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Reviewer: Srajan Ebaen
Financial Interests: click here
Source: APL HiFi NWO 3.0-GO; Ancient Audio Lektor Prime; Raysonic Audio CD-168
Preamp/Integrated: Supratek Cabernet Dual; ModWright LS-36.5 with PS 36.5; Wyetech Labs Jade; Almarro A318B; Melody I2A3; APL Hifi UA-S1; Woo Audio Model 5; Yamamoto HA-02

Amp: 2 x Audiosector Patek SE; 2 x First Watt F4, 1 x F5; Yamamoto A-08s; Fi 2A3 monos; Yamamoto A-09S;
Speakers: DeVore Fidelity Nines; WLM Grand Viola Monitor with Duo 12; Rethm Saadhana; Mark & Daniel Ruby and Maximus Monitor with optional OmniHarmonizer; Acoustic System International Tango [on review]; Neeper Acoustics Perfection One [on review]; JohnBlue Audio Art JB8 [on review]
Cables: Ocellia Silver Signature loom; Crystal Cable Ultra loom; Crystal Cable Reference power cords; Stealth Audio Indra and Meta Carbon; Acoustic System International Liveline [on review]
Stands: Ikea, with re-purposed Ikea butcher block platforms
Powerline conditioning: 2 x Walker Audio Velocitor S fed (from custom AudioSector 1.5KV Plitron step-down transformer with balanced power output option for 120V gear)
Sundry accessories: Walker Audio Vivid CD cleaner; Walker Audio Reference HDLs; Furutech RD-2 CD demagnetizer; Nanotech Nespa Pro; extensive Acoustic System resonator tuning throughout the house
Room size: 'Elephant Cave' sound platform 3 x 4.5m with 2-story slanted ceiling; four steps below continues into 8m long open kitchen, dining room and office which widen to 5.2m with 2.8m ceiling; sound platform space is open to 2nd story landing and 3rd-floor studio; concrete floor, concrete and brick walls, converted barn with no parallel walls nor perfect right angles; short-wall setup with speaker backs facing the 8-meter expanse
Review Component Retail: ¥ 228,000 (¥ 178,000 in kit form); $2,450 in the US

In these pages at least, Shigeki Yamamoto has developed quite the reputation. I own his A-08S 45 and A-09S 300B SET amplifiers as well as the HA-02 headphone integrated. And I consider each of them one of the best of their kind and price. A quick finger walk into our archives (try the alphabetical listing under 'Y') will give you extensive background on the company. Here we'll simply say that Yamamoto Sound Craft from Japan has championed analogue for 15 years with tonearms, cartridges, a phono stage, plenty of low-power valve electronics and Altec-inspired widebander speakers to finally hit the apparent cross road: digital and transistors.

Charmingly perhaps, Yamamoto is just catching up to the fact that CD is the last, most entrenched software medium remaining. That the world has turned a few more revolutions since to want to abandon music carriers in favor of downloadable files for magnetic streaming is presently not their concern. What is? "Digital lacks grace." The plainly named YDA-01 -- Yamamoto Digital/Analog converter #1 -- is Shigeki's answer. To keep things affordable, he eschews balanced connections to provide just one RCA input and one pair of RCA outputs (the lack of USB is for simplicity's sake especially in the parallel optional kit). To strip back further complexity, he eschews valves too. But it'd not be Yamamoto's style to settle for the norm. Shigeki San's research and listening have him convinced that digital's lack of grace must point a wagging finger at the customary current/voltage conversion and output stage implementations - more so than the chosen hardware of digital chicanery. As an analog man, it's not surprising how that part of the converter's circuit would command his raptest personal attention and core expertise.
He dislikes unnecessary gain stages. In particular, he regards hi-feedback operational amplifiers with grave suspicion while freely acknowledging their test-bench specmanship. But then, Shigeki's love affair with tubes had him long since transcend justifications for measured perfection. His experience tells him that just a few dB of feedback compromise the sound; and that simpler circuits always sound better than more complex ones. His overriding concern for the YDA-01 was how far down circuit simplicity could be pared while still operating properly. The return of grace showed the path forward.

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As the earlier block diagram hints at, the dual-differential stereo output of each PCM1794A (which includes the digital filter) is converted to mono by summing one phase and shunting the other. This twinned current output couples to the emitter of a single metal-encased PNP transistor while one intermediary load resistor handles I/V conversion in place of the usual op-amp. There's no applied feedback anywhere. A CS8416 digital receiver chip automatically locks to incoming 32 to 192kHz data and feeds the properly loaded twin DACs into the minimalist, single-ended transistor output stage without phase inversion. Nine discrete regulated power supplies (three for the 8 x upsampling CS8416 stage, two for each PCM1794A and one each for the monophonic output stages) hover in close proximity to their respective charges to lower operative impedances and avoid power supply interference. The secondaries of a 150VA wood-covered toroidal power transformer with silver-plated copper turns -- the iron considered to be overspec'd by a factor of 5 for the given application -- provide the regulator voltages. Quipped the maestro: "Power supply quality is absolutely critical for amplifiers and preamps. D/A converters are no different." The recipe is simple circuit, overdimensioned power supply.

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The fewer-but-better parts credo for the signal path manifests in OS Con mica and poly-film capacitors, Dale resistors and ebony-sleeved output coupling caps. As expected, there are also Yamamoto's own bronze/Teflon connectors plus the trademark resin-impregnated Shashi Cherry wood on the enclosure's cheeks. Besides the turn-key converter, there's a kit version with prefabricated digital chip boards to focus the DIYer's duties on the output stage (which then could sport valves). A custom board with a hot-swappable (socketed) OPA627AP will also be offered for those wanting to roll op-amp chips. A-weighted S/N ratio is 86dB, output impedance 2.6K, weight 5.2kg. Dimensions are 420 x 290 x 94mm WxDxH. At 3.1V/0dB, output voltage is higher than standard digital sources.

Added Shigeki-San: "The YDA-01 is the first D/A converter for us. Many CD players and DA converters are sold all over the world. We hardly know about those products. Therefore, there is no telling what kind of status our product will occupy when being compared with them. However, we have remarkable confidence in the sound quality of the YDA-01. In Japan, the YDA-01 just began to receive coverage by the domestic audio magazines. The response in general has been good. The output circuit of our YDA-01 consists of one transistor without feedback. I think that circuit implementation is novel and hasn't been attempted before. The great feature of this extremely simple circuit is its impact on the sound. Although I am not personally a specialist in digital circuits, our employee assigned to that part of this project very much is so even there, we are quite confident."

This was in response to submitting my list of would-be comparators, from sub $2,000 Opera Audio and Raysonic machines to a $10,000 Ancient Audio champ and a $35,000 APL Hifi/Esoteric state-of-the-art flagship. When being solicited for reviews, it's sporting form to warn manufacturers upfront. Some then withdraw which tells its own story. Shigeki-San's confidence was inspiring, particularly in light of his $2,264 Japanese base price (converted via October 12 exchange rates; Yamamoto leaves end-user pricing to its foreign distributors since they must deal with various regional VAT and import tariffs as well as currency offsets, all of which influence the final sticker). My hardware gallery of digital sources presently includes no outboard D/A converters. As a genre, non-USB-equipped DACs have dwindled. Plus, the jitter potential of the digital send/receive interface isn't compounded with one-box CD players like the Abbingdon Music Research CD-77. You might say that the timing of this product's launch is peculiar. With a USB input of course, it'd be very timely again. Shigeki-San did indicate that an eventual "high-end version might incorporate it".

Such are the shifts and turns of audio fashion. If you've read this far, we'll assume that you've kept the faith with conventional CD playback; that you could be interested in upgrading your digital-out fitted machine while retaining its solid transport facilities. If the YDA-01 offered a substantial improvement hung off my Raysonic Audio CD-168 for example, there'd be justification to spending this type of money on a standalone DAC (and converting your existing CDP into a transport) rather than going after a same-priced new RedBook player. My main interest in this assignment wasn't at all tied to the component's market potential. That's always the manufacturer's burden, here more so than usual. I wanted to know
what a musician's ear like Shigeki Yamamoto would do in this category. I've always found his components to offer exceptionally persuasive performance - besides being beautifully built and fairly priced to deliver the whole pride-of-ownership package with a bow. The issue of missing grace in digital; and the promise of solving it in this price sector... well hell, I simply had to check this out!

Shigeki then made a final point: "We strengthened the power supply to pull out the power of the bass region. Powerful low frequencies in the true meaning of the term cannot be expressed merely by widening the frequency response. It must occur by painstaking design of the power transformer and regulator circuit. Although we had an opportunity to hear some DA converters by other companies, they all lacked this true foundation power. I think that our YDA-01 here is particularly excellent. In conjunction with a good power amplifier, it should demonstrate the true force of a recording's low-frequency region." I was ready. As I'd find out, so was he...