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Test #1: F1, F2 and Decware Zen Taboo on 12-ohm 101dB Zu Cable Druids:
The F1 and F2 have an unfair advantage. When applied as intended -- i.e. with the right speakers -- even very good valve amps find themselves on the short end of one particular stick. That unfair advantage is called control (or cone acceleration if you want to get fancy.) It's something devotees of unconditionally stable load-invariant muscle amps have known all along. These transconductance amps achieve the same kind of über control with minimalist circuits and a bare minimum of output devices. It's rock-hard muscle without the beef cake physique but sting-like-bee speed. This control translates as articulation and crispness even at low levels and with albums where the lead vocalist is miked such as to be somewhat recessed and overpowered by the band. Without moving such singers forward or "making them louder", the upped definition and sculpting of each note makes it appear as though the singer was louder just because it's easier to distinguish him or her from the surroundings. It's a bit like the difference between an actively driven speaker and the same speaker with a passive crossover.


You could call this effect greater crispness, precision or an elimination of subliminal indecision. You could also say sharpness which, depending on your bias, might carry a somewhat negative connotation. Comparing the F2 to a superior valved SEP like the 6wpc Decware Taboo, it becomes tricky business to fish for appropriate descriptors and capture the remaining differences honestly. Remaining differences? Are things that close? You bet. Let's start with where they completely overlap - transparency, thereness and microdynamic jump factor, all side effects of removing filters between you and the ghosts we call performers in a virtual soundstage.


There's a small amount of sweetness on especially bowed and massed strings which is sometimes believed to be the sole providence of tubes. The F2 does that too. Where the F2 goes farther is in the bass (though the F1 reigns supreme here). It seems to be a function of bass transients being even faster or more unfettered than with the SV83BEs I'm listening to in the Zen Taboo. Or it could be a function of the F2's higher output impedance which, in this instance of an extremely self-damped main driver in the Druids, would be a good thing. Likely, the main hero responsible is current drive which nearly makes the Zu Method subwoofer optional. The Decware amp is counter-intuitively good in the bass and into these speakers - but both F1 and F2 are even more defined, articulated and developed (the F1 the mostest).
Neither the Taboo nor the F2 are bloomy amps per se but they both have more apparent harmonic texture -- a hard-to- describe sheen of roundness -- than the F1 which comes across as leaner and spikier. The flip side is that when things get raunchy and convoluted, the F1's special attributes come to the fore as though it had the greatest separation power. On material that's easier to breathe through, the F2 and Taboo appear slightly more relaxed or gentle while the F1 maintains a subliminal on-alert readiness or tension. Neither Taboo nor F2 are fat by any stretch of the imagination but compared to the F1, they're slightly plumper.
None of these three amps are in the least bit guilty of that
chalkiness in the treble which, outside of spatial flatness or "partial dimensional muting", is the quality that detracts me the most from enjoying the average transistor amp. Those get whitish in the high frequencies and slightly flat in the midrange. However, once we talk soundstaging or texture, the Taboo has the unfair advantage - thermionic output devices. Without at all undermining transparency by reinserting some type of pleasant filter, its clarity is completely devoid of any sharpness whatsoever. The F1 can get a bit pungent at times and even the F2 still retains just a bit by comparison. It would be convenient to accuse the valves of undue softening. However, softening simultaneously suggests a decrease of magnification power on tiny details, a kind of blurring or fraying around the edges. That's patently not the case with the Taboo (the valved Zen amp vs. the solid-state Zen amp).


What causes this difference? It could be a slightly shifted weighting of leading edges though the F2 does not at all sound as though it were - er, leading by them transients as sand amps can. Whatever exactly is it that makes the Decware Taboo sound slightly mellower - or mellifluous yet accurate, to use a word Jonathan Scull was fond of? I don't know because it doesn't sacrifice any detail or transparency. A word that suggested itself during a listening session with the F2 was definitive. Every tone in the soundstage was very definitive or deliberate. With the Taboo, something about how sounds appeared in the empty space was wetter and somewhat more buoyant. Curiously, this seems to have little to do with harmonics (at least how we usually think about those in terms of producing body, texture and glow.)
If you didn't know it going in, you would never call the F2 a sand amp. All the popular 'telltale' signs are absent - well, except for the extraordinary grip in the bass that cleanly separates the leading edge attack from the subsequent bloom of resonant cavities. If you compared it to the Taboo behind your black curtain in an A/B/A/B sequence? Then you might suspect something even though quantitatively speaking, it's a very small difference. Both amps walk on that edge that separates lean from voluptuous. Both are subjectively fast yet never skinny or tonally bleached. The F1 in this lineup strikes me as somewhat lean and harmonically reserved.
Personally, I side with the F2 - but not remotely by the margin I anticipated due to the headspace the accompanying design descriptions created. While I prefer
the F2 coming as I do from tubes by a small lead, I fully appreciate the F1's particular strengths. I can readily see how someone else would prefer it. It's very much like seeing a different set of assets without spotting any liabilities. Something in how you're wired pulls you to one. Still, you remain keenly aware that the other is just as attractive. It's simply different, not inferior or flawed.


Put differently, the closer to the center you get -- the mythical neutral, whatever that's supposed to be -- the smaller the differences become. That doesn't mean you can't clearly perceive them. You do - at least in this instance, in how the two transistor amps have a different distribution of harmonics and the tubes telegraph specific virtues in one particular area. But plainly, these differences no longer are gross characterizations or artistic liberties. They're subtle flavors that don't so much sound different as they rotate the overall gestalt. The musical matter is plainly the same objects. Perhaps the lighting on them is somewhat adjusted. I don't believe any of these amps are voiced in the sense that a designer's personality superimposes itself on the music in any recognizable ways. They're all within spitting distance of the center and simply approach it from slightly different directions. In fact, they seem to deliberately not be voiced. Whatever differences remain are intrinsic to the output devices and circuits - or as Nelson put it, "the harmonics I get aren't designed in but the result of the parts, the bias applied to them etc...".
Now that I have an initial fix through my regular speakers on how the F2 differs from the F1, the next experiments will involve the Medallion III and "Hornette". For today, let's recap what I think thus far. It boils down to a mind twister of sorts. The F2 isn't exactly identical to the kind of tube amp represented by Steve Deckert's affordable low-power creation which majors on speed and definition and then does some special spatial trickery I'm still trying to get a firm handle on. But the F2 is closer than perhaps any other transistor amp I've had through here yet. It does certain things better like bass delineation into the abyss whereby nothing recedes subtly into the background but stays solidly put and intelligible. It is arguably fully the equal in that realm variously circled by terms like thereness, immediacy or directness. Where it's subtly different -- though not inferior -- is how the musical images appear against the backdrop of space.
The difference between sound and no-sound is crisper or
starker with the F2. With the Taboo, space or no-sound seems less black to make the difference -um, not less dramatic but less sudden. It's hard to describe but easy to hear. It's the one area where the word organic presents itself. Visually, I think of this as the feathering command in Photoshop. If you cut out an object to superimpose it on a different background, the feather command incurs a very faint transition (a tiny area of overlap so to speak) to avoid making edges too defined or separate from the background. The F2 heightens the difference between space and object, the Taboo plays it down somewhat. Curiously, this doesn't diffuse drama as though something got diluted. It's very dramatic in its own right.


It's the one area where I personally prefer the tubes. It's something I hear with nearly all superior SETs (or SEPs as it were - my Audiopax Model 88s weren't triode either). Most of them simply don't exhibit the near glacial directness of the Decware amp by being just a mite softer, a quarter click down from total dead-on focus. If your idea of tube sound revolves around warmth, bloom and comfort, neither the Taboo nor the F2 will even apply. Conversely, if transparency, speed, timing and dynamics are your poison, both are smack inside the winner's circle. There they walk hand in hand as it were, each making its own footsteps. When you look back, their tracks run in parallel and are separated by precious little.


If I could graft my ideal amp from the stock the three present contenders provide me with, I'd use the F2 as my root. I'd slip in the bass gene of the F1 and the OST strand of the Taboo [organic space thang] and -- wishful thinking alert -- I'd turn the F2 into a voltage-source amp so it'd drive regular speakers as well and throw in the particular Audiopax molecule that adds adjustable THD to tweak the final flavor depending on what speakers you want to use. Back in the real world, however, I'd vacillate between the F2 and Zen Taboo depending on mood and whether Saturn was retrograde or not. Nelson has promised a review sample of the Aleph J when it becomes available, a voltage-source amp for conventional speakers. I wonder how much transconductance drive it'll exhibit, how its harmonics will flavor the soup and how it'll compare to the Decware mini. For now, the F2 is a hybrid of sorts. It straddles valves and transistors by being just slightly sweet (but not warm); harmonically satisfying without feeling enhanced; a PRaT champ (but not quite as driven as the F1); and great fun to listen to at especially low volumes where its superior clarity doesn't activate the twitch for the remote. The next installment will investigate the Medallion III speakers on the same three amps.