Digital Do Main - Sound Quality

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FET amplifiers of various flavours I have heard came across as dry in delivery, almost prim and proper and very much of the solid-state breed. And, broadly speaking, the B-1a is in this mould, although it is obviously a highly refined hi-fi product of its time, by which I mean that attention to component quality all through gives it a sense of being consummately well preened for its purpose. FET amps of the 1970s were nothing like this, mainly because apart from their V-FETs, general component quality was poor, as with other amplifiers of the era, and this compromised both clarity and precision.

The most striking feature of the B-1a I felt was a sense of intense insight and detailing quite beyond the almost - by comparison - approximate sound stage set up by modern transistor amplifiers. Dry in nature and constrained in a way a valve amplifier is not, the B-1a was at the same time intensely insightful, bringing a spotlight onto vocals that revealed every little inflection and nuance of delivery, as well as all the production details within the recording that act to enhance a studio recorded performance.

Gabrielle's usually warm, dusky tones in 'People May Come' almost crackled at me as information in the midband and upper midband jumped from our Spendor S8e loudspeakers, projected forward in megaphonic fashion. Her own backing harmonies also leapt out and the smallest fades and echoes used to add depth and embellish the recording all became intensely etched and very obvious. The only reservation here came from a diminution of warmth and body, from a singer whose vocals rely these qualities


The 2sk77b output device, a vertically arranged static

induction transistor designed for audio.

Do you think Hugh Cornwell has a strong, deep but almost rasping voice as he heads The Stranglers? Well, the B-1a makes more of all the tiny details that make up his vocal delivery rather than standing back and presenting a singer whose delivery suits his idiom. In this the B-1a's sense of analysis can detach content from performance slightly, at least until you acclimatise to it. I would describe the B-1a as more academic than atmospheric in basic character, but that it can get so much out of a recording where others seem to struggle suggests it has a lot going for it; it's just this amplifier puts it all together differently.

The B-1a is astonishingly forthright and peers right into a performance, pulling it apart with cool precision. Grippingly concise, it places every fine detail into place in the acoustic picture with military precision and, by way of contrast, makes normal amplifiers sound quite vague, both spatially and temporally. Although that makes the B-1a impressive rather than romantic, its abilities are obviously quite beyond the current norm and there were some fascinating consequences.


A single B-1a can be set to bridge mode (single

channel) to double power. Channel level controls are provided,

as well as balanced and unbalanced inputs.

One feature that intrigued me was that its intensity and precision resulted in a conspicuously well ordered sound stage on which instruments seemed to have a more forceful locational presence than I have heard before, so a cymbal would ring from just there - a point in space no bigger than a 5p piece 3 metres distant! This seemed to be a function of both the drily wrought, forcefully projected nature of instruments, as well as vivid insight into their character that made them seemingly closer. There's no doubt also that great midband and upper midband presence helped toward this effect and here I suspect the step down transformer was not helping by lessening bass impact, reducing emphasis of low frequencies.

However, I have to say that the B-1a has the sort of tightly ordered delivery of a high feedback amplifier and its enormous damping factor was holding back even our usually quite loose sounding Spendor S8e loudspeakers. As expected, the more I turned up volume the better it all got, bass coming across as viciously tight and impactful, if dry as a bone.


A guard wheeling in the weighty B-1a in its flight case, after the Audio 09 show at

Whittlebury, where it was on display.

There was a small but obvious de-emphasis, as it were, of upper treble that at times made the delivery almost creamy smooth in balance – until that is my attention was yanked back to the blare of a trumpet, the crash of cymbals or an attention grabbing vocal delivery much closer to my ear than I am used to. Not only does this amplifier possess clinical precision, it really does see into music and dynamically support it across midband and treble.

As usual, the taut bass of a high damping factor amplifier is a mixed blessing, yet with the right loudspeakers - and Tannoys come to mind - having prominent and deep bass, an amplifier like this might be just the ticket. With the Royal Philharmonic playing Tchaikovsky's 'March Slave', for example, all the emphasis was on the upper registers, yet when the tubas took up the slow main theme it sounded suitably hearty and physical, razor-sharp timing bringing precision that didn't go amiss. Violins interjected repeatedly with precise timing, stabbing into the sound stage with attention grabbing force.


Whimsically comparing pianists John Ogden with Volodos after someone had insisted the latter was a great player (technically true... but I prefer John Ogden's more romantic style) I heard barely a trace of the piano's body. Although both recordings I listened to were themselves short on low end information from the piano, probably due to microphone positioning, this amplifier does nothing to tease out information from the lower end of the musical spectrum. Yet at the same time, strong plucked bass rolled along solidly to provide a cheeky support line behind Amy Winehouses's 'You Know I'm No Good', and kick drum had a nice tight thud to it. Both seemed to reach downward without constraint and here the B-1a benefitted from its all-direct coupled design I suspect, our measurements showing it reaches down to d.c.

Over a few weeks of use with a variety of loudspeakers the B-1a remained consistently impressive, being both concise and revealing to a degree that is the hallmark of true high end. This is a highly developed and specialised product, that's obvious when listening to it. It does, however, need appropriate matching loudspeakers and here life may get a little tricky. Princesound Prince II electrostatics may be one choice, having complementary insight and also a need for high power (well, voltage swing). Tannoys like the Definition Series DC8s or 10s would match character-wise, even though they don't need the power of the B-1a, unless you have a baronial hall full of merry souls to amuse perhaps. The B&W CM9s I review in this issue worked quite well, the B-1a's slow roll down in upper treble acting to damp their treble unit just a tad, whilst their nicely balanced bass of good quality strengthened upper bass from the amplifier a little.

Vinyl LP also proved a nice match, although I felt a need to step up from an Ortofon 2M Black to the moving coil Cadenza Bronze to gain transparency, then quality cuts like Mark Knopfler's 'Punish the Monkey', from the album 'Kill to Get Crimson', sounded wonderfully tidy and poised, guitar strings displaying a firm, cutting twang, hand drums having substance behind the outline of their sound. Knopfler's voice was starkly clear centre stage, gloriously fleshed out with fine detail, enunciation highly specific as a result.


The B-1a basic circuit topology, with phase splitting and gain from two differential pairs,

and one pair of N Channel 2SK77 output devices. The amplifier is all direct coupled.

Not shown here are protection circuits, servo circuits, power supply and suchlike.



Digital Do Main's claim that this is a unique amplifier from a company that believes its products can go down in (Japanese?) history as classics possessing assured value (it's all in the company's founding documents, and why Canon invested), I completely believe. The B-1a is quite an amazing amplifier based on the unique technology of the Static Induction Transistor, developed in Japan and little known or used elsewhere. Likened to the triode valve in operating characteristics, in the B-1a amplifier it finds a suitable home. So like the original Yamaha B1 V-FET amplifier, the Digital Do Main B-1a is a unique and advanced design that is flawless in what it does.


The Yamaha B-1 MOSFET amplifier from 1974, after which the Digital Do Main B-1a is named.

Our 100V factory sample from Japan I suspect does not fully represent what a final 240V model will sound like. Forgive me for pleading with our editor DP to phone Hamamatsu straight away to get a sample, but on this magazine we have a lot of respect for product from Japan. And what Dr Nishi told me at the High End Show in Munich, and what I read on the info CD he gave me, was enough to make reviewing this product a must. The B-1a is a very special amplifier and when UK samples arrive at importers ABC Audio, if you have the money and inclination it is worth a close audition. Their deep clarity and sense of ordered precision will I suspect make many rivals sound quite vague and win hearts.


verdict five globes

Unusual and highly advanced power amplifier using special FETs, the B-1a is wonderfully detailed and concise.


ABC Audio

+44(0) 20 8462 1379


- midrange insight and detail

- strong imaging

- beautifully built


- awkward proportions

- overly tight bass

- no remote volume



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