This review page is supported in part by the sponsor whose ad is displayed above
Already into early listening sessions, the F4 had me work my phrase maker to clearly define its most obvious flavor: relaxed ultra resolution. Like a seed mantra, those three words are potent. There's the inherent polarity of what's often mutually exclusive. 'Relaxed' is a state of being. In the context of fine audio, 'resolution' as such is recognized by mental faculties. It involves a kind of activity, an alertness to stay put or else the notion of resolution evaporates. 'Hyper resolution' is its extreme expression. The act of listening has become tense, unnatural and exhausting. 'Ultra' is similarly heightened but lacks the negative spin. Now make the two polarities meet in the middle: a relaxed open state of non-mental being that's free of concerns. It's thus free also to effortlessly perceive a tremendous amount of very fine aural detail if that's what happens to present itself. But this doesn't trigger any active collection from us. It simply is.

Just how much the F4 already resolved being fronted by Raysonic's mid-priced CD168 and matching 20dB-gain C200 preamp, DeVore Fidelity's revealing Nines at chain's end, I first appreciated during a customary abdominal workout on the listening room floor (multi-tasking in today's cell phone society). My wife was meditating next door so the volume had to hover a mere few clicks above inaudible. Finding myself supine on a camping mat for my neo Pilates floor routine, my normally upright audio perspective had turned diaper rug-rat. Yet, to borrow from a well-loved phrase, I could hear the carpet fibers grow. The amount of audibles in a superior recording [Tiny Island on Opus 3, trusted stand-by for late-night background sessions] was spectacular by how it didn't trigger the volume reflex. I delighted instead in following the wispiest smoke signals of sonic storytelling while creating heat in the belly. And I mean very subdued volumes which you'd otherwise find terribly subdued.

In tech talk, the noise floor of the F4 is absentee, period. But there's more. Line-level tubes can be ferociously dynamic little things. Because the F4 does become an operational entity with the preceding preamp (or source) more than customary, those low-level valve dynamics seem to couple more directly. They show up on the speakers at levels that would normally turn you off, literally, by shutting down the system. It's as though you played pass the buck with a complex message. By the time it gets to the last person in line, the meaning has changed. The F4 sounds as though it has cut out the middlemen. Here's the kicker. Direct connection between source and amp has gotten a bum rap. Astute listeners have noticed how superior active preamps invariably add body, dynamics and dimensionality. The F4 driven by such a superior preamp is a new kind of direct drive. It raises resolution by removing redundant stages -- more directness -- but does so by incorporating preamp action undiluted. So the amp remains transparent to the preamp. And pre-amplification is one step closer to the source and thus presumably purer than the growing of high-level gain.

Purity indeed is the next core term. It's not a separate quality though. It's part of relaxed ultra resolution. By being more an extension of the preamp than a separate entity with its own voice -- the preamp becomes the voltage gain stage of the amp -- the final sound from the above setup had valve-powered tone, micro dynamics and dimensionality. It also had excellent beyond-tubes bass and the superior resolving power of a stupendously low noise floor rarely achieved with conventional preamp/amp pairings (all of the F amps have been deathly quiet but none of them could exactly be called conventional). None of the F amps is far removed from the others either. They rather seem like fine variations on a sonic core theme while they diverge in applications to become quite specialized - crossover-less speakers for the first two transconductance amps for example.

With the F1 and F3 in-house and having heard the F2, the F4 takes from the F3 its subtle sweetness and seemingly removes yet another layer of innate tension. This is an important but easily misunderstood point. Going a bit native in Cyprus means that Arab Pop shows up on the for-fun menu -- say Kadim Al Saheer, Amr Diab, Nancy Ajram, Elissa -- to sample the local fare while living here. While their vocal craft is highly enjoyable, their albums often suffer relentlessness from overproduction, compression limiters and such to sound loud, driven and ultimately exhausting. The point is, the above-mentioned qualities work on such decidedly non-audiophile fare just the same.

The F1 treats it more angular and edgy, conveying first and foremost the sensation of drive and transients. The F4 -- or really, this particular Raysonic preamp working through the F4 -- relaxes it and makes these albums pleasing to finally enjoy their glorious voices. Potential misunderstanding arises from an assumption: that of profound editorializing when inserting a new amplifier alters musical gestalt in such obvious ways. In this case, relaxation could suggest a lack of drive, a somewhat listless shuffling along rather than a purposeful gait that propels the music onward. Something is taken away or let go. This changes how the listener reacts. Isn't that editorializing? Shouldn't an overproduced Pop album sound as such, i.e. relentlessly bad?

For a superior album whose music is plainly driven, let's turn to Cal, the second outing of Son de la Frontera [Harmonia Mundi/World Village 468069], a formation that introduces the Cuban tres alongside Flamenco guitar to the Spanish folk music idiom for a very earthy, dirty and exciting sound which Jackson Browne purportedly called the best he'd heard in any style of music in a long time. Sure enough, the C200/F4 combo treated this album the same - some of the innate propulsion of the foot stomps, hand claps, rapidly strumming guitar and tres and hoarse voices had relaxed. The presentation was wide open, exceptionally refined, detailed and dynamic - yet with less grip and urgency than normal. It would take a lot of preamp swapping -- ModWright SWL 9.0SE and LS-36.5, Wyetech Jade, Supratek 101D/6H30 Cabernet Dual, Bel Canto PRe3, Coda X0.5 -- to learn how this very tacit quality traveled intact (to point at the amplifier) or changed from combo to combo (pointing at the preamp).

Conceptually, it seemed very sensible to assume that the role of the preamp, with this amplifier, becomes more important than normal not just in how it impacts the sound but also the gestalt. With three digital sources in the crib that allow for direct-drive -- Raysonic CD-168, Ancient Audio Lektor Prime, Weiss Engineering Jason + Medea combo -- I also meant to shift the burden solely on the source and see what happened. Clearly, the F4 is quite the mother of unusual lessons and the most flexible of all FirstWatt entries thus far. It's quite possibly also the best sounding of this wild bunch. If the preamp parade was to net the expected outcome -- more than usual shifts in presentation -- the commentary would end up being far more about specific preamp/amp combinations than the amp per se. Which also means that if you favored valves, you could now transfer their specific qualities from the low-level domain through a transistor amp more unadulterated than before without having to bother with the wear and potential failures of power tubes. That's an interesting real-world promise and wallet wise, more sensible than strapping an outboard power buffer to a micro-power SET.

Some hard figures for stereo use. With Coda's X0.5 transistor preamp set to 18dB max circuit gain and the master attenuator fully open, audiophile recordings of low median levels gave me just the right playback level on the 91dB DeVores, sitting 12 feet from the speakers and energizing a total air volume of about 32' x 28' x 11' which includes the open adjacent spaces. Increasing source output voltage from 2V to 5V got quite too loud on such recordings. On average recordings, I attenuated the Coda by about 5dB. With the 12dB ModWright preamp, I could run just a bit short on gain when the album wasn't recorded Pop-level hot.

From this follows that your preamp will be running in the top ¼ of its volume range. That might seem dangerous but isn't in the least. Instead of throwing it away, you're simply using the voltage gain it produces (in fact always and regardless of volume if its attenuator sits ahead of the gain stage to simply trim the input signal from your source). To really drive the point home against global warming and excessive energy consumption, take the above scenario and replace the F4 with my 50-watt Audio Sector Patek SE. It'll mean dumping 30dB of gain. That's what the Pateks produce every running minute. That's what you'd have to attenuate at the preamp to not go deaf. This isn't a fringe case. 26dB is a perfectly normal figure for amplifier gain. With speakers like the DeVores and preamps of 20dB gain, nearly all that amplifier gain becomes superfluous and wasteful. Hello?

While running things close to wide open, often with just 5 or 6dB of attenuation or occasionally none, I reckoned that one could potentially clip the preamp. Off went an e-mail to the maestro: "I've heard digital clipping before and it's pretty nasty. I know what tube amps sound like when clipped. I've never yet managed to clip any transistor amps on the speakers I listen to. It occurred to me that with a standard 2V source and the F4 in stereo mode, on speakers below necessary sensitivity, some crazy listener could potentially get his preamp to clip. Ha, the theoretical musings of non-engineers. It's possible though, isn't it? Any idea what that would sound like - one preamp clipping?"

"It's absolutely possible although I have not experienced it. When I went through the Stereophile reviews test results, I came up with a list of how many preamps were capable of driving the F4s based on gain and voltage swing. I concluded that about 2/3 of the candidates have enough gain and swing to potentially clip a single F4 first, or at least come close to it. A lesser proportion can get the 100-watts with balanced mode, including our own X1 which exceeds the amp by about 5 volts or so, balanced pairs or single-ended. I expect that a tube preamp will clip a bit more like a tube, and a solid state preamp to clip in what we recognize as the hard SS clip. It's a very interesting twist that you have come up with that I did not previously appreciate - the notion of such an amp allowing greater appreciation of the preamp. Cheers for that."

To equalize preamp gain differentials, I drafted the 101dB Zu Definition Pros into service next, giving more than sufficient output even over the least powerful preamp. Source of choice in this context became the Swiss Weiss Engineering Jason + Medea duo leashed up in its twin XLR scheme set to 176.4kHz and 24-bit word length. Its solid-state class A ultra-low Z output stage seemed to have the most drive of my source options, translating as both accuracy and a sense of pressure regardless of level and preamp.

The long and short of my walk down preamp strada? The sense of innate relaxation is intrinsic to the F4. It's the Antichrist of electronic artifice, grain, brittleness - the whole bag of overt and subliminal reminders that machines are making your music. Whether this relaxation turns a bit limpid or the equivalent of a martial artist completely at ease because he's unafraid depends on the preamp. The two ModWright preamps exhibited more of the limpid flavor, the Raysonic the athletic kind of relaxation. Whether the Ray's higher gain was responsible I couldn't determine of course. Playing a shockingly dynamic track like the buleria "Chisera" which opens Juan Carmona's Sinfonia Flamenca [Le Chant du Monde/Harmonia Mundi 2741411] with its Indian-style vocal percussion, solo guitar, symphonic forces and gitano vocals only scores fully if your hackles are up and your spine a'tingling.

The ModWrights weren't quite as muscular, raw and kicking as the Raysonic. That also exhibited more image density in this context. The Wyetech Jade was very similar to the Coda X0.5 - ultra-quiet and 'fast' but tonally not quite as interesting. But shy of these minor shifts between preamps I'd all call modern and close to neutrality, the sonic landscape remained fixed. "Chisera" had loaded dynamics yet none of the pushiness that some listeners equate with highly dynamic presentations (often through horns). Again, low-level resolution was stupendous. In fact, it showed off a minor failing of my Zus which, with their customary tube power, hadn't been noted earlier - occasional grain or grit from the horn tweeter. This was dependant on recording but absentee over the DeVores, thus not due to soft- but hardware. This is subtle stuff becoming relevant only when magnifying power grows intense. The F4's appeal lies squarely in pulling this off without ever changing over into the hyper field where details become annoying. In short, first impressions firmed up into a solid assessment. Relaxed ultra resolution and purity are indeed what this amp is about. Even with the transistor Coda preamp, it didn't turn bluish cool and boring, traits I find are quite common with class D amps that can be all rez but little tone.

Compared to a thoroughly modern direct-heated triode amp like Yamamoto's A-08S, the F4 has less texture, more extended treble, better bass, more dynamic macro swing, similar timbres and more resolution. The Yamamoto has more stuff hanging between the sounds, the F4 is cleaner. Tubes are sometimes accorded 'artificial intelligence' because their non-linear behavior can strangely highlight a performer out of her surroundings to sound sexy, slightly polarized like sunglass contrast. Of course the 'intelligence' credit after 'artificial' is there only because we fancy such effects. There's nothing intelligent about 'em. A recording engineer knowing what he put to disc might call them dumb and arbitrary. The F4 doesn't do whatever that is. Compared to a high-power push-pull valve amp like Raysonic's 8 x 5881 monos, the F4 is less juicy and pressurized from within but cleaner and more finely articulated, perhaps less dynamic on the macro scale but more distinguished on the micro. Bass is less voluptuous but tauter and springier. In short, the F4 does not sound like tubes. Yet especially lovers of micro-power triodes done up linear, not sloppy, will hear a lot of common ground; plus more extra goodies than diminishments to possibly come out ahead depending on how individual aspects get weighted. Finally, S/N with the Passie goes places tubes never will.

Reserving my Supratek Cabernet Dual for last, I decided to start the mano-i-mono exploration backwards - with speakers plainly not in need, i.e. this very 101dB setup. What would quadrupling current gain accomplish? Presumably playback levels wouldn't go up since F4 mono strapping still makes no voltage gain. To not mess too much with cables during swaps from one amp to two*, I did the conversion by bridging pins 2 and 3 on the XLR inputs with the U inserts. With the second amp powered up whether connected or not, I now merely moved over one speaker cable connection, did the same for one RCA interconnect, inserted the pins and the cable jumper from + to + speaker terminal. Presto, 25 watts upgraded to 100 watts paralleled "for more current and less distortion". Back in the seat, CD remoted out of 'pause', the results were - what?
*You can accomplish the same by doing a reverse biwire, 4 leads on the amp, two on the speaker.