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Where tubes and transistors meet
I've enjoyed some intense recent comparisons between the FirstWatt F1, F2 and Taboo amps to pen first listening impressions on Nelson Pass' latest transconductance amp. This neatly served a dual purpose - to get at the core signature of the Taboo. These same listening sessions also kicked off a parallel 3-part industry feature on S.E.T.s (I, II & III) that was inspired squarely by the Decware SEP's failing to conform with certain old-timey notions about single-endeds.


In short, if superior transparency and blazing speed with just a skoch of sweetness were your definition of neutrality, it's remarkable how similar realization of this purpose can be regardless of whether you employ transistors or tubes. The 5wpc no-feedback single-ended solid-state amp from FirstWatt and the 6wpc adjustable feedback single-ended pentode amp from Decware are grown from identical root stock and then diverge only subtly, with the transistors enjoying one advantage, the tubes another.
Neither amp sounds recognizably glass or sand though much of that is admittedly a function of expectations and exposure (these lines have gotten blurry not just yesterday). Nelson Pass and Steve Deckert have kept themselves deliberately out of their creations as it were. There's no recognizable voicing beyond what -- based on the simplicity of these circuits -- is a function of the output devices, the applied bias and so on.


Put differently, both amps are essentially neutral (or devoid of clear interpretive slants) but not identical. The predominant area of overlap is clarity, directness, resolving power, treble elegance and timing accuracy whereby percussive events are crisp yet not strident, incisive yet not hard.
Forget warmth, laziness, voluptuousness, darkness, softness, romanticism or overt density. Those attributes can be attained either by strapping SETs to unfavorable loads that will elicit plenty of loudness but insufficient control, or by selecting an SET that was deliberately voiced to conform to those "traditional" ideals. The Taboo wasn't and doesn't. It's as quick, articulate, transparent and apparently quiet in operation as the F2. So it's not a filter, however pleasant. The Taboo is about removing filters, haze and subjective distance. Like the F2, it's neither lean nor enhanced but harmonically simply satisfying. It's like clear mountain water but never bracing. It's more or less not there.


Into the Druids, bass performance is a very close second to the F2 which itself trails the F1. That is to say, the F1 is unnaturally well hung, the F2 still endowed and the Taboo far beyond average but not the beneficiary of current drive. The difference in this department telegraphs as completely unbroken, unshifted consistency of transient/sustain values and textures way down into the abyss with the transconductance amps. The valved champ becomes just a little less grippy in the depths, just a little plumper or looser. You wouldn't notice this during solo sessions - that's how well the Taboo does here. Only in direct comparisons do you learn that even more is possible.
Where the tables turn is in how images appear against empty space. Without incurring any loss of detail, visibility or introducing even subtle blurring or fraying of the edges, the Taboo's transitions -- between sound and silence -- are softer, smoother or less sudden. The F2 is sharper not in the sense of superior focus but in the sense of a protrusion or spike.


Like Photoshop's feathering command -- applied on overlays to create a very fine transitional gradation between the edges of imported cutouts and original background -- the Taboo simply refuses to get sharp in that sense, ever. It's not soft focus at all, something patently clear during A/Bs. There's zero loss of detail. It's simply a removal of the sharper quality exhibited by the transistor amp.
Another way of saying the same thing is referring to the
F2's pitch black silence as an abject absence of noise while the tube amp renders the silence less stark and more of a presence of space whereby the transitions appear more organic. This isn't a word play. It's a quantitatively very small difference but one that's nonetheless very apparent and far more an alteration of feel or gestalt than a difference in sound. The previous page called it spatial wetness. Those two words might seem very unlikely bedfellows but they do point squarely at this very phenomenon. It doesn't seem to operate in the realm of tone or THD as we usually think of with tubes - harmonic development, spectral density, bloom.


The Taboo clearly doesn't bloom. But neither does it default into becoming thin, lean or flat. There's a hint of sweetness but no warmth per se, at least not in the nearly parallel sense whereby warmth equates to minor darkness or timbral girth. Those aspects would be voicing. If the Taboo is voiced in any sense, it's to avoid being guilty of certain interpretative liberties rather than pulling specific tricks. Voicing by subtraction if you will.
In summary, the Zen Taboo is an exceedingly neutral, ultra-fast amplifier of exceptional transparency and in those respects, interchangeable with any number of really good transistor amps.


Where the pentodes come to the fore -- so far I haven't heard a transistor amp do these things -- is in the simultaneity of focus and softness and the added spatial drama in the soundstage that seems to be the special benefit of the Lucid Mode.


Yes, most S.E.T.s excel with soundstage holography yet few mate it to the nearly glacial purity of the Taboo. Because this Decware mini doesn't trip any of the usual 'tube excess' bells, you could say -- with a perfectly straight fact and true conviction in your voice -- that the Taboo is a tube amp which solid-state lovers would embrace in a heartbeat (well, except for the lack of V8 power which might require a leap of faith for subscribers to the power religion.)


A tube amp for solid-state mavens. That pegs the Decware Zen Taboo to a 'T' (and it goes without saying that we're talking about superior solid-state amps, not just any transistors.) My ongoing experiments with the FirstWatt amps and the Taboo drive home the point that the two camps have moved together closer than ever. The only differences that remain, at least in this particular juxtaposition, are bass (the transistors win) and space (the tubes win). Until I hear a solid-state amp that breaks down this last barrier, I will have to believe that this line remains drawn in the sand to compel music lovers to vote either/or in accordance with their priorities and preferences.


PS: Compare the lower edge of the Taboo's long left side above against the outline of the tube. That is the feathering command in action. It's engaged for the chassis edge, disabled for the tube. It's a subtle difference but if you envision it "active all over", applicable to every tone in the soundstage, you might have a good idea of what I've been trying to describe on this page.