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Zesto Audio Bia 120 Stereo Power Amplifier

When I first met George Counnas, President of Zesto Audio, the company had only one product, a splendid phonostage called the Andros (Issue 222). At the time, he told me a high-level preamplifier was on the way, but, when asked about a power amplifier, added he had neither interest nor plans for one. But when the Leto linestage turned out to be as splendid as the Andros, I figured it was only a matter of time before an amp came along. Counnas was refreshingly candid about his change of mind: “I needed it to round out the line.” For all their pretentions to mixing and matching components, quite a number of audiophiles seem to like their electronics from the same manufacturer, preferably consistent in visual style. So here is the Bia 120 to make the Zesto duo a trio. I’ll not indulge any suspense: Counnas is plainly a gifted designer who knows his way around circuits and sonics, and here hits the trifecta with this drop-dead gorgeous sounding amplifier.

Gorgeous looking, too. George’s wife Carolyn carries over her signature styling from the Andros and Leto, and the Bia 120 features the same split-level chassis found throughout the line.

With a graceful, wavelike pattern set in light silver aluminum bas-relief against black on the base, and the grand-piano-shaped (viewed from the top) upper chassis (housing the large toroidal transformer) with a curved polished-chrome fascia that reflects the softly glowing tubes, the amp makes a stunning impression. An elegant touch of visual rhythm is the repetition of the front-panel wave in the side vents on the upper chassis. As with its siblings, you’ll want to keep the Bia 120 out in the open for all to see, which is mandated anyhow by how much heat it generates, which is considerable because it’s 60Wpc in a push-pull output stage that completely eschews negative feedback and is operated in pure Class A.

Why Class A in a tube amp, which, after all, is not supposed to exhibit the typical solid-state notch when the signal crosses from positive to negative? “Unlike Class AB, where the A part is small and the B part happens only when the signal ‘turns on’ the tubes,” says Counnas, “in Class A, the current is going through the output tubes and not waiting for the signal, which gives you a more dynamic sound because the tube is constantly charged; it’s on all the time.” Doesn’t this shorten tube life? “Theoretically yes,” he answered, “but not by all that much in the Bia because the tubes aren’t being run that hard.” As for the absence of negative feedback, this is a prejudice from the early years of solid-state, when negative feedback got a bad rap because ridiculously large amounts were applied to transistor amplifiers to achieve distortion figures with four and five zeroes to the right of the decimal point. Trouble was, while this led to impressively low measured figures of steady-state distortion, it didn’t necessarily translate into good sound, especially when it was used in substandard circuits to overcome the severe limitations of the transistors themselves. Negative feedback is effective mostly when the basic circuit and parts are already of good or better quality, whereupon judiciously applied in small amounts it can improve performance. By the time Counnas finished designing the Bia’s circuit, he decided, based on measurements and listening evaluations, that he didn’t need any. “All it did was reduce dynamic range while adding nothing sonically.”

The Bia is a dual-mono design, with auto-bias and a large toroidal transformer. It features fully balanced and single-ended jacks and has heavy-duty binding posts with 4-, 8-, and 16-ohm taps. Owners of original Quads and very early LS3/5as (16 and 15 ohms, respectively) should take note: This is one of the lonely few modern tube amps that will match them optimally. Like all Zesto products, every Bia is broken in 50 hours before being boxed up, and is totally hand-made in the USA.

Counnas’ goal was identical to that for his phono and linestages: a component that approached the neutrality of solid-state with the attractive “tonality of tubes.” He succeeded spectacularly with the preamps and does so again here, though “approached” is the operative word, about which I’ll have more to say anon. Cut from the same sonic cloth as previous Zesto products, the Bia’s personality consists in a completely seductive musicality, free from the usual sorts of electronic colorations and artifacts, for a presentation that never, ever sounds electromechanical, instead drawing all attention to the music, which is reproduced in a wholly natural-sounding way. I simply never found myself thinking of reproduction as such or any of the typical audiophile categories—scintillating highs, slamming lows, liquid midrange, yak, yak, yak—rather about the music and music-making. Right now I’m listening to Valentina Lisitsa playing Liszt’s Totentanz and wallowing in the waves of sheer sonority, the way her generous use of pedal never seems to obscure the lines and textures, the control of the dynamics from delicate whisper to barnstorming roar, and bass that is exceptionally solid, extended, articulate, and powerful, with no need—thank you very much—to append the usual “for a tube amp” qualification. No wonder Counnas, who seems to love Greek names, christened this after Bia, daughter of Zeus and Styx, and the personification of force and raw energy.

Counnas told me that one of his goals was that if critical listeners didn’t know what they were listening to, they wouldn’t know whether it was solid-state or tubes. There’s certainly no hint of anything that some dyed-in-the-wool tube fanciers still don’t like about solid-state (even though almost no modern transistor amps suggest any of the nasties of the early ones). At the same time, however, they just might be a little disappointed that the Bia equally betrays so little of old-fashioned tube character either. There is something so completely natural about this reproduction that I really do find myself at a loss for words to evoke it. To be sure, it’s tactile, rounded, gloriously dimensional, and “continuous”; there’s nothing edgy, sharp, or overly articulate about it; it’s not “liquid” as such or excessively smoothed over (though it is extremely smooth); textures sound to me like the textures of real voices and instruments; there is zero impression of grain (I mean no evidence at all); transparency is not a concern; and detail is as detail should be, to be noticed but not zeroed in on. And it’s got by far lower perceived distortion than any tube amplifier past or present with which I’ve got more than casual acquaintance. In fact, the only tube amps in my experience that may trump this one for overall neutrality are McIntosh’s MC275, though take that “may” for all its worth, as it has been more than a few years since I reviewed those amps and my system was somewhat differently constituted then.

When it comes to dynamic range, the thing is wowie-zowie with a vengeance. I am gobsmacked by the prodigious levels Counnas gets out of these sixty watts, even Class A tube watts: I wish I could take all the audiophile cowboys who say Quad ESLs cannot play loud enough and force them to listen to the clear, clean, completely unstrained levels I’ve been enjoying daily with this combination. I played some piano recordings louder than they would be if the pianos were heard in real recitals, and certainly than I could listen to them comfortably, and neither the (very inefficient) 2805s nor the Bia evinced any strain that I could detect. The same is true for orchestral recordings, while voices have to be heard to believe (how refreshing not to hear sibilants unduly accentuated).


Imaging? Holographic. Moreover, there is something so preternaturally spacious about the reproduction it may constitute a subtle coloration, though if so, it’s a very attractive one. Put on really well recorded orchestral music, like any of John Eargle’s on Delos, for example, and the impression of size, scale, bloom, and vastness is spine-tingling indeed. The same is true for intimate music: I’ve been enjoying the Balcea’s traversal of the Beethoven quartets, which are very naturally recorded with a good recital hall’s row G-M perspective—close my eyes and the ensemble is simply there in the front of my room. This held for LP after CD after SACD after high-res download. A litany of examples would serve no purpose than to make the same points over and over again.

I used the Bia on my Quads, the lovely Harbeth Monitor 30.1s, the fabulous new MartinLogan Montis (review forthcoming), and it acquitted itself superbly on each. My experience with the Montis is limited, but I have long experience with my Quads, and can truthfully say I’ve never heard them sound better. This is the proverbial match made in heaven (and scarcely less so with the Harbeths).

Is the Bia perfect? Well, of course, nothing’s perfect, but no matter what I threw at it, I couldn’t make it sound anything less than beautiful. There may be some other amplifiers that can beat it out for sheer crunch and slam at the bottom, but I’ve no way of evaluating this because I don’t own speakers with very large woofers that may need that kind of control. Current tastes run for more zing, zip, spit, and sizzle up top, though not mine, as I find these things inaccurate and often irritating— sounds the Bia seems incapable of generating. And yet, I know that there is something about the reproduction here that isn’t truly accurate. The complete absence of any sort of negative feedback practically guarantees output impedance on the high side or, equivalently, a damping factor on the low, and this always has an adverse affect on flat frequency response into real-world loads, i.e., speakers. Despite listing a full set of specifications, the Bia’s flyer does not state the figures for output impedance and damping factor, which, in my opinion, Counnas was remiss not to have measured and published.

But listening reveals the effects all the same. My favorite recorded performance of Appalachian Spring is Bernstein with the New York Philharmonic on Columbia. There are many sonic virtues to the reproduction, including powerful dynamics and a clear recording of great spaciousness. But it is multi-miked and notably bright, even fierce throughout the presence region and the highs. On most modern systems, which tend to have rising top ends, the sound can be fatiguing. On a truly flat system, the sound is tolerable, the violins not shrill, but not far off shrill, and in any case have way too much sheen and brilliance. (Every piece in this all-Copland collection is a great performance, but owing to the sonics, I rarely listen to more than one at time.) With the Bia, however, it’s a whole other story. Though the reproduction is plainly bright, it is so smooth and polished, still brilliant, though now silkily brilliant, as to be not only very listenable but even rather wonderful (think of a somewhat overexposed photograph that you manage to correct in Photoshop or Lightroom). It’s pretty hard to be a stickler for absolute accuracy when a component lets you enjoy one of your favorite recordings more than you ever have before.

I’ve already pointed out that the highs are never edgy or hard, which is good, but neither do you have the kind of crystalline ring, ultimate sparkle or tingle, or even the pleasing bite much high percussion can have. This extends to some other instruments too. Sonny Rollins’ sax on Way Out West (SACD and vinyl reissue) is rendered with fabulous body and richness, and even the requisite bite and edge that his tone by design has, yet it still lacks the last degree of those latter qualities I hear from amplifiers that I know to be more literally accurate. I am told this is perfectly consistent behavior from an amplifier that has a highish output impedance. (Harbeth 30.1s have a more extended high-frequency response than either the Quads or the MartinLogans, so they and the Bia are really quite witchy together.)

I should not want to overstate any of this, as the Bia stays within what I would consider acceptable bounds of overall neutrality. But those who love rock and roll, some kinds of jazz or percussion, or any other music that depends for its full effect upon a certain degree of grunge, grit, and rasp would surely want to audition before buying. But, then, you’d have to be crazy to buy any tube amplifier before auditioning, because the spectral profile will always vary somewhat with speaker load in a way that it does not with most solid-state amps.

So where does that leave us? Can a component sound too beautiful? Is accuracy overrated? These aren’t questions anyone can answer for anyone else, so personal is the decision. So many recordings are miked so close to the musicians as to sound at best unnatural and at worst aggressively awful (this is one reason why I still value tone controls, especially for the treble). A design like the Bia poses a real conundrum when it comes to the truth or beauty question. A very close friend of mine, an audiophile of four decades standing, used to love tube electronics and acquired quite a collection of them. Eventually, and in part for professional reasons, he sold them in favor of components that would form a true reference system that would tell him what recordings, including those he makes himself, actually sound like. I invited him over to hear the Bia—he is very familiar with the sound of my system—and his face broke into a smile within just a few minutes. “I can see right away why you’ve fallen in love with this thing; it’s so damn beautiful, so luscious and…velvety. I was in love with sound like this for years, though of course in those days it was nowhere near as clean, low-distortion, or quiet as this, and with nothing of the bass reproduction.” Well, there it is: I freely admit to having become quite besotted with the Bia.

Regular readers of mine will know that judged on the basis of performance alone, I do not find super-expensive electronics to be worth the prices asked for them. By this I don’t mean that they’re not good, merely that they do not in my judgment offer sufficient performance over their lower-priced counterparts to justify the stratospheric asking prices, and sometimes they offer no improvement at all—and we happen to be living in a time of unprecedentedly high performance in even budget-priced electronics. By comparison to the pricing of the most expensive electronics, which can cost as much as luxury automobiles, the Bia’s $12,500 retail is positively modest; but it could be called a bargain only in the crazy world of high-end audio, where wire costs tens of thousands of dollars. By most people’s standards, including mine, it’s still very expensive (another four or five grand gets you an economy car!), and much more than I can justify paying for an amplifier, especially when there are so many available for much less that are more literally accurate.

That said, truth in reporting also requires me to add that the Bia is the only amplifier costing more than $10k that I’ve heard that I might actually consider buying for the sheer love of the way it makes almost every recording I have sound beautiful. It’s not the only amplifier I would ever want to own, especially for reviewing purposes; but if I did own it, I know it would get a lot of use and never cease to be a favorite. This is the kind of design around which passionately enthusiastic cults form, and I can easily see its owners treasuring it like classic Marantz or McIntosh amps from the salad days of high-end audio. I certainly would.


Power output: 60Wpc, 20Hz–50kHz +/-1dB
Speaker outputs: 4, 8, 16 ohms
THD: 0.22% at 1W output into 8 ohms
Gain: 23dB
Noise level: <0.2mV RMS into 8 ohms with input shorted
Tube complement: Matched quad set of four KT88s; four Gold Pin ECC 82s (12AU7)
Dimensions: 17″ x 20″ x 10″
Weight: 66 lbs.
Warranty: 2 years amplifier, 6 mos. Tubes
Price: $12,500

Thousand Oaks, CA
(805) 807-1841

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