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Reviewer: Srajan Ebaen
Financial Interests: click here
Source: 1TB iMac with AIFF files via FireWire 800 into Weiss DAC2, Yamamoto YDA-01
Preamp/Integrated: Wyred4Sound STP-SE, Esoteric C-03, Burson Audio Preamp 160, Music First Audio Passive Magnetic
Amplifier: FirstWatt J2 & F5, FirstWatt M2 [on review], Trafomatic Audio Kaivalya, Yamamoto A-09S, ModWright KWA-100
Speakers: ASI Tango R, Voxativ Ampeggio [on review]
Cables: Complete loom of ASI Liveline
Stands: ASI HeartSong - 2 x 3-tier stands, 2 x amp stands
Powerline conditioning: 1 x Walker Audio Velocitor S, 1 x Furutech RTP-6
Sundry accessories: Furutech RD-2 CD demagnetizer; Nanotech Nespa Pro; extensive use of Acoustic System Resonators, noise filters and phase inverters, Advanced Acoustics Orbis Wall & Corner units
Room size: The sound platform is 3 x 4.5m with a 2-story slanted ceiling above; four steps below continue into an 8m long combined open kitchen, dining room and office, an area which widens to 5.2m with a 2.8m ceiling; the sound platform space is open to a 2nd story landing and, via spiral stair case, to a 3rd-floor studio; concrete floor, concrete and brick walls from a converted barn with no parallel walls nor perfect right angles; short-wall setup with speaker backs facing the 8-meter expanse and 2nd-story landing.
Review Component Retail: ¥ 198.000
One could rightly regard Yamamoto Sound Craft Corp.of Japan as one of WE's contemporary spiritual heirs. Western Electric was the precursor to AT&T Technologies even though valve lovers today relate to the name mostly for their 300B. During its halcyon days, Western Electric had some 2000 employees as does the Kudelski Group today. Meanwhile the Nagra Audio division inside the Kudelski Group accounts for a mere one percent of that number. That's a realistic mirror on high-end audio's niche role. Yamamoto's employee ranks might be slimmer still. But when it comes to a modern audio firm which applies direct-heated triodes to minimalist single-ended circuits of micro power output in the vein of classic movie-house amps from the Golden Age of tubes, Shigeki Yamamoto's team is one of just a few who uphold that legacy.

Fond of high-gain driver bottles like the German telephony C3m used in my A-09S, Shigeki-San's amps in general don't require preceding voltage gain when used with copasetic speaker sensitivities and modern high-output sources. This opens the doors to passive preamps which won't amplify AC heater noise but merely step down amplitude below unity gain.

Two new Yamamoto boxes address that very scenario whenever digital-domain attenuation is considered inferior. Named AT-03 for attenuator, the model 1A is a single i/o affair, the model 3A the three-input twin output equivalent. The 1A offers no source switching. It's but an in/out loop with a 27-position Seiden 45SD switch. On each step, that rotary switch is fitted with one ultra-precision 1-watt surface-mount film resistor from US supplier Dale. It becomes a high-quality L-pad volume control to present a constant output impedance regardless of setting. The model 3A adds an input selector and paralleled output. 6N copper wire of 1.2mm diameter and sheathed in Teflon connects the RCA sockets to the vertical mini PCBs with the attenuation resistors. The signal path is kept as short as feasible. This minimalist passive circuit is housed inside a 2mm stainless steel chassis. Trademark champagne-anodized aluminum panels surround it, then the whole is dressed up with solid Japanese Cherry cheeks. Ebony knob/s and Ebony footers round out the accoûtrements. Either box measures 200 x 270 x 97mm WxDxH, weight is 2.2/2.5kg respectively. The input impedance is a friendly 50K, the attenuation range spans from - 65dB to -38dB in 3dB increments, from there to 0dB in 2dB steps.

Like anything Yamamoto, this product is about purity. While particularly transistor listeners often demand active line stages for proper tone and dynamics, SET lovers with ideal amp/speaker marriages routinely do not. They instead want a basic volume control with ultimate neutrality and zero noise. At $10.000, my Esoteric C-03 preamp provides comprehensive remote convenience, RCA/XLR i/o ports and switchable gain including zero. The latter turns it into a passive preamp, albeit of the sort that still runs off 18V rails. For $2.000, there's the Wyred4Sound STP-SE. It too operates as an activated passive until its relay-switched resistor ladder volume control exceeds unity gain to summon up an active gain boost. And for roughly €1.800 there's now the Yamamoto AT-03-1A. Minimalist to the extreme, it categorically removes the input switching of the bigger boxes, reduces their outputs to just one and eliminates remote-controlled creature comforts. Is this a raw deal or precious ultra purity?

I had four comparators to decide - Burson Audio's 160-Series preamp, the earlier mentioned Wyred and Esoteric pieces and another true passive, Music First Audio's original Passive Magnetic. The first three are universal preamp designs. They're intended to work with all types of hifi systems. The pots in boxes transformer volume control from the UK and the L-pad from Japan aren't. They require just the right kind of context. The relevant question is, would Yamamoto's passive be preferable when one had this context?


I'd mock up it up with Yamamoto's very own YDA-01 D/A converter and A-09S 300B SET. The joint gain of this combo well exceeds all my listening requirements. The amp/speaker pairing of Yamamoto and speakers meanwhile exhibits a very precise flavor. Most would not desire to enhance or alter it in any way. With the only thing missing from this picture an essential means to control volume, might an audible nothing not be better than any prospective something? That shall be our version of Hamlet's famous question for today.