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I did not expect any differences. Regardless, I got small ones. The British box had the more acute and lit-up depiction of space but was also coarser and edgier. The Japanese was smoother, calmer and more refined while dimensionally not quite as illuminated. Both were equally adept at the tiny stuff—fingering noises, rain tree tattoos, air escapes from mouth pieces, key clacks, pedal action, tone modulations with their shifting harmonics—to create a strongly intimate rather than distanced observer perspective.

When it came to voices like Dhafer Youssef's outrageous pipes, the slight difference in presentation narrowed itself down to more of a white spotlight for the MFA versus a yellower broader light source for the Yamamoto. The Brit was more pin focused and outlined, the Japanese more broadly focused but less sharp. Knowing Shigeki-San through his A-08S, A-09S and HA-02 amplifiers, his YDA-01 and YDA-01B converters and YS-500 loudspeakers, I think of his house sound as tonally intense, organically flowing, refined and somewhat dense and mellow. As much as a passive volume control can offer leeway to voicing, I dare say that the same criteria have informed the AT-03-1A. Vis-à-vis the TVC, distillates of those same qualities remained.


Practically, the Yamamoto offered more click stops over its range; had the nicer-built enclosure with superior RCA sockets; and at least relative to what the MFA demanded when Walter Swanbon of Fidelis AV imported it for the US, was the more cost attractive. If you're already committed to the Yamamoto sound, there's no reason to go outside. Stick with the brand for sonic congruence and a perfect cosmetic fit.

Going active on preamplification regardless of brand—from Wyred4Sound to Burson to Esoteric in ascending sequence of expense—netted the expected changes for a change. Things got denser, fleshier, fuller and more robust. But in the extremely lucid and microdynamically explosive context of the J2 and Ampeggio, this was subjectively counter-productive at least to my ears. That's because it slowed things down, stepped back attack clarity and luminosity and diminished unplugged rawness for greater coziness. If you will, body enhanced but spirit receded.

I'd be first to admit that unless with transistors one had amplification of rare J2 caliber which manages to combine speed, bandwidth and resolution with exceptional finesse and elegance, chances are that raw and essentially intravenous might not be the top qualities a volume control/preamp should contribute. What's usually required should more fall in line with the acknowledged providence of active preamps: enhanced grunt, deeper colors, more potent bass and overall greater fleshiness. It's probably fair to say that passive preamps aren't for beginners and then only for systems which are deliberately dialled for speed and lucidity over weight and warmth. Lean, mean & straight to the bean could be the mantra of the passive proposition. In the above context, it fit the bill to perfection.

Leaving the best for last (the reunion surprise hinted at earlier), how about the complete Yamamoto setup? I was particularly curious how my very sophisticated and ultra-featured $10.000 Esoteric C-03 preamp—set to zero voltage gain to act as a passive whilst still being energized from 18V rails, display set to show actual dB of attenuation—would compare to the bare-boned AT-03-1A.

To get started, I fitted the A-09S with my customary Emission Labs 300B-XLS. Those are very wide-bandwidth linear modern valves with terrific bass and dynamics but less fluidity and ne sais quoi than vintage-tuned bottles like Full Music or Western Electric. The 5U4G rectifier was another EML, the drivers are non-swappable NOS C3m from the German telephony service of the mid last century.

This proved to be a very interesting game. The differences between preamps occupied more qualitative gestalt aspects than quantitative items down the usual audiophile check list. With the Esoteric, there was more grippiness and innate tension and the subjective stage distance decreased. With the Yamamoto, stage distance increased quite noticeably and the same tension relaxed to become nearly limpid. This shifted my listening focus away from transient angularity and into the more fluidic realm of harmonic shifts and fades. I had encountered a very similar flavor of limpidness before - with Nelson Pass' FirstWatt F4 current buffers whose voltage gain is slightly negative. Something about that innate sense of relaxation is vaguely similar to deep meditation. Certain muscles in the shoulders eventually relax sans volition though one had no sense of holding on to remaining tension layers until after the unclutching. It's vital to be clear that this limpidness was not equivalent to an amorphous state of sounding/feeling like a wet noodle. In formal Zen sitting, the body doesn't collapse either. It simply was all about deep space, rich colors and lyricism over adrenaline.

Once identified and ascertained, this effect welcomed complete immersion in the subtle tonal fragrances which output tube rolling affords. For options I had on hand top glass by Emission Labs, Euro Audio Team, Western Electric, Shuguang Black Treasure, Synergy Hifi and Tianjin. Instead of dynamic tension, I now had the perfect blank canvas on which to optimize tone-color intensity. Isn't that one of the core joys of high-efficiency direct-heated SET systems in the first place? Here Full Music's very expensive new Special Edition bulb quickly proved to be the ultimate choice (full review forthcoming).


This 'change of direction' or listener motivation was unwittingly confirmed by the outright greed whereby I now flew through very specific tracks. They all had in common being down-tempo, very well recorded and uniquely toneful. Be it a slow Vicente Amigo bolero, an Ivo Papasov or Jan Garbarek ballad, Karim Baggili or Titi Robin oud dreams, the gorgeous timbres of Chinese erhu, Turkish qanun, Portuguese guitar or Jai Uttal's dotar on Music for Yoga and other Joys, it was about celebrating maximally rich timbres floating on luminous space. Romantic vocals previously bordering on the schmaltzy—Hassan Issakut on Hayat 1 Hayat, Yannis Parios & Co—became celebrations of beauty, not examples of maudlin sentimentality.

Conclusion: In some fashion, Shigeki-San's new passive box had me rediscover his A-09S amplifier as though for the first time. While anything can be made to—more or less closely—sound like something else, it's an ultimately questionable pursuit. If you favor the more bracing crystalline rush of transistors, yes you can and may bend a 300B SET to your will with ancillaries and glass that pushes general sonics as much in that direction as they will go. Isn't it more sensible though to maximize the sonics around what they want to be naturally? With my Yamamoto A-09S fronted by its new stable-mate volume controller, I suddenly felt deposited into the very heartland of direct-heated triodes. I was indulging their very best virtues and letting them be for not doing other things as acutely (like my favored transistor machines from FirstWatt for example).


If there's anything eight solid years in this gig have taught me, it's that we're blessed with far more sophisticated flavors and perspectives to enjoying fine audio than are commonly acknowledged by the absolutist 'only one way is the right way' dogma. For today, I'd go as far as saying that if you haven't heard a Yamamoto SET with its matching passive volume controller, you haven't heard it fully yet. After many years of ownership, I certainly hadn't truly come to get mine until now. Thankfully it's never too late for new lessons. Yamamoto's AT-03-1A is an absolute stunner with their firm's own amps. Anything else fronting them should likely be a compromise. True, passive preamps very clearly aren't for all folks and all seasons. If you run a SET of Yamamoto caliber however, I urge you to explore this option. You could fall in love with your 45s, 2A3s or 300Bs all over; perhaps even more fiercely than during that first honeymoon. That's where I'm at right now. It's great to be in love again.
Quality of packing: First rate.
Reusability of packing: Many times.
Ease of unpacking/repacking: A cinch.
Condition of component received: Perfect. Owner's manual reflects the website descriptions and suffers from software generated Japanese-to-English translation.
Completeness of delivery: Perfect.
Human interactions: Always prompt, courteous and forthcoming.
Pricing: Somewhat on the high side.
Final comments & suggestions: Zero creature features. 3A model adds input switching and a second set of RCA outputs. These are ultra purist machines particularly optimized for the high-gain noise-sensitive direct-heated amplifiers of the same company. Arguably the ultimate fit with them but not necessarily translatable to just any system. As reader Joseph Pagan found out, "... in my exploration of passive preamps I've found that running an interconnect post attenuator is often much more detrimental to the overall sound that one might assume." Joseph ended up with no cables at all compliments of these Ultimate Attenuators from TweakAudio. The upshot is, keeping one's cables between passive and power amp as short as possible is probably a very good idea.
Yamamoto SoundCraft website