some light is involved." Like all optical volume controls, this one keeps spinning as you turn it. The volume gradations were extremely fine—there are 192 of them in 0.5db steps, with a precision of "about plus or minus 0.2dB, closer to 0.1dB at typical listening levels." At no time did I ever wish for a volume level between two positions. If you turn the Enjoyment knob too quickly, it won't react, in order to prevent large, sudden, speaker-damaging increases in volume.

The built-in phono preamplifier's factory default settings are for moving-coil cartridges, 60dB gain, and 836 ohm loading. A 1nF cap is included to squelch incoming RFI from the cartridge. Owners who know how to use a soldering iron can set the phono gain between 30 and 66dB and adjust the loading via "solder pads." (How this is done will be spelled out in the forthcoming manual.) Moving-magnet cartridges can also be accommodated, though there are no capacitive loading options—according to designer Hervé Delétraz (darTZeel is an anagram of Delétraz), modern MM cartridges no longer require adjustable capacitive loading, and phono cables usually add the right amount. I doubt anyone buying an NHB-18NS will be using an MM cartridge—not that there's anything wrong with MMs.

The NHB-18NS functioned smoothly and without glitch throughout the entire review period. My only complaint was the remote-control receiver's narrow reception window. I had to point the remote directly at the preamp; even the slightest deviation from dead-on-axis resulted in no communication at all. Fortunately, the central LED glows green when the remote and receiver are communicating. DarTZeel is working to improve the remote's off-axis performance.

Circuitry, or lack thereof
Hervé Delétraz first showed me the NHB-18NS in prototype form at London's Heathrow Hi-Fi show in fall 2005. He removed the cover and ran me through many of the dual-mono design's elements, including the bank of four large batteries and 12 vertically mounted parallel circuit boards—one each for the six inputs per channel. The main board, which is mounted to the chassis bottom, accepts input signals via ribbon cables and connectors. Modern surface-mount technology is used throughout. There appeared to be nothing old-fashioned or retro about the circuit design, nor did there appear to be any unusual components, such as capacitors the size of toothpaste tubes. The NHB-18NS's interior build quality is commensurate with its exterior.

When Delétraz, who has a degree in electrical engineering, again summarized the design for me in preparation for this review, its unique, minimalist nature became more apparent. The NHB-18NS's fully dual-mono design extends to both the battery and AC power supplies, as well as to the signal and ground paths. It uses no global negative feedback, not even in the phono stage, and no op-amps in the signal path. The claimed bandwidths of 1Hz–1MHz, +0/–6dB, and 10Hz–100kHz, +0/–0.5dB, are ultrawide, for zero claimed phase shift.

"For the first time in all audio history," said Delétraz, "the signal path does not pass through any physical switch, relay, or even transistor switch." Instead, inputs are enabled or disabled using electro-optical analog components. Because there is no physical input switch or FET-based analog switch, there is no "diode effect," either electrical or chemical (electrovalence differential), to alter the signal, he explained in an e-mail.

All of the audio circuits are "directly scaled down" from the patented NHB-108 power amplifier, with minimal numbers of active components in the signal path, all of them discrete, bipolar transistors. The signal passes through only seven transistor junctions from input to output in the line stage, which provides 11dB of gain (5dB using the 50 ohm darTZeel connections).

The phono stage incorporates two gain circuits using eight discrete junctions in the signal path. RIAA equalization is passive and includes the fourth "Neumann" pole (3.18µs/50.048kHz) to ensure accurate high-frequency reproduction.

The chassis is CNC-fabricated from raw aluminum plates and billets, then hand-brushed and -anodized inside and out, then precision-adjusted with cogging pins, similar to watch construction (it's made in Switzerland, after all).

According to Hervé Delétraz, his goal was to create a preamplifier with maximum transparency, low noise, a subjective sensation of relaxation, and a coherence of rhythm and pacing resulting from, among other things, the "elimination of phase shifts at the frequency extremes."

Straight wire with gain?
Should a preamplifier be merely a traffic director, controlling the rate of signal flow and routing signals along chosen pathways while remaining neutral about what's passing through the pipeline? Or should it also impart a pleasing flavor to the proceedings?

These questions, long debated among audiophiles, are a waste of time, in my opinion. Anything inserted into the signal path will change the sound, even a passive volume control—especially if it's unbuffered. Those who seek some mythical "sonic purity" should probably give up audio and join a monastery.

Any audiophile who's bought a tubed preamplifier has decided to impart a particular sonic flavor to the proceedings. However, the same can be said of those who prefer solid-state preamplification. The conflicted choose hybrids of both technologies, such as my reference Musical Fidelity kWP. Whichever technology you choose, it should at least be quiet, dynamic, wideband, linear, and produce a low level of distortion. Both my listening and John Atkinson's measurements confirmed that the Musical Fidelity kWP, which isn't exactly inexpensive at $11,000, easily met those criteria (see Stereophile, December 2005), as did the three-box, $26,000 McIntosh C-1000, which I reviewed (and loved) for the August 2006 issue.

I haven't yet seen the NHB-18NS's measurements as I write this, but having listened for a few months, I don't doubt Delétraz's claim of quiet, dynamic, linear, wideband performance with low distortion (though the "less than 1% THD" spec isn't all that low). While 11dB isn't a great deal of gain, it proved more than sufficient when paired with any of the associated power amplifiers. No output impedance is specified for the unbalanced outputs, but based on my listening, especially comparing darTZeel's proprietary 50 ohm darT and Zeel connectors with standard single-ended types, it should measure sufficiently high to create no problems for most amplifiers.

Yet switching to the darTZeel NHB-18NS from the MF kWP produced profound sonic changes in my audio system, almost all of them much for the better, at least subjectively.

On first hearing, the darTZeel immediately revealed itself to be stunningly transparent, giving my Wilson Audio MAXX 2 speakers an electrostatic-like top end. Transient speed, resolution, and decay were nothing short of spectacular from day one, and that particular window on reality still retained its grip on my listening experience months later.

Shortly before I installed the NHB-18NS, an LP reissue of Clark Terry's Color Changes arrived (Candid/Pure Pleasure). Recorded in 1960, when Terry was a member of The Tonight Show's NBC Big Band, the album includes other NBC bandmates, such as drummer Ed Shaughnessy and pianist Tommy Flanagan, as well as veteran bassist Joe Benjamin, trombonist Jimmy Knepper, and French horn player Julius Watkins. The album, perhaps Terry's best, highlights Yusef Lateef's superb wind, horn, and oboe playing in Terry's harmonically charged, color-saturated arrangements. I played it often.
In fact, Color Changes was the first record I played through the NHB-18NS (still using the Manley Steelhead phono preamp), and the differences wrought by the darTZeel were major. In addition to the aforementioned transparency, I easily heard improvements in harmonic development, image delicacy, three-dimensionality—and, especially, overall coherence, as if everything was arriving on time as never before.

Clearly, Hervé Delétraz seemed to have met his goal of "maximum transparency...along with a subjective sensation of relaxation, and a coherence of rhythm and pacing." And how! The NHB-18NS defined and delineated the difference between serenity and boredom. It always produced the former, never the latter. I understand you're not supposed to feel serene while listening to the band Tool. The NHB-18NS overlaid the music with serenity, which was induced by the absence of unwanted sonic distractions such as those caused by phase shift.

I switched to orchestral music and again heard intoxicating sound that revealed both profound instrumental delicacy and retrieval of low-level instrumental and spatial detail, with back-of-the-stage reflections becoming particularly evident without unnatural spotlighting. Well-recorded massed strings possessed the appropriate delicacy yet clarity of attack I hear live, while brasses had an ideal proportion of burnish and bite. Female voices attained a new level of naturalness and purity that combined the midband warmth of tubes with the transient clarity and cleanness of attack of the best solid-state gear. Norah Jones whistles on one track of her new album, Not Too Late (Classic Records 200gm LP/CD, Blue Note 3 74516 2), superbly recorded on analog tape at 30ips; it sounded real through the NHB-18NS.

Often, delicacy, purity, and freedom from grit and grain can be attained only at the expense of high-frequency extension and resolution.The darTZeel managed to produce grain-free purity and improved extension, resolution, and especially transparency when compared to my reference kWP—or to anything else I've heard. The dual-mono design's soundstaging was appropriately expansive and exceptionally deep.

Did the NHB-18NS wimp out on hard rock? Hardly. Nor did it sugar-coat bright, hard recordings. If anything, it revealed ham-handed equalization and, thanks to its speed and resolution, laid bare pumping compressors and other forms of studio detritus—but somehow, even when the recording news was bad, the end result was pleasurable, especially because the darTZeel didn't add "edge enhancement," nor did it seem to soften transients, even if might have imparted a slight velvety finish to the final picture.

The preamp's bass performance was fully extended, texturally supple, and harmonically well developed, but perhaps lacked the tight-fisted control found with some of the big-box solid-state competition from Krell and Boulder—though it bettered almost all tube preamps I've heard in terms of control, definition, and extension.

The darTZeel's ability to express microdynamics surpassed that of any preamplifier I've heard. Perhaps the only area where the Musical Fidelity kWP beat it was in terms of macrodynamic scaling, where, thanks to the kWP's amplifier-like output capabilities and overbuilt power supply, it may scale somewhat greater heights than the darTZeel.

The changes wrought by the darTZeel in my system were so profound that I had to wonder if it was adding colorations rather than subtracting the processing errors made by my reference. Whichever, I'm not sure it matters. Whatever the darTZeel was doing or not doing, it made recorded music, analog and digital, sound much closer to live, especially texturally and harmonically. It did so with MF's big kW amps driving the Wilson MAXX 2s, the Peak Consult El Diablos, or the Focal Electra 1037s (currently under review). It was equally convincing driving a pair of Ayre Acoustics MX-R monoblocks—and, of course, darTZeel's own NHB-108, via the proprietary 50 ohm link.

The built-in phono stage
After weeks of living with the Manley Steelhead phono preamp patched into the darTZeel, it was time to check out the NHB-18NS's own phono stage. It brought yet another level of transparency, though two stages of darTZeel circuitry in series did bring a slight diminution in macrodynamic scaling.

A case could be made that the NHB-18NS's phono stage slightly softened transients, though I could also make a case for it producing more natural, less edgy transients as well. That a built-in phono preamp could duel to a draw with an outboard one costing more than US$7000 is praise enough, though if you like to play around with cartridge loading, the darTZeel phono stage probably won't satisfy you. However, every time I switched back to it from the Steelhead, music sounded more natural and less "reproduced," despite the slight loss of dynamic contrasts (and the Steelhead is not the last word in terms of dynamic contrasts). The darTZeel's phono section deserves more space, but I'm running out of it.

Inserting the NHB-18NS into my already excellent-sounding system was like being in the middle of an otherwise grand tropical vacation and suddenly having all the bugs disappear. However, whether any part of the darTZeel's singular performance strikes you as oh-so-right or just too much will in part be determined by the associated gear, especially if your cables suffer from clogged sonic arteries, or your phono cartridge is ultra-lush.........

No matter how good a piece of gear, it remains one ingredient in a recipe. That said, whether its minimalist circuitry provides purity by subtracting unwanted junk or by adding pleasing colorations, the darTZeel NHB-18NS is among a handful of the finest-sounding pieces of audio gear I have ever heard. Listening through it produced the same serenity I get every time at Avery Fisher Hall, just after the conductor's baton has gone down and the music has begun.

Reviewers can't seem to win. No sooner do I make an issue of actually having bought and owning the major building blocks of my reviewing system than I hear from a manufacturer and importer complaining that, when a reviewer buys his system, he's so "invested" in it that a competing component is less likely to get a fair review. In that manufacturer's opinion, long-term manufacturer loans to reviewers are actually preferable.

That I don't agree should be proven by my conclusion that the darTZeel NHB-18NS smokes the expensive preamp in which I've already invested. But just to keep that faction happy, if Hervé Delétraz wants to give me a long-term, semipermanent loan of the NHB-18NS, I'll take it.

Description: Solid-state preamplifier.
Inputs: four unbalanced line-level (switchable between RCA and 50 ohm Zeel BNC), one unbalanced phono (RCA), one balanced (XLR).
Outputs: one unbalanced (RCA), one balanced (XLR), one buffered Tape Out (RCA), three 50 ohm darT (BNC).
Frequency responses (depend on measurement method): 1Hz–1MHz , +0/–6dB; 10Hz–100kHz, +0/–0.5dB; 20Hz–50kHz, ±0.5dB (XLR inputs & outputs).
THD: <1%, 7Hz–77kHz.
Signal/Noise Ratio: 100dB (A) line level; >70dB phono.
Risetime: <0.8µs.
Slew rate: >88V/µs peak–peak.
Crosstalk: below –90dB, 20Hz–20kHz.

Should such heady sums be within your reach, you will own a system to rank with the very finest that money can buy.

Make no mistake: the NHB-18NS pre-amplifier is exactly the mate for which the NHB-108 Model One power amp has been waiting. They complement each other perfectly, delivering a one-two punch that will knock a hole in the high-end solid-state sector. Admittedly, with a combined price befitting a decent car, you should be getting more than mere amplification, and you do: silky, seductive sound with power to spare. I suppose - were we to follow a car analogy - you could liken this in every way to a modern Bentley: sophisticated, capable of cosseting the owner, yet able to play the hooligan when the pedal is floored. Maybe labelling the volume rotary 'Pleasure Control' wasn't so daft after all.

Extended review:
It's been made clear to me more than once just how privileged I am to receive the actual production version of the long-awaited darTZeel NHB-18NS pre-amplifier for review before anyone else. However obscure Switzerland's darTZeel may seem, it's now a global player in the extreme high end. And the pressure for the scoop review of their first pre-amp ramped up by a factor of 10 immediately after their NHB-108 power amplifier won a brace of awards from our friends across the Pond at Stereophile.
According to the distributor, there was a queue of reviewers dying to get their hands on it, they had to fend them off with fears of the sorts of repercussions that follow bruised egos, why Kessler?, yadayadayada. So I suppose my offer to sleep with Serge and Her- no, that's a lie: I earned the privilege because I bothered to fly to Geneva, hang out with the pair, learn about the product and prove my worthiness. The latter might even be due to sharing a common taste in music with Hervé Delétraz.
Must've worked, because I've just spent a couple of weeks with the little beauty. No kidding: I do feel privileged. Yup, it's that good. And it' so fresh that it doesn't even have a blank name plaque in the upper right-hand corner; that awaits the engraving of the name of the eventual owner. And having heard the power amp on numerous occasions, I can confirm that - unlike other situations where one part of a pre/power package preceded another, and Part 2 was a let-down - the darTZeel boys followed their debut with a perfect sequel. Think Godfather 2, The Two Towers or Attack of the Clones. Well, maybe not the Attack of the Clones. But you get the drift.
As with the power amplifier, darTZeel opted for direct paths and 'heightened minimalism' if such a phrase isn't borderline oxymoronic. As Hervé put it, 'Our dedicated circuits are reduced to their most basic form. As before, there is no application of any overall negative feedback. Because of this approach, the delicate, small audio signals amplified by the NHB-18NS only pass through seven silicon junctions, from input to output. And that includes the 13dB full discrete gain stage. And for the phono stage, we only add six junctions, for a maximum additional boost of 66dB, or 77dB in total.' Their minimalist circuits are currently 'patent pending.'
Despite the company's designers suffering an affection for the hideously coloured Rehdéko loudspeakers, they insist that the darTZeel goal is for untrammelled, pure and open sound. Amplifying the low level signals are discrete devices, or matched transistors embedded in dedicated integrated circuits. Hervé again: 'No operational amplifiers are used in the entire signal path. As in the NHB-108, all components used in the NHB-18NS preamplifier, with no exceptions whatsoever, are based on the finest products being produced by leading-edge industries at the present moment.'
This is where you start to get whiffs of the Swissness, which requires a brief aside about the 'Made in Switzerland' philosophy. First devised, adopted and safely guarded by the watch industry, that coveted identification of birthright is as closely protected as French wine's or cheese's 'apellation contrôlée', or olive oil's IOOC. darTZeel uses as many Swiss suppliers as possible, partly because the company jingoistically (but rightly) believes that the Swiss are the best at manufacturing anything made from metals, including electronic components, and partly so that darTZeel could become the only audio company to earn the coveted Swiss Label Certificat, attesting to its Helvetian purity.
Those of you who don't share, say, my obsession with Alpa cameras, watches and Nagra tape decks might wonder about the fuss, but - away from ultra-nationalistic Germans and Brits who refuse to believe that anyone could make things as well as they could - any form of proof that your wares are as Swiss as William Tell is akin to the Good Housekeeping Seal of Approval and an Appointment by the Queen all rolled into one.
So darTZeel has taken the best ingredients, and formulated a topology that includes the following strictures:
There are absolutely no contact or switches nor relay of any kind for source selection, all in the interests of absolute transparency. darTZeel prefers, instead of routing signals through a selector box, to provide each input with its own dedicated gain stage, enabled or disabled according to the user's choice. The signal is then directly routed to the volume control module.
In the NHB-18NS, the volume control module completely avoids the use of any potentiometer, stepped attenuator or analogue switch array in the signal path. According to Hervé, 'The sound signal is attenuated in a fully passive way, within a continuous range of close to 96dB in 192 steps of 0.5dB, in full analogue mode, without the use of any VCA or other active component.
'Both of these breakthroughs constitute a big step in the right direction: no harm to the signal. As mentioned above, this new design is patent pending. As soon as the patents are confirmed, darTZeel will be pleased to describe in detail how such signal treatment is possible.'  More Swissness: they adore secrecy. Just ask anyone who banks with them.
Further in keeping with the NHB-108 power amplifier, the NHB-18NS uses only small amounts of local negative feedback at the inputs, with one small, symmetrical loop of local negative feedback in the voltage gain stages. The output stages are open loop, and free of all negative feedback. 
Within the 440x170x335mm (WHD) chassis is a modular frame, with every stage on a subassembly more like a computer or multi-channel A/V amp than a stereo preamp. Because of this, the unit might one day be customisable to a degree; at present, though, its modularity shows that the unit was designed from the outset to resist obsolescence.
Unusually, the company employs its own preferred, proprietary 50-ohm 'darT' outputs and 'Zeel' inputs with BNC connectors, alongside more conventional connections. As shipped and reviewed, the unit features a mix of six inputs covering phono, RCA/BNC and balanced XLR. As standard, these include a phono MM/MC input with gain from 30-66dB, a single 'full-floating' XLR input and four RCA/BNC 50 ohm Zeel inputs. Outputs consist of one XLR full floating output, three BNC 50 ohm darT outputs, ready for tri-amping, with optional built-in passive filters, a pair of RCA outputs and a pair of fixed RCA record outputs.
Completing the package, and for many the most important part, is a feature shared by darTZeel's compatriots at Nagra: a battery power supply. Because the NHB-18NS is an 'authentic dual mono preamplifier, from input to output, with separate grounds for left and right channels,' each channel is battery-powered by its own battery bank, offering up to 15 hours of playing time on a full charge. Every input and output is treated to a 'very sophisticated, regulated and dedicated supply, ensuring the lowest power supply impedance possible.' And it's basically set-and-forget: automatic functioning allows full battery operation when listening, with the charging mode activated when the preamp is switched off. As Hervé puts it, 'Hum is gone forever, and there is no need to worry about knowing if batteries need to be charged or not.'
'Deliciously simple' described the front panel: source and volume rotaries marked 'Enjoyment Source' and 'Pleasure Control', an illuminated power on button called the 'Power Nose' (examples, I suppose, of Swiss humour), mono/stereo and mute toggles and a rotary balance which lowers one channel by up to 3.5dB while raising the other by up to 3.5dB. The back, on the other hand, is jam-packed. It contains all of the aforementioned input/output combinations and a multi-pin input to accept an umbilical from the outboard charger, along with earth tags for the phono section, toggles to apply 6dB of attenuation on certain inputs, and other toggles to defeat earthing in case of loops.
Other niceties include a beautifully-machined remote control for operating the volume; a home theatre bypass mode; multi-coloured LEDs to indicate battery status, charging modes, stereo mode, mono mode, mute, normal, etc.; and useful handles front and rear. The fit and finish are utterly and undeniably beyond criticism. Indeed, the only area one might possibly object to is the choice of gold front panel and red cover. It is, simply put, so frikkin' ugly that even a chav would find it objectionable.
But that's irrelevant. Within seconds of switching on, after allowing it to charge up fully, it was blatantly obvious that the darTZeel NHB-18NS goes straight to the head of the class. What we have here is one of those juggling acts performed only by the masters, that heady mix of delicacy and control, sheer musicality tempering almost clinical retrieval of detail, massive scale with no masking of the softest notes. And given its purely solid-state, Franco-Teutonic DNA, the shock is as great as hearing a German tell a joke. One that's actually funny.
I wish there were a way to provide a test CD that demonstrates when everything falls into place. It would include a recording that's 95 percent 'there', followed by the same again at 100 percent. Every pursuit has it, whether finding the perfect swing in golf, finding 'the line' on a race circuit, focussing a lens to perfection, burning in just the right amount of crunch on a crème brulée. The darTZeel does this over and over and over again. Even its phono stage, as set at the factory for median value m-c cartridges, obviates the need to look further.
Everything about the sound is carefully considered, of a whole, and in perfect proportion. From orchestral to unplugged soloist and every point in between - new, old, mono, stereo, digital, analogue - the darTZeel behaved with the kind of consistency that shrieks pedigree. It simply doesn't put a foot wrong, and even worst-case scenarios - CD transfers of 50s mono vocal discs - failed to reveal shortcomings. This pre-amp treats vocals, male or female, single or massed, with such utter respect that the sheer realism renders other systems artificial-sounding.
That stalwart, Keb' Mo', provided both melody and texture that tax most solid-state set-ups, which can never seem to get his rasp just so. They seem to amplify only the harsher elements of it, belying the warmth. Not so the darTZeel: it presented him front-and-centre, tall and noble, the voice a personal command performance, the guitar twanging for real.
Trying actively to upset the darTZeel revealed only one caveat: so clean is the sound that you may wish to play it louder than you might normally do, and I did manage to drive the matching power amp into clipping (as evinced by the LEDs). Even then, the clues were stern rather than shocking, and it never sounded like the system was about to implode. You'll be delighted to know that, wherever you dial the 'pleasure control', the scale remains consistent. You'd have to go out of your way to get bad sounds from this. Like hooking up Rehdékos.
Then there's the entry fee. Even before you consider the NHB18NS pre-amp at NZ$47,000, you really must consider its sibling, the NHB108B Power Amp, at an equally disturbing NZ$42,000. Should such heady sums be within your reach, you will own a system to rank with the very finest that money can buy. And a mystery, too, will be solved. For those of you who have pondered for decades how the world's premier jazz festival ended up on the shores of a Swiss lake, wonder no more. Montreux: maintenant tout est clair.
Make no mistake: the NHB-18NS pre-amplifier is exactly the mate for which the NHB-108 Model One power amp has been waiting. They complement each other perfectly, delivering a one-two punch that will knock a hole in the high-end solid-state sector. Admittedly, with a combined price befitting a decent car, you should be getting more than mere amplification, and you do: silky, seductive sound with power to spare. I suppose - were we to follow a car analogy - you could liken this in every way to a modern Bentley: sophisticated, capable of cosseting the owner, yet able to play the hooligan when the pedal is floored. Maybe labelling the volume rotary 'Pleasure Control' wasn't so daft after all.
The darTZeel is very close to being my ideal pre-amplifier;
Chris Binns

As one would expect of a high-end product of this calibre, it ticks all the right hi-fi boxes, but also makes the important step forward that ultimately cuts the ties that hold so many products earthbound when it comes to letting the music flow. And that, as I suggested earlier, is more important in a pre-amp than any other component in the system. The NHB 18NS is a highly desirable product, and one of the very few that could successfully fill the void left by the Ayre K-1xe, a design that already rearranged my views on pre-amplifiers.

Extended review:
Of all of the components that make up a hi-fi system, experience shows that it is the pre-amplifier that presents the biggest enigma. The task it has to perform is, in theory, pretty straightforward; directing the signal from the desired source component and controlling the volume. Compared to the process of extracting information from the reflective surface of a CD or the groove of an LP, or driving massive amounts of power into a loudspeaker whose job consists of converting electricity back into recognisable audio, it should be a walk in the park. Its not even as if there is any gain needed, as the output from an average CD player is more than enough to drive most power amplifiers into clipping. Hence passives, although in the real world, considerations such as input/output impedance and the capacitance of the cables hinder the attainable performance, while active circuitry provides a degree of isolation and stability against such effects.
Why then, am I so often forced to conclude that the pre-amplifier is the defining component of a systems ultimate performance. And, while the limitations of a poor source component or compromised power amp/ loudspeaker combination are relatively easy to identify, the pre-amp often seems to be a constriction or compromise to sound quality that manifests itself in a far more subtle way. Of all audio components, the pre is the one that we expect to be the most sonically pure and devoid of character, adding nothing while acting as the ‘gateway’ for the system that everything else connects to. And the truth is that for all the interesting and highly competent audio equipment I have auditioned in a system at home, the number of truly great pre-amps that have left a lasting impression can be counted on the fingers of one hand. The NHB 108 power amplifier was the first product to appear from Swiss based daRTzeel. A 100 Watt per channel design that was the embodiment of simple, elegant and beautifully symmetrical circuitry, it had a build quality and attention to detail second to none. It also sounded staggeringly good. I was therefore only too happy to have it back while auditioning the 18NS pre-amp, which is built as you might expect, in much the same fashion. Imagine Swiss watch precision applied to virtually every aspect and you begin to get the picture; attention to detail and refinement is the order of the day. Aesthetically the daRTzeel is quite conventional in its shape and mechanical construction, but the metalwork is finished in an industrial red anodising with a mustard gold front panel (which incidentally is much darker than the power amplifier) and I guess this is a look that you will either love or hate – me, I’m making no comment. Further enhancing the ‘glitz’ factor is the gold plated nameplate that you send back to the manufacturer to have engraved with the serial number and your name once you have purchased the unit. Front panel controls consist of a power button, small toggles for mute and mono (hurrah!) and two rotary controls for input selection and volume that are labelled ‘Enjoyment Source’ and ‘Pleasure Control’. A sense of humour lurking under the serious exterior?
Internal construction is about as good as it gets, using selected components and no less than twelve input boards on which the connectors in one of the neatest Finally, three multi coloured Led indicators indicate the status and operating conditions of the pre amplifier. The 18NS has four single-ended line-inputs together with one balanced; the RCA’s are duplicated by (darTZeel’s proprietary) 50 Ohm BNC’s and there is a phono input; yep, the darTZeel has a fully fledged phono-stage on board, a trend that seems to be returning. Outputs consist of the usual fixed level tape, balanced and RCA options, augmented by three separately buffered BNC’s specifically for the 108 power amp (the instruction manual talks of incorporating filters for bi or tri-amping at a future stage).
The electronic design has a number of interesting aspects and some shared philosophy with the power amplifier. Thus the circuitry employs a simple, symmetrical configuration utilising discrete components (rather than op-amps) where the signal passes through only six transistors in the main gain stage. This delivers an impressively wide bandwidth, claimed to be within 1dB from 1Hz to 1MHz, with no overall feedback applied. Each input has its own dedicated gain stage, which remains permanently connected and is activated when required, thus avoiding any kind of switching in the signal path. Likewise, there is no potentiometer or resistor network in line with the audio, volume control being by passive attenuation governed by a dedicated processor via analogue optical couplers, offering 192 steps in increments of 0.5dB. This leaves the volume knob whirling like a dervish to make any ground, while the remote rather over compensates with sudden lurches up or down. Acceptance angle is narrow but otherwise it is a simple, tactile handset (unlike so many others). For once the balance control is subtle in action, rather than swinging wildly left and right. The phono-stage follows similar design criteria to the linestage, utilising discrete components to provide 60 db of gain, although both this and the loading are internally adjustable using a soldering iron; good for sound, bad for convenience.
The darTZeel comes with a separate power supply housed in a small, unobtrusive stainless steel box, although this actually functions as a charger for the 18NS’ onboard batteries. I will confess to initial scepticism; previous experience (now many years ago) with various designs involving re-chargeable Ni-Cads led me to conclude that the complications of using battery power were not worth the lack of reliability and frustration that went with it – not to mention smoke and blown drive units. But things have changed; battery technology has moved on in leaps and bounds over the last few years due to our insatiable demand for mobile technology, and the state of the mains supply is considerably worse, partly due to the rise of switch mode power supplies that are now literally everywhere. The prospect of completely isolating the audio circuitry is now more attractive than ever. Which is exactly what the darTZeel does, once the power switch is activated, relays disconnect the power supply from the internal batteries, which then deliver up to twelve hours listening in this mode. When switched off the unit charges the batteries, and in the event of them being completely flat the 18 will run, with slightly diminished performance, using the mains supply. Not that I was able to investigate this, as a testimony to the effectiveness of the power supply management this was a situation that never occurred, and as with all other aspects of the 18’s operation it performed seamlessly throughout the review. For those of us used to leaving gear powered up, it’s a new discipline having to remember to turn it off after a session, but tellingly I could hear very little difference in quality between a cold start and a few hours of use.
It could well be the combination of a number of different but related attributes, but I had an immediate sense of a very clean, transparent presentation with no detectable fuzz or smearing to cloud the leading edges and subsequent body of sounds. And a wealth of detail; not of the “I’ve played this track for years and never heard the drummer fart variety” but more constructive information on note shape and textural qualities that enrich the music rather than distract from it. But I think the most persuasive aspect of the darTZeel has to do with wide bandwidth coherence. I’m convinced that the timing verses frequency issues are an important part of breaking down psycho – acoustic barriers that allow music a more direct connection to the relevant parts of the brain. In other words, the better a piece of equipment is at doing this, the more relaxed I am listening to it and as a consequence less aware of the hi-fi. This particular aspect of performance was highlighted by the Quad 2805 electrostatics, which were far more willing to do the spooky holographic image trick with the darTZeel in the system, often completely disappearing.
While the character of the 18NS was essentially neutral, I was always conscious of a very slight sense of warmth to the sound; not in an indistinct, hazy valve-like way but more akin to a slight hint of ‘richness’ that accompanied the music, contributing to a tactile sense of body and substance with natural instruments and voices. Slightly more apparent using the phono-stage, reproduction from vinyl was supremely confident and assured in a way that had me wishing I never had to play CDs again. It majored on flow and involvement over laid bare, concise (and possibly clinical) retrieval of detail that one or two other high-end phono stages are better at.
The darTZeel power amplifier allowed me to examine differences between the pre-amp’s three output options. Designer Herve Deletraz has some passionate and distinctive views on cables and signal transmission; hence the unusual 50 Ohm BNC sockets and the matching cables supplied with the unit. Not unexpectedly, these provided the best results with an obvious synergy between the two units: balanced operation via the XLRs seemed sluggish and indistinct by comparison while single-ended connection was considerably better, but still falling short of the custom interface in terms of speed and focus. Using the darTZeel pre and power together proved an awesome combination, but I occasionally felt that it was almost too perfect: perhaps a slightly sickly sweetness that could occasionally have you yearning for a bit of aggression or rudeness with certain music. Can you have too much of a good thing? Maybe, but then both the Quads and the Spendor SP100R are on the polite side. DarTZeel employ Rhedeko loudspeakers for product development – which constitute quite a contrast…
Ironically, sometimes the better a product is the less there is to write about it, and after a couple of months spent listening to the darTZeel I am still struggling to define certain aspects of its performance. As one would expect of a high-end product of this calibre, it ticks all the right hi-fi boxes, but also makes the important step forward that ultimately cuts the ties that hold so many products earthbound when it comes to letting the music flow. And that, as I suggested earlier, is more important in a pre-amp than any other component in the system. The NHB 18NS is a highly desirable product, and one of the very few that could successfully fill the void left by the Ayre K-1xe, a design that already rearranged my views on pre-amplifiers. The darTZeel is very close to being my ideal pre-amplifier; one that, like well behaved children, is seen but never heard.
……Chris Binns
Hervé Delétraz Interview with Mike Malinowksi
Mike Malinowksi

Recently I had the remarkable opportunity to combine business with pleasure during a trip to Europe and spend a day meeting with Hervé and Serge in Geneva. This proved to be one of the highlights of my trip. Having never been to Switzerland, I had no idea what to expect. Regardless of your education and experience, we are all saddled with preconceived notions. Mine was the vision of the Swiss as cool, polite and somewhat aloof. Boy was I wrong. Hervé and Serge were warm, open, down to earth and both gifted with a great sense of humor. They welcomed me into their homes and lab and through this interview, offered an insight into their wonderful driving obsession. The conversation bounced between history and technical theory and mixed with some refreshing honesty as you will see. During my various meetings and discussions with Hervé, a single word stood out prominently in my notes: "passion," defined by Webster as intense, driving, overmastering feeling or conviction. That certainly defines Hervé.

Q: Tell us a little of your background and your beginnings in audio.
A: In 1984, I received my diploma in engineering and began to design a digital amp. I wanted to make an amplifier of the simplest possible design. I built a prototype amplifier in 1999.
Q: A digital amp?
A: No. It was the darTZeel Model 0, a big monster - big case but pretty empty inside. I designed it for myself and friends, not as a commercial product. The problem was that my friends did not want to give me back the prototype because of the sound. My friends encouraged me to make a series because the sound of the prototype was that good. So I was encouraged to continue.
Q: (to Serge) How long have you and Hervé worked together?
A: I have been part of darTZeel from the beginning, when the first circuit board exploded as I turned on the Variac. Today, I handle sales and marketing and manage other areas. Hervé and I are a good complement. I have total trust in his design genius. On the marketing side, you have to focus all the ideas and imagination to make a product successful. The original amp was built for Hervé personally. He wanted the best for his system. The only purpose was for it to be loved by a listener but eventually it became Hervé's job and he involved me in this adventure. When you translate that to a commercial product, priorities change. You cannot wait 16 more years for a new product. The challenge was, how do you translate the passion to a commercially successful product?
Q: What was so special about the prototype?
A: The problem was in fact that I was not worried about harmonic distortion because in instruments, you already have a lot of natural harmonics. Most musical instruments have 20 or 30 percent natural harmonics, so limiting harmonic distortion is not necessary. If you have only 1 percent harmonic distortion compared to 20 or 30 percent of natural harmonics, you don't hear a difference. So my quest for this amp was more for speed, less phase shift and simplicity of the circuit. The new 108 has only six silicon junctions from input to output for the signal path. There is no feedback at all from the output, the schematic is very simple - but it is not simple to make it work properly. I tried for years and finally developed the circuits of the 108 which are patented worldwide because they are, in fact, new designs. No one had a design like this although some might look similar. Now the story of the darTZeel company begins. I showed the amp at the New York 2000 HE Show for the first time. At that time, I had one distributor, Jonathan Tinn in the United States. In a short time, we were distributed worldwide, including Europe, Japan and Asia. It was not easy building this network with one product because the preamp was released much later than anticipated.
Q: What about the unusual name?
A: (Serge) The name is an anagram of Hervé's last name, Delétraz (darTZeel). In addition to the meaning, the name has visual impact and creates the image of technology and circuitry.
Q: With the growth of home theater and the decline of two-channel systems, why pursue such a small niche market?
A: We have two ears, two eyes and I think we can pretty well reproduce music with only two speakers. At a concert, the musicians are in front of you, not behind you. You can have the sound reflections which give a rear sound without the need for additional speakers. I do not like rooms with too much absorption.
(Serge) I have known Hervé since we were children because we are cousins. So I can add an explanation. I think that home cinema is associated with TV or visual images and both Hervé and I are aficionados of sound and music. Home theater was originally dedicated to the image first. It is only recently that theater sound is being addressed by the high end audio companies. Our goal is to produce the ultimate in music reproduction. I won't say that we will never make a multi-channel system but not today. The sound tracks in movies are at times much exaggerated. However, with well reproduced music, you just close your eyes and you can feel the experience. For Hervé and me, it is all about the music.
Q: Do you design for a particular sound?
A: No! Generally you can associate a sound with a brand. Designers make a family sound but that was not my goal. My goal was to accurately reproduce the musical signal as close as possible. I do not think about making it sound like tubes or transistors. I just wanted to make a good amplifier.
Q: Describe your design process.
A: I design first using a computer simulation to make sure that the electronic design works. We then build a bread board prototype. We listen intensely and after we are satisfied, we move to a circuit board and listen again. Listening is the most important part in the design process.
Q: Your speakers are unusual. Tell me about them.
A: I love these speakers because they are very unforgiving. They are by Rehdéko, a French brand. It does not exist any more. Its original designer was a real magician. He died since and I really miss him. I know his son and the father who left instructions that after his death, the speakers would stop production. There were many secrets in the manufacturing of these speakers, almost like a Stradivarius violin. The speaker membrane for example is treated with many different varnishes. Many of the varnishes are aged for maybe seven years before being applied. The result is that the speaker membrane is more rigid than Kevlar. The speaker is very fast and slightly aggressive in the midrange. It is amazing. The designer, a musician, wanted to reproduce instruments in the most natural way. So when you hear a trumpet or a saxophone live, it is very aggressive - these speakers are exactly the same. It is not hi-fi sounding, but very musical. They are highly efficient, about 106dB for 1 watt at 8 ohms.
Q: Are these the speakers used for your design and voicing?
A: They help a lot in the design because if you have a tiny problem in the circuit, you can easily hear it immediately. They are great design tools, but ultimately, they sound like music.
Q: What kind of music do you listen to?
A: Only a small part is classical - I'm too young. But seriously, I like all types, including jazz and rock – old rock groups like Genesis, Pink Floyd, Jethro Tull and the Beatles. I appreciate classical, but it is much more difficult to reproduce accurately. Even with the best system in the world, it is extremely difficult. One hundred musicians playing in natural space, 20 to 30 meters from the audience at full volume is difficult to capture on a recording. Jazz is easier to reproduce. Three, four or five musicians could actually fit into the room so with jazz, you are closer to reality.
Q: Once you get to the basic sound you want, how do you tweak the design to meet your goals?
A: Again, we do not particularly tailor the sound to any style. On the power amp, we could tailor the sound. We could, for example, make it rounder. The amp is extremely fast. If we made it a bit slower, you could make it sound more 'tuby'. Depending on the input impedance, you could round the bass but it is not my aim to tailor the sound. I look for accuracy. I will tweak the value of some components however, a higher or lower resistor, for example, to add a bit more current for better speed. The relationship between technique and sound is very close because a good measuring amplifier can often sound bad, but the contrary is more difficult. It is difficult to have an amp that measures poorly and has good sound. There are some, maybe, but it is not easy.
Q: What about tube amps, some measure poorly but are very musical.
A: Some tube amps, yes, but I think that with tube amps, if you keep them for two or ten years, you could end up with fatigue because the sound becomes too polite, too round, too smooth. With the 108, we noticed the opposite effect; the longer a customer listened, the more they liked it.
Q: Discuss the long break-in period for your amps
A: Reviewers have written that the amp needs a lot of burn in to make real music. Agreed. But I also believe that the listener adjusts to the burn in.
(Serge) I think both the equipment and the listener adjust, especially with the darTZeel. The sound presentation with the darTZeel amp is a bit different than other pieces and you might need some time to get adjusted.
Q: How does the circuit design of the new preamp compare to the 108 amp?
A: The circuit design of the preamp, phono section and amp use the same patented design. In fact, the design can be used for any circuit - microphone, preamp, phono or power amp. The schematics are the same, but of course, we don't use the same devices. The amp uses power devices and the preamp, small devices - transistors. We use very low noise matched transistors and there are no op-amps in the signal path.
Q: Your designs focus on eliminating what you call 'temporal' distortion. You indicate this as the most audible type of distortion.
A: Temporal distortion occurs when you have phase shift on the bottom or the top. Reviewers might measure the square wave response of high frequencies. I've never seen a square wave response of a very low frequency. Normally an amp begins to show measurements at 100Hz. To have the plateau tilting indicates phase shift. An amp going down to 10 or 20Hz might have an excellent rise time but the plateau is tilted.
Q: Is your circuit wide band?
A:The frequency response extends from a few Millihertz. We don't have full DC from input to output because if you have DC at the input, you could have trouble. I have a coupling capacitor but we go very low. So the phase response is very good, even at 20Hz you have excellent square waves. You can hear it! The bass is much more precise. It might appear to be a little lean but that is because it is so precise and so fast. The duration is shorter so it might appear less but it is very clean.
(Serge) People are often used to boomy bass that shakes the room. If you critically listen to the bass driven by a darTZeel, you will hear that it goes very deep but with none of the resonant effects because it is exceptionally fast. Bass with other pieces produces monotonic sound. Our circuit design allows you to clearly hear the individual chords. You will hear far more bass detail with darTZeel.
Q: Therefore one of the design secrets to the darTZeel circuit is the square wave response minimizing phase shift?
A: Ideally, the amplifying circuit should go 10 times lower and 10 times higher than the audio band to have correct phase shift. Our circuits go 50 times lower and 50 times higher. Square waves are a very helpful design tool. You can see a lot of things. At 20Hz we are quasi flat; the phase shift is less than one degree at 20Hz. In the high frequency, we extend to about one megahertz - 50 times more than 20 kilohertz to attain about one degree of phase shift at 20 kilohertz.
Q: And the effect of this on the sound?
A: In the audio spectrum you are free of any temporal distortion.
Q: There are many amps with wide bandwidth. Some solid state amplifiers with very wide bandwidth such as Spectral and Halcro do not sound anything like your designs. Why?
A: Normally, when you want to reach very high in frequency, you need to use feedback. This, in my opinion, is the holy grail of amplifier design - overcoming the dilemma of high bandwidth requiring feedback and low feedback designs producing low bandwidth. This was the struggle of my design. How do you make a high-bandwidth no-global-feedback design work? The only feedback we use is a small local symmetrical feedback loop for the voltage gain. There is no feedback at all at the output or input. It is extraordinarily difficult to make this circuit work properly so to answer your question, other designers use some type of feedback to achieve bandwidth. I do not and hence the amps 'sound' very different. Also, I use only one pair of transistors as output devices. When you parallel a lot of output devices, you will have fuzziness and you will lose focus.
Q: With the small number of output transistors, how do you handle heat dissipation and stress on these output devices?
A: Thermal stress with only two output devices requires a very sophisticated monitoring circuit -- kept outside the signal path -- which can sense actual power dissipated in the devices. The NHB-108 is the only amp in the world to offer 100 wpc (and much more under 4 ohms) while other amps with a single pair usually offer 50 watts at best. Each output device amplifies a slice of the music and the signal might not arrive at the exact same time from all of the transistors, even if they used matched transistors. Two or three pairs can give good sound, but with more than that, it is very difficult to do. The best sound is with one pair. In our future monoblocks we will use two pairs for additional power but to do this I will have to redesign the schematic.
Q: A scoop? Are monoblocks in the works?
A: No, not currently, but they will be in the future. I envision a 300-watt amp but the challenge to keep the same sound will not be easy.
Q: Since the circuit is similar for the preamp, I assume the design goals were also similar.
A: When we started to design the preamp, Serge and I decided that the preamp would be the ideal companion to the amplifier. It took time to scale down the amplifying circuits for the preamp. Also, the amp uses no switches, relays or fuses in the signal path. For a preamp, this is much more difficult to implement. You have inputs. How do you implement them without switching? Yet we did it. All of the inputs are selected without switches or relays.
Q: Therefore, each input has its own gain circuit?
A: No, although we have a circuit card for each input. We turn on the card when we want to play that input - all without switching. In fact, we apply power to the card using a proprietary light system. The idea was to use light to energize components and with this approach, we can select inputs without the degrading effect of switches or relays. The preamp is completely dual mono. We have two batteries per channel. The grounds are fully separated from left to right and from the chassis. It is essentially two machines in one. The volume controls do use potentiometers for convenience but the signal does not go through it. We do use a resistor ladder, but not in a conventional way.
Q: What is wrong with conventional volume controls?
A: You lose something. I use a system that varies resistance with light. However, until all the patents are in place, I would prefer not to specify the details.
Q: Visually, the preamp's internal designs look more like a PC than a traditional audio component.
A: It is similar to a computer. Each input has a board but without slots because I don't like contacts. The sound connections for each card are hard-wired. The cards contain the proprietary light switching circuitry which enables or disables the specific input. As with the computer analogy, each card is connected in parallel to the motherboard. There is also one dedicated phono board per channel. We use small buffers with four transistors, the topology being the same as our amp - both sharing essentially the same circuit design.
(Serge) The volume control is a special design that has no tracking error. The worst case is no more than a 0.2dB difference, even better than Levinson's laser trend volume control. In its useful range, we have about .1dB of difference. Again, this was done with standard components, not exotic parts for long term maintenance. The machine can be repaired in 10 or 20 years using standard components. It is possible to make an outstanding machine using standard components. It is just the way you use them.
(Serge) This is a very simple, elegant design that was extremely difficult to execute. As an example, I had a conversation with a potential distributor who told me that he also built an amplifier without global feedback but it physically exploded in a few days. My answer was, "Now you understand why it took 16 years to make this work correctly."
Q: Moving to the preamp, when did you begin the design?
A: (Serge) Four years ago. Hervé has thousands of design ideas in his head. One of my jobs as partner is to keep focus. Originally, Hervé probably conceived of the design at the same time as the amplifier.
Q: Describe the journey to get to the release of the new preamp.
A: I originally wanted to share my design with the most people before it became a commercial product. I wanted to share the circuit with the DIY community, share it with other enthusiasts because I knew that the machine would be very expensive to make. There is a lot inside. The preamp is even more expensive because there are more than 1,000 components in the design – six hundred components for the motherboard and four hundred components for the phono preamp. Again, it is difficult to make this simple design work well. You need the correct power supply, the expensive 'mystery light' components for switching and volume, the DC offset has to be controlled and many other things. Although the signal path is simple, there are a lot of components to make it work properly.
Q: As to the design, why the unique gold and red case color?
A: It was a big controversy. All other brands are either gray or black. People said, "I can't put your amp in my system; it does not match." Now with the preamp, we have two matching components. Maybe when we launch a source component, like a CD player or integrated amp, the entire system will match. I wanted something different and fun. The 'eyes' and 'power nose' are on the amp. The preamp has a 'pleasure control' for volume and 'enjoyment source' for input selection. I believe that sometimes the audiophile life is taken too seriously. People listen for bass, midrange, highs, soundstage etc. but I just listen for music. I wanted to make my machines more fun, pleasing and human.
Q: You must listen for some specific sound qualities.
A: It is all about the music. It doesn't matter if the recording is good or bad; I don't care. If you have a good recording, it is better, but I prefer to listen to the music.
(Serge's answer to continue) Emotion! At the London Show, we spent a half day setting up the room. Our first listening session had no emotion. Maybe it was our exhaustion or not being used to the new room. However, the next day, goose bumps. We had three demo records to play. Every time we played the same tracks, I had the same emotional experience - even three days later. People would come back again and again. You watch them sit and unconsciously move to the music. They are touched by the emotion.
Q: I am fascinated by the mysterious volume control light system.
A: Mark Levinson, for example, uses a chip with trim resistors in a ladder configuration and they switch them with FET transistors. The problem with FETs is that you have a silicon junction and the signal is altered by the switch. You can use relays but the contact remains the problem. There is an electrical potential difference between two contacts so here we use a similar resistor ladder but we switch using our light system instead of relays. The entire process is digitally controlled with sophisticated software. The processor is always idle except when you touch a button so there is no active clock in the machine to disturb the sound.
Q: Keeping with simplicity, you did need a remote?
A: Yes, but only volume and mute since there are no digital readouts on the preamp. When the remote is activated, the LEDs change from red to green to show that the preamp is receiving the remote signal.
Q: No input changing by remote?
A:: No, generally when you change the source you have to get up and change the CD or record. Keeping with the original design, I did not want a remote but it was conveyed to me that this was necessary by our US importer.
Q: Let's take a quick tour of the preamp.
A: The entire component is dual mono beginning to end. The first board is the phono preamp, with over 200 SMD (Surface Mounted Devices) per channel but again, there are only eight junctions in the signal path from input to output. The balanced input card is a bit different because we put a transformer on the card. All inputs are selected between RCA or our BNC 50-ohm proprietary links. There are three BNC outputs for amplification (to allow tri-amping) and each output has its own dedicated buffer. There are no jumpers. We use tiny pads which are soldered or not soldered to make the switch for phono impedance and gain.
Q: Can the phono preamp settings be changed by the end user?
A: We can do it at the factory but if the end user can use a soldering iron, he can change it himself.
Q: What about phono gain?
A: The maximum phono gain is 66dB plus an additional 13dB in the line, so you have a lot of gain available.
Q: Resistive phono loading?
A: We have four resistors that combine for many loads from 100 ohms to 47k. There is no capacitive loading because the new MM cartridges do not require it. We do have an optional capacitor to kill RF interference.
Q: Again, is the resistive loading user changeable?
A: The end user can do it but it is better that we set it up. The standard configuration for MC is 60dB of gain and a 330 ohm load - a good standard.
Q: Speaking of cartridges, what is in your personal system?
A: We have a special EMT cartridge modified by Van den Hul. It is like a Colibri, just amazing but less hard on the sibilants and very sweet. He made 23 modifications, changing the diamond, cantilever wire, capacitors and more. It sounds fantastic.
Q: Let's discuss the batteries. A few designers have tried them with success but it is certainly not in the mainstream. The trend in high end preamp seems to be separate components with massive power supplies, high filtration and regulation with tons of current capabilities. Why battery power?
A: The problem with external power supplies is that you still have the umbilical connecting wire so the impedance in the preamp is higher. You need to add regulation inside it to lower the impedance of the power supply. No matter how much you filter the power supply, you still have residual noise. With batteries, you don't have any noise because there is no magnetic field.
Q: I am not an engineer but I have heard that batteries while low in noise, suffer from their own impedance problems.
A: That is true when you use a battery to power the circuit directly. Manufacturers sometimes think, "Okay, we use batteries so we don't need to regulate because there is no hum or alternating current." But it doesn't work like this. We have a twelve volt battery regulated at ten volts. The regulators lower the voltage because when a battery is full it outputs thirteen volts and declines as it discharges to about eleven volts. This is not good for the circuit if the voltage is not constant. Also the impedance of the battery is lowered so everything is happy.
Q: Describe the operation under battery power.
A: Like the amp, once it is broken in, you do not have to leave the preamp on or warm it up for best sound. It needs only fifteen minutes of warm up. Therefore, we recommend that you turn the preamp off when not used. When it is off, it is always charging the batteries.
Q: What is the playing time with batteries?
A: The playing time with batteries is 15 hours. After fifteen hours, the preamp will automatically switch from battery to AC and simultaneously charge the batteries. There is a small but noticeable difference in sound while it is charging. This is another reason not to leave the preamp on all of the time. When you are ready to listen, the batteries could be in a charging cycle.
Q: What about battery life?
A: The batteries, of course, are the highest quality Japanese Yuasa or American Genesis batteries. If you leave the machine on continuously, battery life would be about three years due to the constant cycling. If you turn the machine off after listening, the batteries will not be completely drained so the charge can start with maybe one half power reserve and you can expect perhaps four to six years of use.
Q: Does the preamp have to go back to Switzerland for battery replacement?
A: No, local service repairs in each country can change the batteries.
Q: What type of battery is used?
A: Twelve volt, five-amp lead acid because these are the only batteries which do not have a memory effect. They can be charged at any time at any level of discharge.
Q: What is your recommendation for after-market power cords?
A:: I tried some but I am not a tweaky guy. Tweaks will change the sound but I am not sure that they will improve the sound - different maybe but not necessarily better. If the incoming power is good, the cabling will have a lesser effect. You can get better results from just cleaning your contacts.
Q: Tell me about the Zeel links. Why create a non-standard connection?
A: Our system is single-ended. I really don't believe in balanced. With balanced, you either have to use transformers or twice the electronics. The preamp has balanced inputs and outputs with transformers. I prefer them because they are immune to hum. They are there to be compatible with the professional standard but for me, single-ended is much simpler. In addition to the single-ended and balanced sockets, we have the fifty-ohm input and output.
Q: If you were happy with single-ended connections, why invent another type?
A: There are too many differences among audio interconnects. These differences are not marginal. I examined the problem and wondered if it is really the cable itself or only a problem of mismatch. I conducted an experiment at the Geneva Engineering School and it showed that if you are not matched, you will have some signal reflections. Although these 'echoes' occur above the audible threshold, I found that when you are matched, the sound is much cleaner because you do not have these reflections. It is like the integrity of phase or speed. You do not have any timing errors.
Q: What is the maximum length of these Zeel links?
A: One kilometer! Yes, one thousand meters of cable! There is no loss of highs or transients because the signal is matched. When you have a reflection in the cable, the signal bounces back and forth. Square waves become rounder not because of capacitance or inductance but because the interaction of the reflected signal causes the square wave to round over the edge because each return step is added together not in phase. The sum of these reflected steps is a rounding edge of the square wave. When you are matched, there are no reflections and it works.
Q: Can you hear the difference on a short run of, let's say, seven meters?
A: I can tell the difference with a one meter run. I compared my old Kimber Reference Cable, which I loved, and while less than longer runs, it is still clearly audible - less glare.
Q: Do you supply the 50-ohm cable?
A: While any fifty-ohm cable will work, we use specially made Swiss cable - small, thin, very good isolation, silver-coated, and they sound slightly better than standard cables. Since they are very thin, they can be run under carpet or near the walls.
Q:: What does the future hold for darTZeel?
A: In the very high end, we will make a monoblock amplifier and possibly a source component like a CD player, but coming back to our 'sharing the pleasure' philosophy, we will then make an entry-level product such as an integrated amplifier. This is a real challenge - where to cut costs while keeping the darTZeel sound. Our goal will be to make a product available to 95% of the community. Sometime in the future, we might make a 'cost is no object' piece, maybe only ten pieces just for the fun of it. The success of darTZeel up to this point has been accomplished without any advertising. We go to shows and let people hear the amp. The best advertisement is to let people listen to the products.
.Hervé Delétraz Interview with Mike Malinowksi


Stereophile 2010 Amplification Component of the Year runner up.