YPSILON Aelius II 200w class-A hybrid monoblock amps

YP 15 AM AELIUS
NZ$ 66,995.00 pr (incl. GST)
Ypsilon

YPSILON - "We strive to reproduce music in a way that is true to the original recording."

New

Aelius II is a push-pull hybrid monoblock power amplifier using only two gain stages with no overall feedback providing power to drive real world speakers with unmatched transparency and musical involvement.  

The first gain stage is implemented with a valve, operated in single-ended class A , transformer coupled to the output stage. By using a transformer we avoid using an additional gain stage, so transparency and purity of the signal is preserved.

For this purpose a wide bandwidth (10-75 KHz) transformer is made, developed under extensive listening tests and measurements. The bandwidth of the transformer defines also that of the amplifier.

In Aelius II a recently developed input transformer is added that extends the purity of the signal path even further. It also gives the opportunity of a balanced input in the amplifier, adding versatility of using longer interconnect cables.

The output stage uses components of the same polarity (N-channel), working in the same topology.  The output of the amplifier is symmetrical so both output connectors, plus, minus, carry signal in opposite phase.

Great attention was paid also in the power supply design. It uses high current inductors for smooth and quiet filtering.

Aelius II is most certainly a revolutionary product having a unique set of features, refinement and transparency with power and control over the speaker.

Specifications

Reviews

Videos

Specifications

OUTPUT POWER BEFORE CLIPPING:  200W rms @ 8 ohm / 350W rms  @4 ohm
BANDWIDTH:  11Hz -75Khz  -3db
OUTPUT IMPEDANCE:  0,25 ohm
INPUT IMPEDANCE:  47 Kohm
GAIN:  X30 (29,5db)
INPUTS:  Balanced
POWER CONSUMPTION:  250W @ idle
DIMENSIONS:  425x425x230 (W xD xH)mm
WEIGHT:  45kg

Reviews

(Note: MkI review since replaced by newer MkII version) - The Aelius is yet another spectacular sonic and technological achievement from Ypsilon Electronics. I remain impressed by everything they do.
Michael Fremer - Mar 29, 2013 

REVIEW SUMMARY: "..... as a graceful, gentle, infinitesimal rounding of transients and sculpting of images that produced mesmerising three-dimensionality with zero negative consequences. It just sounded right. Instrumental attacks became alarmingly urgent and precise, but never clinical or etched. Sustain was generous and decays were effervescent, fading into pitch-dark backdrops. The Aelius was very quiet and super-transparent, and its micro-dynamic performance was as good as I've heard".

"The amplifier's proficient microdynamic expression, combined with its taut rhythm'n'pacing abilities, proved ideal..... and when he goes for the very top, where the "pingy" notes are, the Ypsilons fully fleshed them out. The sound of the hammer striking the strings, the excitation of the instrument's metal frame and the high-frequency wooden resonance of the soundboard were accurately reproduced in terms of time, space, tonality, and texture—not too hard, not too soft. If you've ever plinked those upper keys yourself, you'd recognise how right they sounded as reproduced by these amps—not that the rest of the piano sounded any less convincing."

"The overall sonic perspective produced by the Aelius was more forward than that of the D'Agostino Momentum or the darTZeel NHB-458 or the Musical Fidelity Titan—not in-my-face, but definitely more upfront. Yet compared to the darTZeels', the Ypsilons' images were somewhat more gracefully rounded, more three-dimensional, and texturally more supple.Vocal and instrumental timbres also were spot on, thanks to the Aelius's robust, full-bodied midrange. Overall, the amp's presentation of this sonic spectacular was tonally, spatially, dynamically, and rhythmically mesmerising, and its transient purity and transparency only added to my pleasure".

ETENDED REVIEW: I knew nothing of Ypsilon when I first saw its products in a room at an overseas audio show. Even though the speakers in this system were complete unknowns, I was convinced that it was the electronics that were responsible for the magical balance of what I was hearing. That was confirmed when I reviewed the VPS-100 phono preamplifier in August 2009 and PST-100 Mk.II preamplifier in July 2011.

Greek austerity ends at the factory door of Ypsilon Electronics. The luxury components designed and manufactured within are innovative, high-performance, visually elegant, and expensive. They're aimed at audio enthusiasts, mostly outside Greece, who can afford to indulge themselves. Obviously, no Greek would object—the nation's economy, and those employed by Ypsilon, can only benefit from this small company's success, however minor the contribution.

Ypsilon's Aelius monoblocks cost NZ$66,995/pair (incl GST). That's a lot of money, but compared to some really expensive gear, including the Wilson Alexandria XLF speakers ($200,000/pair) and Ypsilon's own SET 100 Ultimate amplifiers (US$125,000/pair excl tax), the Aelius may be, for some, as Ypsilon's slogan suggests, "untouchable . . . but not unreachable."

Tube-rectified tube input, MOSFET output

The Aelius is moderately large and blocky; it measures 16.6" square by 9" tall and weighs 99 lbs. It's specified as outputting 200W into 8 ohms, 380W into 4 ohms, or 500W into 2 ohms, with the first 60W in pure class-A. Its tastefully understated satiny finish, sculpted front accent, and blue LED slit match the looks of the rest of the Ypsilon line.

Electrical engineer Demetris Backlavas has designed a circuit for the Aelius that has only two gain stages and almost no passive components in the signal path. The single-ended class-A tubed input stage uses a single C3g pentode tube (rectification for this stage is supplied by another tube) transformer-coupled to the push-pull output stage of six matched pairs of N-channel polarity MOSFETs. There are no source resistors in the circuit.

An interstage transformer is unusual in a solid-state or hybrid amplifier; one is used here as a "perfect" phase splitter for the Aelius's push-pull operation, and as a step-down transformer to greatly lower the input tube's impedance to drive the capacitance of the output MOSFETs. Though the phase is split and the amp is push-pull, it's really two single-ended amplifiers with six transistors driving the plus terminal and six driving the minus terminal—a very unusual circuit.

I visited Ypsilon while in Athens a few years ago. One afternoon, using an amplifier he was designing, Backlavas demonstrated the significant sonic differences produced by swapping out various capacitors, transformer core materials, and other components. The guy is steeped in theory but, ultimately, guided by his ears. Like a great chef, he knows how to obtain and mix the best ingredients to produce a sublime dish.

Backlavas points out that, without the transformer, an additional one or two active stages would have been needed to split the phase and lower the impedance and that those additional stages would reduce the amp's notable transparency and signal purity. Of course, transformers have their own problems, and building one with a sufficiently wide bandwidth (in this case, 10Hz–70kHz) is both difficult and necessary: the transformer's bandwidth defines the amplifier's bandwidth.

Backlavas says that while the Aelius's circuit is in some ways similar to the Circlotron configuration used in some output-transformerless (OTL) tube amps, it is not a true Circlotron. Unlike the Circlotron's unity-gain output, the Aelius's output is greater than unity gain. The result, Backlavas claims, is an amplifier with the sonic purity of a single-ended design, with push-pull power sufficient to drive virtually any loudspeaker.

Easy Connections

The Aelius's flat rear panel made all connections easy. Each of the "pure copper and gold-plated" speaker terminals has a large, round, screw-in knob of frosted plastic. These knobs are big enough to produce enough torque for a secure fit with even the stiffest cable when tightened by hand, and there's enough space between them to accept spades of any size, as well as banana plugs. Don't diminish the importance of this aspect of amplifier design—there's nothing more annoying than stupidly designed and/or placed terminals that seem to have been created by people who have never actually connected a speaker cable to an amplifier. Pay attention to this when you shop.

There are both single-ended RCA and balanced XLR inputs, chosen with an adjacent switch. Also on the rear panel is a handy ground lift switch for thwarting ground loops; this disconnects the ground circuit from the chassis ground. As with all Ypsilon products I've reviewed, the On/Off switch is on the rear.

As Supplied

Ypsilon specifies for the Aelius new old stock (NOS) of the military-grade Siemens C3g tube, which has eight pins, a metal sleeve, and a minimum lifespan of 10,000 hours. Unbeknownst to me, my review samples had been fitted with a Russian-made Electro-Harmonix 6C45PiEH tube, each with nine gold pins, that had been soldered into circular eight-pin adapter plates. (More below about why the swap was made.) I didn't discover this until after a month or so of listening, during which time I was also reviewing the Dan D'Agostino Momentum monoblocks, and using as references darTZeel's big NHB-458 monoblocks.

With the 6C45PiEH tube, the Aelius produced a warm, voluptuous, somewhat darkly "tubey" sound that gave little hint of its solid-state MOSFET output (though MOSFETs are reputed to have a warmer, softer sound than bipolar devices). Yet despite the voluminous soundstage and generous bloom, instrumental attacks were precise and transients were cleanly delineated through much of the audio band, though the bass was less than taut, and not as nimble and as well controlled as I like it—and as I know the Wilson Alexandria XLFs are capable of producing.

Driving the very sensitive XLFs, the Aelius was probably running in class-A all the time, even when producing high (sometimes ridiculously high) SPLs in my moderately sized room. Considering the Aelius's class-A operation, zero feedback, and two-stage simplicity, it produced less transparency, and less of a direct, "straight-through" sound, than I'd expected. Nor, despite the use of tubes, did it produce the uncanny tonal neutrality I've come to expect from Ypsilon electronics.

My family visits during the holidays, and both of my sisters and my brother-in-law usually indulge me by spending 10 minutes or so listening to "what's going on down there" in my basement listening room. This time, the three of them sat there for well over an hour, and had to be prodded into going back upstairs. They sat through a side of Mel Tormé and Friends: Recorded Live at Marty's, New York City (2 LPs, Finesse W2X37484), and all of side 2 of the Beatles' Abbey Road. Unprecedented! What kept them sitting? The speakers, of course, but as driven by the Aeliuses, the width and depth of the Wilsons' soundstage was unusually enormous and enveloping—overwhelming, actually, and almost in our laps. Add a mesmerising ease of sound that produced both reasonably good resolution of detail and billowy amounts of air and spaciousness, and it made for a very "wow" experience for all of us. The Mel Tormé record, in particular, was as "you are there" live as I've ever heard it.

Still, to my more experienced and critical ear the sound was overripe, somewhat diffuse, and tended toward softness, both at the very bottom and in the lower midrange, despite the latter's most attractive harmonic richness and the overall sound's uncanny textural verisimilitude.

The Aeliuses reproduced full-bodied, woody-sounding pianos from good recordings of solo pianos, but the attack cheated on the soft, diffuse, romantic side—too soft to correctly reproduce the attack of either startling and appropriately hard fortissimos or delicate yet well-focused pianissimos, not to mention all the dynamic gradations in between. Of course, the sound was always pleasing, but in the way that some audiophiles tend to romanticise how live music actually sounds.

It took me decades to acquire a system capable of cleanly and accurately delineating the honky-tonk piano of Nicky Hopkins (not Ian Stewart) in "Rocks Off," from the Rolling Stones' raucous Exile on Main Street (LP)—not to mention a system capable of separating out most of the parts from what most critics (with crappy systems) declared, in the early '70s, was "total sonic murk"—not that the proper playback of that particular album was my long-term goal!

Clearly hearing instruments and voices heretofore buried in the mix has always been among the more revelatory experiences of a worthwhile system upgrade, though it's not as wondrous as when a new component increases the listener's understanding of the music. The softness of that piano part clearly demonstrated the general softness of the Ypsilons' sound, particularly in the lower mids.

Switching to the admittedly more expensive D'Agostino Momentums (US$55,000/pair excl tax), or to the hideously more expensive darTZeel NHB-458s (US$150,000/pair eco tax), revealed—at least in my system—not only the Aelius's transient softness, but a dab of Vaseline on its sonic lens. This made everything sound "good," but robbed the greatness from recordings that truly were. Transparency, in particular, suffered.

Normally, I would have simply reviewed the amps as delivered, but given that these samples strayed from the preternaturally neutral, natural sound produced by every other Ypsilon product I've reviewed or heard at audio shows, I thought it best to contact the designer. Plus, last year, when a pair of preproduction Aeliuses were on the East Coast for some reason, Backlavas had asked if I'd like to hear them. I'd said I did, but that I wouldn't comment on what I heard or didn't hear.

The review samples did not sound at all like the preproduction pair. As I recall, Backlavas did tell me that for his first production run he was changing the material of the Aelius's transformer core, among other things, which would affect the sound, but the differences in sound between the two pairs of amps were so big that I called him.

After inquiring about the overall softness, and asking if that was what I was supposed to be hearing, I was told to expect another pair of input tubes. When the box arrived, I wasn't surprised to find in it a pair of C3g tubes, as specified in the instruction manual. But when I removed the amplifiers' ornately machined top plates, I was surprised to find, inside each, a 6C45PiEH instead of a C3g.

At the 2013 Consumer Electronics Show, I asked Backlavas what was going on. It turned out to be a combination of designer second-guessing and bureaucratic bullshit. Since 2006, the European Union's RoHS regulations (which mandate that solder be lead free but not CRTs—a much greater source of lead contamination, you can be sure) require documentation proving that no part of a new electronic component contains hazardous metals. This essentially outlawed the use of NOS vacuum tubes, of which the C3g is but one of many models, because no documentation exists that can prove their compliance with the regulations. While many high-performance audio manufacturers use NOS tubes anyway and ship to EU countries, Ypsilon was concerned about this and sought an alternative, currently manufactured tube. The 6C45PiEH proved a good choice that produced "interesting" results, Backlavas told me, adding that the tube "has midrange energy and body but it's darker and warmer."

Currently, Ypsilon ships to EU countries Aeliuses equipped with 6C45s. More significant, the amps are manufactured with the 6C45 tube-socket base, making them incompatible with the C3g (which Ypsilon also uses in their VPS-100 phono and PST-100 line preamplifiers). Amps shipped to the US are fitted with the C3g base and are normally shipped with that tube, which Backlavas admits has "greater openness and transparency." However, he thinks which tube sounds best will depend on the system the Aelius is used in. He assumed that I'd be reviewing his amps with the less lush-sounding Wilson MAXX 3s, and so shipped the review samples equipped with 6C45s. So glad I asked!

When I'd replaced the input tubes with the C3gs and spent some time listening, I understood Backlavas's tube rolling—though I think it was an unnecessary defensive posture, even had I been listening through the MAXX 3s.

Clean and Direct

With the C3g tubes in place, and after about an hour's warm-up (both before and after the tube swap, I left the amps on continually), I sat down and listened. At first, they sounded like completely different amplifiers; later, the Aeliuses revealed themselves to be the same amps, but their soft and fluffy gatekeeper had gotten out of the way. The C3g tightened the screws on the musical framework, producing a punchier, more direct, more insistent sound. Little remained of those soft billows.

The Aelius's solid-state-ness now asserted itself more intensely, particularly on the bottom, where excess bloom gave way to grip and punch. The amps came rhythmically alive and physically assertive in a most pleasing and immediate way, yet in no way was the sound clinical or harmonically bleached.

I didn't hear the effect of the C3g as an identifiable "tubeyness" but rather as a graceful, gentle, infinitesimal rounding of transients and sculpting of images that produced mesmerising three-dimensionality with zero negative consequences. It just sounded right. Instrumental attacks became alarmingly urgent and precise, but never clinical or etched. Sustain was still generous—though not like before, when it was too much—and decays were effervescent, fading into pitch-dark backdrops. The Aelius was very quiet and super-transparent, and its microdynamic performance was as good as I've heard.

Like the Ypsilon VPS-100 phono preamp, which sounds like neither solid-state nor tubes, the Aeliuses, fitted with the same tube, sounded likewise: neither warm and fuzzy nor cool and clinical, but with a distinctly direct and upfront sound that perhaps had influenced the designer's decision to fit the amps with the 6C45 tube.

If Dan D'Agostino's Momentum amps were liquid and demanded an almost feminine listening melt, the Aelius amps produced the opposite sensation: a bracing masculine steeling and grip, a rush of adrenaline vs the Momentums' flood of endorphins.

A test pressing of Analogue Productions' upcoming vinyl reissue of Ray Brown's Soular Energy (it was reissued in 2002 on two LPs by Pure Audiophile, and before that in a Super Analogue edition from King Records Japan) produced exceptional clarity, hair-raising speed and transparency, and a profusion of accurate tonal colors from Ray Brown's double bass, Gene Harris's piano, and Gerryck King's drums, the cymbals being particularly spotlit (in a good way). The amplifier's proficient microdynamic expression, combined with its taut rhythm'n'pacing abilities, proved ideal for this trio recording. Harris is all over the keyboard in "Cry Me a River," and when he goes for the very top, where the "pingy" notes are, the Ypsilons fully fleshed them out. The sound of the hammer striking the strings, the excitation of the instrument's metal frame and the high-frequency wooden resonance of the soundboard were accurately reproduced in terms of time, space, tonality, and texture—not too hard, not too soft. If you've ever plinked those upper keys yourself, you'd recognise how right they sounded as reproduced by these amps—not that the rest of the piano sounded any less convincing.

Guitarist Grant Green's version of "My Favourite Things," from his The Complete Quartets with Sonny Clark, recorded by Rudy Van Gelder (2 CDs, Blue Note CDP 8 57194 2), produced a different sonic picture. There was definitely greater emphasis of the transient pluck and less on the three-dimensional aura around each pluck. As I wrote in the Momentum review, "A faster, more clinical-sounding amp might emphasise the transient at the expense of the aura; a slower, softer-sounding one might get the aura but fail to cleanly delineate it. Given that choice, I'd go for clinical over mush. . . ."

The Aelius with C3g tube definitely sounded more clinical than the Momentum (which produced more relaxed transients). I suspect that with the other input tube the Aelius would have properly reproduced the aura around Green's guitar, but would have failed to delineate it cleanly in space, and would have softened the transient. That's why I thought the C3g tube produced better sound with my system. I prefer correct, clean attacks, and that's something at which the c3G-equipped Aelius excelled, without sounding clinical or hard—unless the recording itself did.

Closer to the Action

The overall sonic perspective produced by the Aelius was more forward than that of the D'Agostino Momentum or the darTZeel NHB-458 or the Musical Fidelity Titan—not in-my-face, but definitely more upfront. Yet compared to the darTZeels', the Ypsilons' images were somewhat more gracefully rounded, more three-dimensional, and texturally more supple.

I'm always happy to play Lorin Maazel and the Cleveland Orchestra's recording of Gershwin's Porgy and Bess (LP, UK Decca SET 609-11), to hear how a system handles space. This recording, engineered by Kenneth Wilkinson, produces an enormous, well-delineated space and an exquisitely well-focused orchestral picture. The solo vocalists are also well back in space on the stage, as you'd hear in concert, and superbly focused and solidly three-dimensional, surrounded by a cushion of natural reverberation. If you're trying to stop someone in his or her tracks with music, it's a can't-miss record.

After a short opening fanfare (which, years later, Charles Strouse stole for the opening of Bye Bye Birdie) that highlights the brass and percussion, there's a long solo for upright piano, the piano in the distance, on the right. The Aelius excelled at reproducing the lesser-quality piano's somewhat tinny tonality, but pushed the instrument farther forward than usual. This was more than made up for by the well-focused image of the piano and the transient clarity of individual notes. When the chorus unexpectedly enters at center stage, their "Dah-doo-dahs" hovering in space, they, too, appeared farther forward than usual. (In this opening sequence of Gershwin's opera, which includes "Summertime," you can also hear where Peter Knight got his ideas for the orchestral arrangements he wrote for the Moody Blues' Days of Future Past, and even elements of Bernstein's West Side Story.)

Vocal and instrumental timbres also were spot on, thanks to the Aelius's robust, full-bodied midrange. Overall, the amp's presentation of this sonic spectacular was tonally, spatially, dynamically, and rhythmically mesmerising, and its transient purity and transparency only added to my pleasure. However, if the other components in your system exhibit even a hint of hardness, the Aelius with C3g tubes will accentuate it.

Norah Jones's The Vinyl Collection (7 LPs, Blue Note/Analogue Productions AAPP NJBOX 33) demonstrated the Ypsilon's superb midrange palpability. These records, remastered by Kevin Gray and pressed at QRP, are so quiet, their sound so velvety, that it seems as if you're listening on the other side of the mike, hearing Jones's voice before it's captured.

The Aeliuses put Jones's voice dramatically up front, tightly focused in three dimensions and as texturally full-bodied as it needs to be to sound real. Getting that means that there can be no audible leading edges to transients, no lower-midrange emphasis that might add a chesty quality, no sustain anything less than generous, no decay into black anything less than ideal. Jones whistles in "Little Room," and through the Ypsilons I'd swear she was whistling in my room. Not an easy illusion to create.

Switching to the darTZeels produced different sonic pleasures. The perspective was a bit less forward, the overall picture somewhat more relaxed. Images were somewhat less intensely focused, yet the articulation of transients was more precise, and there was a greater sense of the space around Jones's voice—as well as around Grant Green's guitar in The Complete Quartets with Sonny Clark.

Unique Circuit, Unique Sound

The Ypsilon Aelius, the D'Agostino Momentum, the darTZeel NHB-458, the Musical Fidelity Titan—all accomplished amplifiers, each with a different sound. Which is "correct"?

In the world of recorded sound and complex combinations of gear, there's no such thing as the "correct" sound. Certainly, some amplifiers are wrong, producing gross tonal colorations, transient artifacts, glaze, grain, glare, smear, etc. But at the level of the models I've just listed, none of those should be present, and none are.

The problem with absolutism in reproduced sound is that if you judge a component using your 20 favorite recordings, you're judging it against those recordings' tonal balances, and you end up in a maddening sonic feedback loop. That's why, in addition to my favourites, I include in my listening dozens of unfamiliar recordings, plus some that I know sound bad.

At an audio show a few years back, I'd just finished listening, through Krell amps and speakers, to a wide variety of sonically reliable LP tracks that I'd previously recorded to CD and that I'd already heard through dozens, if not hundreds, of good systems. They sounded superb. A guy walked in and asked to hear his favorite recording, an opera. Within a few bars, it was obvious that this recording was awful: bright, glazed, hard, and spatially compressed. This was not the inherent sound of those components in that room. Yet this was the single recording with which he gauged a system's performance. He stopped the disc, declared the sound in the room "awful," left, then spent the rest of the show telling everyone how bad the sound in Krell's room was. But what was clearly awful was his CD.

The Ypsilon Aelius's sonic character, like that of the D'Agostino Momentum, was obvious early on, but so fully realised from top to bottom as to be unnoticeable after a short period of acclimatisation. That left only the enjoyment produced by an amplifier that is unique in both design and sound. The Aelius's top-to-bottom rhythmic agility may be in a class of its own. Its bottom end was nimble, clean, and well extended, and did the best job of controlling the woofers of the Wilson Alexandria XLFs of any amplifier that's been here since those speakers arrived, though the darTZeel NHB-485 was close enough. The D'Agostino Momentum was somewhat softer, the Musical Fidelity Titan softer yet.

With the C3g tube, the Aelius's reproduction of the highs was as fast, clean, extended, and assertive as its reproduction of the rest of the audio band. It all added up to a rhythmically spectacular amplifier that was like a shot of adrenaline. That might not appeal to the Lincoln Town Car sound crowd, but definitely will to those who like to press the pedal to the metal, even when listening to chamber music. On second thought, maybe with the alternate input tube, the limo crowd might like it too. The great thing is, if you're in America, you have freedom of choice, and with it, Two! Two! Two amps in one!

Conclusions

Ater installing the stock C3g tubes, it took me a while to warm up to the Ypsilon Aelius monoblocks. But with the tubes originally supplied, the sound was too warm (though perhaps not for you). With the C3gs, the Aeliuses were definitely not too warm. Coming from the polar-opposite D'Agostino Momentums required a period of adjustment—but not because the Aeliuses were too bright, too fast, or too anything. Their sound was simply too different—but equally valid.

The Aelius amps were just right if you like a tight, fast, nimble top-to-bottom ride, if you like sounds so transparent it's almost alarming, convincingly yet not analytically precise transients, and three-dimensional imaging—all without paying the high price of too-sharply-defined edges or a clinical, soulless, harmonically bleached sound.

The Aelius is yet another spectacular sonic and technological achievement from Ypsilon Electronics. I remain impressed by everything they do.
…….Michael Fremer

(Note: Aelius MkI review - since replaced by MkII version) - I was very tempted to hold on to them and make them my new reference. That would have been a radical jump from my Soulution 710 Stereo Amp. Yes, they're that good
Marshall Nack - Sept/Oct 2014

REVIEW SUMMARY: "ever go shopping for a winter scarf? I like to test the "hand" of each offering, noting quality and price. The acrylic one would do the job, but it doesn't feel so nice. How about the wool or the cashmere blend? Silk, maybe? Any one of these materials would do the job and each has its own "hand". Don't we go through the same process with components? In this analogy, the Ypsilon Aelius Mono Amps are the equivalent of the finest silk-cashmere blend. They have the nap of lux on your ear; their sound feels good there".

"Whether the Aelius was paired with the matching PST 100 or my Trinity Preamp, the verdict was the same. These products are communication specialists. Everybody enjoyed them".

"I was very tempted to hold on to them and make them my new reference. That would have been a radical jump from my Soulution 710 Stereo Amp. Yes, they're that good,"

EXTENDED REVIEW: I'm in a smallish, wood paneled, recital hall. Perhaps it was someone's library, now re-purposed for concertizing? Mezzo-soprano Ann Sofie von Otter is telling us little stories in song. The sound is warm and inviting, the feel of the space is close.

Oh, snap out of it—I'm in my listening room, of course, and it's just another session at Nack Labs. I just installed the Ypsilon Aelius monoblocks; the matching PST 100 Mk. II Preamp is up stream and we are listening to Mots d'Amour (DG 471 331-2). The Ypsilon pair conjured this potent magic, transcending each individual component's contribution. The math in this case is something like one + one = three.

From whispers to near shouts, the system scaled realistically. Dynamic transitions were uncommonly convincing. I hasten to add this display is from an unlikely source—simply a mezzo-soprano with piano accompaniment on an average Red Book CD, nothing audiophile. For such small forces—why do you need such big, expensive boxes and so much horsepower (220 watts/8 ohms)?

If you've ever been proximate to a professional opera singer, you`ll know why. You won't have to get out the SPL meter to register her dynamic range.

And it really does show off the Aelius' range, which traveled right along with Ann Sofie. When her voice changes, you can rest assured it is generated by her efforts at vocal production, not mechanical strain or discontinuity generated by the amps. This occurs in a totally believable way.

On the flip side, the Aelius revealed in detail the many little devices she employs to communicate her interpretation. She is continuously expressive: there's not a wasted note or a dull moment. This is what makes her great.

I can't help contrasting this to Brazil, a CD I purchased recently featuring Stacey Kent as guest vocalist on a couple of tracks. Ms. Kent sings in a breathy whisper. There is no dynamic range in her flat, affectless, monotone; nor is there an attempt an interpretation. She is popularly esteemed and has found a niche among the audiophile crowd. My disappointment was deep—the attraction totally escapes me.

The Ypsilon Signature

Admittedly, what Ann Sofie is communicating are aspects of the performance best heard on gear of the caliber of the Aelius. It won't come through with most tube gear. Solid-state? Fuhgeddaboudit.

This is a subset of resolution, but not one many designers are attuned to. Indulge me for a moment, please. We all know a components voice is like a window into the designer's taste. Where one engineer may seek a clean, neutral, powerful sound, another may be after classic tube sound. The possibilities are expansive, but in all cases, the designer goes through an iterative process, refining circuits and parts until he hits upon the one that speaks to him.

The folks at Ypsilon have their ears tuned for the intimate, intensely human details of a performance, qualities that are often found in classic Japanese gear like Audio Note Japan. Both brands employ tubes, transformers and uncommon circuit design to bring out these "unspoken aspects of the performance."

They are a particular specialty of the Ypsilon sound. I'm not going to delve deeply into these soft virtues, as I'll just be repeating what I wrote recently in my PST-100 review. In brief, what these brands bring to the table is:

Wholly satisfying timbres
Proper dynamic relationships
Enhanced musical flow
Your mind goes "Ah" when it hears this. Timbres especially are complex with an accent on beauty. Perhaps they are a bit more lush and beautiful than heard live. 

Rounding out the Picture

The portrait of the Aelius I've drawn so far shows off its expertise in the soft virtues. Indeed, that is this machine's forte. (Actually, that is Ypsilon's forte.) But there's more. Time for another musical example.

I'm a fan of the Count. The trouble is he was so popular and prolific, in and out of the recording studios often, that pruning is necessary to sort the wheat from the chafe. I came across this Verve LP from 1964 by happenstance and it's a good one, easily beating the many Pablo LPs on people's lists. Plus it's available for a song.

What a band! This is the kind of playing that only gels after years on the road together. This isn't a pretty recording—I'm sure that's not what Basie wanted—and just by looking at the grooves you can tell Basie Land (Verve V6-8597) is cut hot. The brass tutti on this LP snap and sizzle. They are so hot, they can sound raw and unvarnished. However, there's a difference between these jagged brass rim effects and the distortion that an audio component produces when it can't handle signal peaks.

Those brass tutti sound like they're supposed to through the Aelius.

Macro dynamic volleys test the limits of my associated components. This was really surprising—those macros did not give up any heft compared to the Soulution 710 or the Audionet AMP monos. (Although they couldn't match the seismic shocks generated by the Tenor 175S Stereo, the CH Precision A1 in mono, or the Audionet MAX monos.)

Nor did it fall short in detail retrieval—the amount of information presented is right up there, as well. Ditto for the soundstage, which is highly dimensional and wall to wall, seamless across the width and layered in depth.

The Count and his men are full size and the brass instruments are hard left/right, located in the speakers. Alternating with the slam of the tutti are occasional soft, almost caressing, trumpet and sax solos, with Basie's piano straight down the middle sounding rather delicate. The Aelius can morph like that. It can vary style to suit whatever comes along and will not force the music into bombast.

Tonal Description

This is a great LP to demo macro prowess and to show off how well the Aelius maneuvers around sharp corners. Transients are fast moving, although with a soft edge, while decays lengthened moderately. The midrange presents a "see into" clarity that revealed tons of inner life; the bass is well represented, but could be tighter and have more texture; the treble is sweet and extended. Overall, the frequency sweep is smooth, with lots of body and flesh, and a tad warm.

A Well-behaved Soundstage

When I reviewed the PST 100, I was struck by its soundstage. It is remarkably well-behaved—it never does anything offensive. So it is with the Aelius.

There are no sharp image borders—there is no sharp anything. The stage has a soft quality and is a bit laid back. Images are diffuse with lots of air around them, defined more by timbre than by precise borders. It does not POP like some of the powerful solid-state amps I've had in lately. In this manner, the Aelius insures it will never sound harsh or abrasive.

The stage forms at the speakers, recedes from that point and does not budge. Regardless of the musical content, the front line does not advance forward from the plane of the speakers. This is how sound behaves in large spaces like rear parquet or first tier at Carnegie Hall, an ideal setting for classical music listening.

In general, those powerful solid-state amps move your perspective closer, more like mid-parquet at Carnegie. And they tend to jiggle the soundstage back and forth in tandem with the SPL or frequency. That is, it comes forward when it gets loud or has a lot of treble content.

Ancillary System: the PST 100 Mk II Preamp

Back when this review project was in the discussion phase, the importer decided to send both the Ypsilon amp and preamp and requested separate reviews. The PST 100 Preamp came first and I had time to get acquainted. It brought back fond memories of the VPS 100 phono stage I reviewed a while ago. These components make a lasting impression—they don't sound like the rest of the pack.

I had one apprehension going into this review: those two preamps had the same voicing, including some tubey colorations. Would the Aelius share that and, if so, would it compound, pushing over the edge into euphony?

That didn't happen, because the Aelius hews closer to center on the dial than the two preamps. The Ypsilon signature is more moderate. Panel mate Sheldon summed it up well: the Aelius is more of a reporter than a colorist/interpreter.

More Associated Equipment: CH Precision

For a while I had the CH Precision D1 SACD Player and C1 DAC/Pre as a two-box digital source fronting the Ypsilon PST 100 Preamp and Aelius monoblocks. WOW! This is the incredible teleportation machine I described at the top of this review. There is an awful lot of internet buzz about the CH front-end—many people think it's the ultimate. I could hear why. This system represents a benchmark in my audio odyssey.

That old stereo magic happened often now. The myth is it recreates the live event—but who knows? It is not the same as the teleportation created by SET gear, like Audio Note Japan. SET gear has even more intimacy and places you up close and personal with the musicians, like they are playing in your room, just for you. Magical, yes.

Cosmetics and Operation

Each Aelius is a large chunk of brushed aluminum weighing 100lbs. The chassis is fabricated in Germany and Italy. Everything else is made and assembled in-house in Greece.

The face plate is adorned with the Ypsilon logo engraved in the lower right corner, just like the preamp and phono. The logo appears again, laser cut into the top plate—a distinctive touch. Louvered heat sinks along the sides and top provide dissipation of the considerable warmth generated. The rear panel has the expected functional provisions and nothing more. The Aelius is understated, elegant and utilitarian; it looks different from most amps.

Installation is a snap. Place them on a good amp stand, allowing for air circulation, and plug them into the wall or a passive distributor strip. (At this performance level active conditioning should be avoided.) Set the XLR/RCA input switch on the back and push the old-fashioned On/Off rocker switch.

The blue power bar in front lights up and that's it. Wait 30 seconds for tube warm up and you're good to go. (There is no notification when it passes from warm up to Ready State.)

A couple of notes: The Mundorf binding posts are really nice—over-sized and very easy to use. I wish more manufacturers used them. The chassis, while of formidable thickness, rings when struck by a knuckle wrap. I didn't attempt to dampen it, but you may want to.

Design

The Aelius is a two gain stage, "bridged single-ended design" that possesses the musicality of pure single-ended and the power and control of push-pull. The input stage uses a Siemens C3g valve and is coupled to the MOSFET output stage with a C-core transformer of very wide bandwidth (-3db@ 10Hz-90kHz). The first 60 watts are Class A, then it moves into Class A/B for a rated output of 220-wpc into 8 Ohm.

The power supply uses an EZ81valve for rectification and a transformer of very large size and special winding techniques.

It is said the secret of the Ypsilon sound is their transformers. They are painstakingly hand-wound—a tedious, time-consuming task. Every product in the line has them: the Aelius has two transformers and three power supply chokes.

Conclusion

Ever go shopping for a winter scarf? I like to test the "hand" of each offering, noting quality and price. The acrylic one would do the job, but it doesn't feel so nice. How about the wool or the cashmere blend? Silk, maybe? Any one of these materials would do the job and each has its own "hand."

Don't we go through the same process with components? In this analogy, the Ypsilon Aelius Mono Amps are the equivalent of the finest silk-cashmere blend. They have the nap of lux on your ear; their sound feels good there.

This is my third taste of Ypsilon componentry and it has been consistent. Within that spectrum, I'd place the PST 100 Preamp and VPS 100 Phono Stage together on the musical side in their voicing; the Aelius mono amps tack closer to neutral.

Whether the Aelius was paired with the matching PST 100 or my Trinity Preamp, the verdict was the same. These products are communication specialists. Everybody enjoyed them.

I was very tempted to hold on to them and make them my new reference. That would have been a radical jump from my Soulution 710 Stereo Amp. Yes, they're that good. 
........ 
Marshall Nack

(Note: Aelius MkI review - since replaced by new MkII version) - With them, it is the sum total of everything they do -- all to a very high level -- that's distinguishing, and that so much of what they achieve is rare among amplifiers no matter the price.
Marc Mickelson - March 12, 2012

SUMMARY: 'The presentation was both truthful and beautiful…..a balance in portions so nearly ideal that any deviations are trifles in light of the totality of their performance. No amp will please everyone, the Aelius has a better chance of achieving this than any amp I've heard".

EXTENDED REVIEW: Ypsilon is the twentieth letter of the Greek alphabet and Aelius was a noted Greek scholar and orator, so it will come as no surprise that the Ypsilon Aelius mono amps come from the cradle of Western civilization. These 200-watt push-pull monoblocks are sophisticated hybrids, featuring a tube input stage using a single C3g -- a fairly obscure metal-sleeve tube -- and a MOSFET output stage. They output 60 watts of their power in class A, which means they'll run this way for the majority of listening, but perhaps even more significant is Ypsilon's claim that the amps offer single-ended sonic purity and push-pull power. While this sounds immediately like marketing hyperbole, Demetris Backlavas, the amp's university-trained design engineer, can back it up. He cites the Aelius's "balanced (or you may call it bridged) single-ended output stage," for which both phases, plus and minus, carry signal. "The difficulty of implementing this output stage," Backlavas went on, "is that it requires to be driven with a perfectly balanced signal. And this was done with an interstage transformer, which took a long time and many trials to bring it to the level of performance we wanted (-3dB@13Hz-70kHz)."

What this means in non-engineering speak is that the Aelius's circuit is sort of a double hybrid: tube and solid state, balanced and single ended -- with no feedback, an important design consideration for Backlavas. All of this makes for an amplifier that is unlike any other produced today -- at least among the ones I'm aware of. Ypsilon itself is just as unique. First, the company manufactures its own transformers. The cores are outsourced, but the design and winding happens at the Ypsilon factory. Second, the solid-silver hook-up wire used in each Ypsilon product is proprietary, drawn from bars of silver. A jeweller does this to Backlavas's specifications.

Connection to the Aelius is via RCA or XLR input, but counterintuitive perhaps to what I've divulged so far, only the former is recommended for achieving the highest performance from the amps. The balanced input for the review amps included a transformer not manufactured at Ypsilon, and this led to an obvious veiling -- with this "veiling" not being part of the Aelius's sound through the single-ended input. It honestly did sound like something additional was in the signal path, which was literally the case. Realising this, Backlavas will be removing the transformer in future production runs. For connection to the speakers, the amps use binding posts with frosted caps that look like they were made specially for the frosted-silver Aelius.

One feature of the Aelius that I applaud loudly is its ground-lift switch, which could save you the time and inconvenience of using cheater plugs if you have a ground-loop issue with your system. This is also an outward sign of one of Backlavas's preoccupations: eliminating noise. He seems to have hit his mark. After initially installing the amps in my system, connecting to the preamp and speakers, and turning everything on, I thought I had overlooked something, because there was absolutely no background noise -- not even the omnipresent tube rush I had gotten used to hearing. I put my ear up to the tweeter and heard complete silence. I hit play on the CD player, expecting nothing to happen, and music poured forth. Luckily I didn't do something dumb like crank up the volume when I thought things were amiss.

The amps definitely needed warm-up after turn on, sounding sterile when they were cold and then coming into character after 30 minutes. However, they seemed so stable, so imperturbable, that I left them on almost indefinitely, unless I knew I wouldn't be listening for days, the amps always being ready to make music.

The sound of the Aelius monoblocks embodied seeming opposites. On the one hand there was an overwhelming clarity, which mixed supreme retrieval of musical detail, transient definition, and front-and-centre tonal neutrality. On the other hand, there was an inherent robustness and density that tracked from the highest highs, through the mids and into the bass. Add in that nonexistent noise floor and you have, I'm confident, one of the most complete amps extant -- an amp whose personality was literally devoid of obvious weaknesses. This is not to say that the Aelius did everything better than all other amps -- that beast has yet to be created. However, within a broad level of performance, the Aelius competes with any amp I've heard -- and I suspect any amp made today.

Hearing familiar recordings was often an act of discovery, especially those whose sound is stellar in an absolute sense. They could sound both fresh in specific ways and true to life generally. One recent and lucky addition to my collection is the Mobile Fidelity version of Led Zeppelin II [Atlantic/Mobile Fidelity MFSL 1-065], the only one of Zeppelin's albums reissued by MoFi (thus far -- we can always cross our fingers for the future). It has become the album I play for non-audiophiles who want to either experience my system or hear the difference between digital and analog, and it never, ever leaves them in anything short of complete awe. I paid a mere $35 for my near-mint copy -- more than its original selling price, but $100 less than the going rate on eBay.

If you grew up in the 1970s or 1980s listening to FM rock radio, you know side two -- beginning with "Ramble On" and closing with "Bring It On Home" -- by heart. It was a new experience with the Aelius monoblocks. The guitars had more pummelling bite and the bass and drums were better defined and weightier. On side one, the ping-pong stereo effects of "Heartbreaker" whizzed between the speakers with dizzying suddenness. No matter its version, this LP will never be a test of dynamic range, as the music commences at loud and proceeds to louder still, but that's part of its relentless charm. As much as the Mobile Fidelity remastering, I'm convinced, the Aelius monoblocks made this blues-rock war-horse sound exhilarating.

An amp that can do that is a rare thing -- if and only if it doesn't skew the spectral balance by goosing a particular region or adding some amusical artefact that can enliven in the short term but wear thin over time. About the most that can be said about the Aelius monoblocks in this regard is that their perspective is more forward of mid-hall, giving them an insistence that imparts an agreeable vividness to the music. This is easier to appreciate at lower listening levels, where you won't have to aurally squint to discern micro-dynamic contrasts, than higher ones, but the amps' inherent grainlessness never made it an issue. When Miles Davis pulls out his mute, forwardness and especially treble grain have nowhere to hide. While Someday My Prince Will Come is not Miles at his vital best, it's still has some lovely playing, including John Coltrane's final work for the leader's first quintet. I have both the 45rpm LP [Columbia/Analogue Productions APJ 8456-45] and SACD [Columbia/Analogue Productions CAPJ 8456 SA] and, as with Led Zeppelin II, the music was rendered with such excitement with the Aeliuse that I began to reevaluate the playing. The digital version didn't have quite the same lateral spread and the treble was a little less liquid -- both of which the Aelius amps revealed.

Roy Gregory likes to talk about how great components actually make orchestras, ensembles and bands sound like they play better -- more true to the music and their own intentions. This idea popped into my head as I listened to Someday My Prince Will Come with the Ypsilon monos in the system -- the sound being infinitely well resolved for sure, but the playing also being tighter and (for lack of a better way to express it) more effervescent. This was also apparent with the 45rpm version of Seven Steps to Heaven [Columbia/Analogue Productions APJ 8851-45] -- the second incarnation of Miles' quintet and a much more formidable session. This is what great audio gear should do: make the work of great musicians sound greater still.

While the Aeliuse may have a tube in their signal path, there was nothing classically tubey about their sound -- no cloying midrange, no bass bloom at the expense of speed and slam. Perceived linearity ruled, the mids having a meatiness that, once again, is rare for an amp that's as tonally evenhanded as the Aelius. The bass was taut and muscular, more deep than bloomy and warm, and it possessed real power, especially with kick drum like that on Keith Richards' Main Offender [Virgin V2-86499]. The realism quotient of this recording is something to behold, the Ypsilon amps conveying not just the pop and sock of the drum kit but also the sharp barrage of the electric guitars. In fact, if you've heard this CD (it's also available on vinyl, but expect to pay dearly for it), you have a sense of the personality of the Aeliuse: a slightly forward perspective, vividness throughout the music's entire range, fleet transients that decay into blackness, roaring power.

And copious air throughout the soundstage. Darker-sounding amps can cramp things, conveying the presence of the musicians better than a well-rendered sense of the space in which they perform. While the Ypsilon amps leaned to the latter, they weren't devoid of warmth and dimensionality. At the recommendation of Richard Gerberg, the US ProAc distributor, I've been listening to a lot Sun Kil Moon, the moniker of Mark Kozelek, founder of the Red House Painters. His music and voice are reminiscent of Harvest-era Neil Young, and both bordered on luscious with the Aeliuses, which neither turned his singing into sugary mush nor emphasised the nasal quality that gives it character.

The presentation was both truthful and beautiful, and this is what the best components achieve -- a balance in portions so nearly ideal that any deviations are trifles in light of the totality of their performance. This is the Ypsilon Aelius in summary. While no amp will please everyone equally, the Aelius has a better chance of achieving this than any amp I've heard to date.

Hybrid hoe-down

While hybrid amps like the Ypsilon Aelius make a great deal of sense, because they hold the promise of combining tubes and solid state, there are surprisingly few of them. The dean of this select group is the Lamm M1.2 Reference (US$22,290), which, if you include its previous version, the M1.1 (and the Madison-Fielding M1 before that), has been on the market for almost twenty years. Obviously, the core design of this amp has great validity, both in terms of sonics and reliability: a tube input stage using a single 6922 followed by a MOSFET output stage running in class A. There's much common ground with the Aelius here, although Vladimir Lamm has never manufactured his own transformers or spec'd his own hookup wire.

I've used the M1.2s as my reference for over five years. For reviewing, they offer great flexibility, as they have both RCA and XLR inputs and there is no discernible sonic difference between them. You probably can guess that the Ypsilon and Lamm amps do not sound like the near relatives that they are. While it's possible to discern the tube and transistor sides of each amp's personality, the Lamm amps take on more of the traditional traits of tubes, displaying greater richness and warmth, a meatier and more expansive bottom end, and sweeter treble than the Ypsilon amps. The Aeliuses have less of an overt tonal signature, though the density of their mids might make you question this. They are faster into and out of each note, and their decay is more apparent, likely due to their lower actual and perceived noise floor.

Main Offender illustrated the differences of the two amps well, the Lamms imparting greater heft to the Richards' lead playing and that of the bassists, while the Ypsilons positively launched each drum strike into the room, portraying more skin than the Lamm amps and, once again, conveying greater decay amidst a wide, deep soundstage.

Yet, these differences don't invalidate the notion that both amps offer a wide-ranging set of strengths and a completeness of purpose. They prove once again the immutable law that similar design goals can lead to different sonic outcomes. Such is the diversity of human nature -- and the variety of sounds that can still be deemed hi-fi.

The promise of promise

Truly great amps, like their equals in other product categories, are complex sonic entities. Some distinguish themselves by pushing ahead the performance in one area, while others build on a defined set of traits, shoving them all to new heights. The Ypsilon Aeliuse fit into neither of these camps, and yet they are certainly "truly great amps." With them, it is the sum total of everything they do -- all to a very high level -- that's distinguishing, and that so much of what they achieve is rare among amplifiers no matter the price. I've heard amps that track the signal with as much speed as the Aeliuse and amps that are as quiet as the Aeliuse, but not amps that possess these qualities along with the same midrange dimension and the same bass power -- the same level of overall realism -- as the Aeliuse, all in one package.

The Greeks have been responsible for advancements in engineering, transportation, mathematics, sport, cartography, philosophy, literature -- the list goes on and on. Even more upscale in the Ypsilon lineup are the SET 100 Ultimate monoblocks, which are as large as computer servers and cost as much luxury cars -- each. Until I hear for myself that they fulfil their enormous promise, the Aelius monoblocks will more than ably represent the audio advancements of the Greeks -- and Ypsilon.

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Ypsilon Electronics, Ypsilon Amplifiers, Demetris Backlavas