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With a nice fat exclamation mark, the A-09S instantly lived up to my contrarious hopes - of not being yet another 300B single-ended amp cut from the usual cloth. In fact and perhaps perfectly predictable after the fact, this one is far closer to the aural aesthetic of Shigeki-San's A-08S. In many respects, it clones the EML solid-plate 45 aroma and grafts it onto the 300B. With the very same pair of Western Electrics, my Woo Audio Model 5 sounds quite different. I'm thus inclined to believe that it's thicker, slower, sweeter flavor -- in short, more of what most tend to think of as 300B-typical sound -- is due far less to the actual 300Bs and far more to the Wooists' choice of 6SN7 drivers. In many quarters, these particular octals are equated with luscious tone. In the Model 5, they clearly contribute also to a higher degree of fuzz and fluff. Call it a modicum of push/pull girth. Or the use of a somewhat fatter brush with not as finely twirled a tip to render the scenery. A dose of voluptuousness if you will, of floral perfume. The big Yamamoto cleans house there. It banishes most of those enhancements which, I'd imagine, its 45 stable mate would consider cob webs in the belfry.

Note I said most. The A-09S doesn't simply quadruple power to otherwise sound exactly like the A-08S 45 amp. Why make chicken taste like turkey? The O-Nine gets surprisingly close yet remains fleshier and not quite as lit up. For those who find the 45 too stripped of romance, too energetic and lean, the 300B sibling makes a small concession of saturation and wetter textures. But those attributes are subservient to the dominance of Yamamoto 45 values and a function too of just what 300B you roll. True regardless is intensely holographic soundstaging, keen clarity, advanced directness without quite the crystallization of the 45s and highly developed tone colors (those go beyond the 45s). This is no 300B amp that'll kowtow to Jacintha, then suffer castration at the hands of Zawose's & Brooks' juju, Daara J's fresh Senegalese rap or Renaud Garcia-Fons' wiry bass frenzy. In fact, that whole smoky nightclub seduction thang is very much reined in. This seduction is all about the intensity of transmission sans smoke and shadows, sans subliminal haziness and soft focus.

Drive and gain of the A-09S are unexpectedly potent, proven when I leashed up the broad-shouldered red deck to the 91dB DeVore Fidelity Nines. At 2:30 on the 12dB-gain ModWright's dial, these speakers acted ballsier than on a number of higher-powered amps. Go figure. Not belonging to my hi-eff club of speakers with active bass systems, the Nines could take the measure on bass directly. With the WEs, amplitude was quite buxom but the character -- on these speakers whose dual-ported dual-woofer'd alignment fancies more damping -- was just a bit loose and bloomy. Depending on material, this fluffier, less tensioned behavior, to a more subdued extent than in the bass, held steady also across the board. It telegraphed, for all my harder-hitting stuff, the silent desire for a somewhat tighter fist. Swapping in the stout EAT 300B Diamonds from Jozefína Krahulcová's Czech Euro Audio Team plant showed how sometimes, a book can be judged by its cover. With more robust construction than the Western Electrics,
thicker bigger glass (66 x 16mm), nicer pins (gold-plated to boot), her valves not only look and feel more substantial and weightier, they sound it when slamming club beats demand current and grip to crack hard and sharp like a whip.


And yes, you'll lose a dose of rubato - that inter-note flexibility of the 'Chopin factor'. The beautifully made Czech valve is rhythmically more gathered up. It's unwavering, driven and definitely more sorted when it comes to low bass fundamentals and overall articulation. For the majority of my favored world music fare -- peppered with rhythmic complexity and often low bass -- I prefer the EAT. The WE does however have ultimately more timbral finesse particularly on massed strings. The EAT meanwhile has the edge on, say glockenspiel accents and qanun quivers for that crisper, livelier jump factor that peels out cleanly from the surrounding fabric. One flavor is more about decays, harmonics and watercolor transitions; the other about transients, rhythmic elan and clear separation. Naturally, that's a matter of fine degrees, not clash of religion.


In today's auto-bias amp, the EATs are also quieter. Explained Shigeki Yamamoto: "The A-09S's DC heater circuit uses a small 2200uF capacitor instead of the usual 10,000uF value. This is better for the life of the output tube since inrush currents are reduced as well but also means that residual noise levels will depend on just what kind of 300B is chosen. This level will fall between 0.5 and 2mV due to the heater circuit configuration." The EATs, ears on the DeVore drivers, were essentially inaudible. And because the 91dB DeVores aren't exactly speakers I'd consider ideal for any 8wpc 300B SET -- I'd like to see more muscle and damping on the bass drivers, more headroom to operate the triodes deeper in their sweet spot -- the fitter, stronger EAT valve was superior in this context. Moving into fully optimized 300B territory which some might call idealized but it really means the same, the DeVores soon made room for the Zu Audio Presence loaners.


My smaller 2wpc Yamamoto, which had essentially gotten married to my Definition Pros so good is the combo, had no SPL issues with the Presence. Yet despite the new 16-ohm widebander, it was lacking just a bit of pop and pressurization in that driver's lower band of the upper bass. Much of music's communicative elan and energy live in this 80-250Hz range. With the A-09S, those concerns were no more. This became one of those unplanned combos that just kick royal arse. Everything aligned. Major dynamics and jump factor. Very vibrant tone. Superb projection power across the room into the listening seat. That doesn't mean forward staging. It describes how the sound reaches for you rather than hovers somewhat listless back there behind the speakers, demanding that you retrieve it. Not here. Plus, the dual 10-inchers per side, sealed and driven from their own Hypex-powered amps, categorically declared even the best no-feedback low-power SET bass compromised by comparison.

Bands refer to their percussion and bass section as the engine or boiler room. It's where the momentum and pressure for the tunes come from. Superior bass is a requirement if you want your music to be intense. But without tangible image density and tone, you'll just have relentlessness. This combo does tone, rhythm and body exceptionally well. It sounds loud and real even at low levels. Picture your heightened emotional response to rock-out sessions when the neighbors are gone. Then apply the same intensity to when the neighbors are back again. It's in that sense the Yamamoto/Zu combo sounds loud even when it's not. It's what superior single-endeds excel at if properly speaker matched. What proper means depends on experience. If you've heard a proper matchup at least once, it lets you know when you're not getting the full measure. Especially newbies coming from drier flatter transistors tend to be too easily impressed. Don't sell yourselves short. If a low-power/hi-eff combo doesn't communicate its virtues instantly, something's amiss. When right, this stuff is far from subtle.


The Yamamoto has high gain to drive my DeVores to high levels in my digs. However, attainable loudness and ideal matching aren't synonymous. Once you hear what the Red Wine Audio Signature 30.2 does on the DeVores, you'll recognize where the Yamamoto falls a bit short in certain aspects. 30 watts of high current and low output impedance do make a difference into a 91dB passive load. Conversely, once you hear the Yamamoto on the partially active 101dB 16-ohm Zu Presence, you'll recognize how here, it has superior textures, stronger tone colors, more transmitted energy and more dimensional staging over the Tripath. Superior and better are very relative. While the A-09S' high gain seems copasetic with 91dB speakers -- for SPLs, it really is -- the special magic enters at higher speaker efficiencies (and yes, phase angles and impedance fluctuations factor there as well). The unusually robust and burly showing of the EAT-equipped Yamamoto can simply confuse the issue that any of these triodes unfurl their petals most fully when not asked to leave the first watt. That figure is metaphorical. I don't know the precise percentage of peak power which constitutes the perfect load line or sweet spot for a 300B. Rising distortion figures show that running DHTs in the low range of their top power rating always makes for superior results. Just because this amp is uncommonly stout for the breed doesn't mean you should leave the reservation. Instead of getting some rays where the 300B sun usually won't shine, get the full illumination with speakers 95dB and up. At least that'd be my generalized advice.
Intermediate conclusion
I have a few perennial test tracks for certain qualities. One is "Balkan Blues" on Nedim Nalbantoglu's Yeni Dünya album [Park Muzik]. This is high-octane frenetic stuff that walks a very precarious high-wire act between wilting your nerves or hypnotized fascination. The basic configuration is harmless enough - an acoustic quartet of violin, guitar, accordion and percussion. Except "Balkan Blues" uses a fast asymmetrical odd-metered rhythm and violin virtuoso Nalbantoglu scrapes steam off his strings with furious Jazz-influenced riffs and runs. The energy boils without letting up, the drummer delivers complex rolls and trills without stopping, the accordion does those jagged chromatic speed runs Bulgarian rutchenitsas celebrate and you're either pushed into a mindless state of pure marvel over the complexity and virtuosity on tap; or you shut down feeling relentlessly assaulted and hammered.
The question this track inspires during testing is simply, how far can a particular component combination push the raw energy element before the gig flips to become annoying. Those who continue relating SETs to lounge singers won't believe how this Yamamoto aced the super-spicy 3N Noxious Nalbantogulu Nerve rattler challenge with a higher score than most powerful pull-pull valves or transistors. It requires dancing on the edge of blistering transients and tight timing while fully developed tone and densely sculpted images perform the balancing act. Speed and substance. If by warmth we mean buffered edges and a certain languidness, attacks and forward drive soften. If we fade colors, the leading edges take over to become assaultive and the violin in particular becomes hyper metallic and scratchy. If we sweeten the stew by contouring the treble, the cayenne action right on the string gets diluted and the excitement tones down. Like a spider web, all these elements are interconnected. Specific qualities turn out to just be different aspects of one another.


On the Presence speakers, the Signature 30.2 is sweeter, warmer and slower to tame down this particular track. The A-08S is a bit leaner and also creates more upper-midrange fire to 'flip' sooner. In short, for immediacy and adrenaline (speed and timing) coupled to comfort (tone), the A-09S allows me to listen to my most unplugged uncut fare whilst getting the biggest hit of spice and energy. Naturally, that description doesn't conform to populist notions of 300B SETs. Which neatly segues back to the head of this page. Shigeki-San's new reference amplifier retains the famous tone of the 300B tube but strips away most (but not all) of the attendant 'prettifying' THD filter action. This machine does both speed and intimacy. The following two pages inspect how performance can be tweaked with tube rolling.