Zesto Audio Andros PS1 Vacuum Tube Phono Preamplifier

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Equipment report
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Phonostages
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Zesto Audio Andros PS1
Zesto Audio Andros PS1 Vacuum Tube Phono Preamplifier

 “These guys got a lot of things right, even though their tools were slide rules and trial-and-error.” He claims some 71 circuit revisions and hundreds of parts upgrades before he arrived at the production Andros. Paying as much attention to the outside as the in, Counnas enlisted the help of his wife Carolyn (an artist) and Musky Mistry (an industrial designer) to come up with a look both unusual and unusually pretty. The black chassis consists of a lower layer adorned with a grey graphic of undulating curves on the fascia. The upper layer is shaped like a grand piano (viewed from the top) with a mirrored finish on the front edge that reflects the four softly glowing tubes located within the hollow curve. The graceful, gently curvy style belies the ruggedness, the chassis made from 16-guage steel and supported with IsoNode isolating feet. Parts quality and workmanship appear first-class.

The PS1 will accept both moving-magnet and moving-coil pickups (you can hook up two complete phono setups, provided one is high output, the other low), and there are even balanced inputs to parallel the RCA inputs (but RCA-only outputs). There are a two-position level switch for MCs and a novel grounding switch that allows you to isolate the ground if need be. Of great importance to me, Counnas is most definitely not a subscriber to the one-size-fits-all approach to loading, the PS1 offering eight options from 20 to 1000 ohms. Technical specifications are impressive, the price is $3900 (which includes 50 hours of factory burn-in), and each unit is “hand-built in the USA.”

As the Zesto factory is not far from where I live in Los Angeles, the Counnases themselves delivered the unit and set it up, though there was hardly any need for this, so easy is the job, out-of-the- box to music taking scarcely fifteen minutes. There is literally nothing to do but plug it in, attach all the appropriate signal cables (not provided), select pickup type (and loading option if applicable), turn it on, and put on a record. Since the unit is burned in at the factory, you might want to give the tubes fifteen or twenty minutes of warm up if you want to hear the Andros in all its glory the first time you cue stylus to groove (about the same warm-up time is required after it’s been off for awhile). Once you recover from the sheer beauty of that initial sound, what may strike you next is how quiet this thing is, noise being one reason for my bias against tube phonostages. No, you cannot crank the volume all the way up with your ear right against the speaker and hear silence (you can’t do that with most solid-state phonostages, either). But unless playback levels cross over into the insane, the impression of background blackness is without precedence in my experience of tube-based phonostages.

At the outset I said I believed there are good technical reasons why this unit sounds as it does, reasons not unrelated to that impression of low noise but not necessarily related to the use of tubes as such. Rather, I believe they have much to do with Counnas’ decision to use transformers to step up the low- output moving-coil signals. It has always surprised me that so many phono preamp designers eschew transformers in favor of active stages. To begin with, transformers are passive and do not generate electronic noise, which makes them, all other things being equal, quieter than even solid-state circuits, including those that are battery-powered. They are also far more tolerant of the vagaries of loading than active stages and suppress the resonances endemic to all moving coils much more effectively. Although some transformers are very expensive, there’s little evidence to suggest that they must be so to do their job effectively—design know-how definitely trumps exoticism of parts and materials.

Detractors of transformers will insist that they ring and that by comparison to active stages tend to be midrangy, with the frequency extremes suffering (highs rolled, bass soft or down in level), likewise dynamics, transparency, resolution, and “speed.” Those of us who like transformers grant some of these shortcomings as regards units of less than competent design but counter that none of them is intrinsic to the technology. We would also argue that transformers yield a more natural, musical, and altogether pleasing sound than any active stage.

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