An update on my experience with the First Watt SIT:
I had an opportunity over the weekend to hear a pair of SIT-1 mono amps in a system separate from the one in which I heard the SIT-2, but sharing some characteristics.
Both systems are in Rives-treated rooms and both are built around Zu speakers. The more completely Rives-treated room housed a system built around Zu Dominance loudspeakers. The other room had a system built around Zu Definition Mk 4 loudspeakers. I heard the SIT-2 in the Definitions system, and the SIT-1 in the Domance system. Both systems used digital sources, Meridian with Dominance and Berkeley with Definitions. I'll say that the DACs share essential traits of very clean presentation, quiet noise floor and tonal asceticism. The Meridian/Dominance system used a Pass preamp. The Berkeley/Definition system used a McIntosh C2300 preamp.
For context, let me say a few things about the speakers. Dominance is easily the finest speaker I've heard by any maker, under any circumstances in my entire audio life. It possesses the essential Zu qualities of crossoverless behavioral unity, frequency neutrality, tone density, convincing spatial dimensioning, revealing resolution, dynamic agility, scalar integrity, amp friendliness and easy drive -- all honed to an extreme level of aural competence. Dominance does more right in the presentation of music than any speaker I know of. It demolishes the pretense of the industry's most egregiously expensive efforts. That said, Definition 4 clearly inherited the essence of Dominance and sounds amazingly similar within its scalar limits, given Definition is about 1/4th the price. Where Dominance vaults beyond Definition 4 is in focus and precision of the spatial presentation (including the solidity of the aural holographic illusion), complete absence of cabinet talk, greater dynamic accommodation before congestion, even more authority and agility to the bottom end, generally even less coloration and I believe Dominance is a bit more efficient. Take everything good about Definition 4 and improve it linearly, then add new capabilities in focus, burstiness and (despite more drivers) behavioral unity. Let me put a finer point on it: Dominance is the first and only loudspeaker I've ever heard that impresses me as a lifetime purchase. Buy them; install them; you're done. So, did I hear the SIT-2 through better speakers and into a more corrected room? Yes. But the two systems had similar basic properties that were useful for rough and impressionistic evaluation of the two SIT amps.
Having heard both, I stand by my earlier expectation (and general rule) that when the same topology is implemented as stereo or mono amps, the monoblocks will be better, if you can afford the difference. In this case, SIT-1 monoblocks are $10,000/pr., against $5,000 for the stereo amp. In this case, the Dominance system is in a somewhat over-damped room, whereas the Definitions system is in a room that has a lighter Rives treatment, eats bass, but is still on the lively side elsewhere. With only 10w per channel available from either SIT amp, the dual power supplies give the SIT-1 perceptibly more dynamic ease, especially when crescendo dynamics hit both channels at once. For me, this is valuable, especially with low-power amplifiers. But this is the minor improvement of SIT-1 over SIT-2.
Where SIT-2 left me disappointed by the way it tamps down the finish of a note compared to a well-designed SET amp, SIT-1 has a variable that lets you get closer to genuine SET musicality. The SIT-1 manual bias control introduces a measure of tunability to the amp's musicality that drives differences more than subtle and less than stark. The basic traits of the SIT prevail: clean, absence of grain and grit, very good tone for solid state, deep and agile bass, effective aural neutrality. But you can favor 2nd order harmonics, roundness and warmth, or push the sound in the direction of pentode-like definition with the speed of simple circuits....or anything in between. The perception of tube-like note decay is variable too, and while getting the "whole note" isn't as complete an experience as with a well-implemented SET circuit, you can get appreciably closer than with SIT-2 and its static configuration. Ironically, the owner of the amps and I preferred mildly-different settings, but both were within the same realm of essential rightness. He owns solid state but preferred his bias controls set for warmth and 2nd order harmonic profile; I own fast and transparent SET but preferred the bias controls set for more elevated definition while keeping good tone. Within its dynamic limits, the SIT-1, in a stereo pair, is the best communicator of music through solid state amplification I've heard, and you get some latitude for how much you want it to emulate a clean and ascetic Pass SS amp, for example, or towards the amber tint of the most romantic triodes. SIT-1 is never going to sound less than highly credible, however you voice it. But you are voicing it regardless where you prefer the bias control be set. It wold further benefit in this system, from a more expressive preamp.
I wouldn't give up my Audion SET amps for a pair of SIT-1s. But for someone (like the owner) who is acutely bothered by the slightly higher noise floor of SET or has other reasons to eschew vacuum tube amplification of any topology yet appreciates tube sound for its convincing musicality, SIT-1 allows you to get closer than does SIT-2, and by a margin that I consider significant enough to say that I hear SIT-1 as being a higher value point at $10,000 than SIT-2 is at $5,000. Put another way, I would not own SIT-2, but if I didn't already have excellent SET amps, SIT-1 would be satisfying. I can only say that about the McIntosh MC1.2kw (specifically), the Larvardin, and now this SIT-1 -- and it's the SIT-1 that sounds tonally most authentic among these. Its major weakness is its power limit. Neither SIT amp delivers the sense of headroom and grace near clipping that a good tube amp does. I'd love to hear a parallel single-ended SIT amp.
I still want to hear SIT-1s driven by a DHT preamp, to hear whether Srajan's postulate about the leap in results is true for me. But this was one step further in gaining experience with these amps.
One more thing: the Dominance system I listened to also had a QOL processor connected. I switched it out (bypass) for all of my evaluations of the amplifiers and speakers but did some comparative listening, QOL engaged and disengaged. Spatially, the QOL is entertaining. In that respect it seemed like a vastly-refined implementation of the early SRS outboard processors. It expanded the soundstage width only marginally, but it tended to expand the spaces between instruments/performers within the soundstage, and anything away from the center was pushed further away from the center and toward the soundstage perimeter. The presentation of holographic depth was enhanced but not always realistically. The spatial effects would be thoroughly entertaining with movies. It was expansively entertaining with music but not in a way that impressed me as more realistic. With the QOL switched in, I thought the sound became tonally less authentic though dynamically more exciting. Any voice sounded tonally more human with QOL out than in. Leading trainsients of notes and percussive events are definitely enhanced in positive ways. The dynamic clarity and transient precision are improved but the downside is that the balance of attack v. decay is altered from what sounds most authentic, at least to me. In nearly three hours of listening, there wasn't any music that the QOL made sound more authentic to me, but it was consistently able to make any disc sound more exciting, whether the "excitement" was in the original recording or not. I do agree it seems to recover some definitional information that sounds like it's not artificially derived. If that quality could be better isolated from the less natural spatial warps and disturbances to the attack/decay balance, it might prove aurally valuable. But not yet, for me. It has the trait, upon immediate swithover from engaged to disengaged, to make make either one sound incorrect for a lingering moment. But lingering always led me back to having QOL out of the circuit. Others may have a different preference. Hearing the QOL makes it obvious why it's controversial.
Phil
I had an opportunity over the weekend to hear a pair of SIT-1 mono amps in a system separate from the one in which I heard the SIT-2, but sharing some characteristics.
Both systems are in Rives-treated rooms and both are built around Zu speakers. The more completely Rives-treated room housed a system built around Zu Dominance loudspeakers. The other room had a system built around Zu Definition Mk 4 loudspeakers. I heard the SIT-2 in the Definitions system, and the SIT-1 in the Domance system. Both systems used digital sources, Meridian with Dominance and Berkeley with Definitions. I'll say that the DACs share essential traits of very clean presentation, quiet noise floor and tonal asceticism. The Meridian/Dominance system used a Pass preamp. The Berkeley/Definition system used a McIntosh C2300 preamp.
For context, let me say a few things about the speakers. Dominance is easily the finest speaker I've heard by any maker, under any circumstances in my entire audio life. It possesses the essential Zu qualities of crossoverless behavioral unity, frequency neutrality, tone density, convincing spatial dimensioning, revealing resolution, dynamic agility, scalar integrity, amp friendliness and easy drive -- all honed to an extreme level of aural competence. Dominance does more right in the presentation of music than any speaker I know of. It demolishes the pretense of the industry's most egregiously expensive efforts. That said, Definition 4 clearly inherited the essence of Dominance and sounds amazingly similar within its scalar limits, given Definition is about 1/4th the price. Where Dominance vaults beyond Definition 4 is in focus and precision of the spatial presentation (including the solidity of the aural holographic illusion), complete absence of cabinet talk, greater dynamic accommodation before congestion, even more authority and agility to the bottom end, generally even less coloration and I believe Dominance is a bit more efficient. Take everything good about Definition 4 and improve it linearly, then add new capabilities in focus, burstiness and (despite more drivers) behavioral unity. Let me put a finer point on it: Dominance is the first and only loudspeaker I've ever heard that impresses me as a lifetime purchase. Buy them; install them; you're done. So, did I hear the SIT-2 through better speakers and into a more corrected room? Yes. But the two systems had similar basic properties that were useful for rough and impressionistic evaluation of the two SIT amps.
Having heard both, I stand by my earlier expectation (and general rule) that when the same topology is implemented as stereo or mono amps, the monoblocks will be better, if you can afford the difference. In this case, SIT-1 monoblocks are $10,000/pr., against $5,000 for the stereo amp. In this case, the Dominance system is in a somewhat over-damped room, whereas the Definitions system is in a room that has a lighter Rives treatment, eats bass, but is still on the lively side elsewhere. With only 10w per channel available from either SIT amp, the dual power supplies give the SIT-1 perceptibly more dynamic ease, especially when crescendo dynamics hit both channels at once. For me, this is valuable, especially with low-power amplifiers. But this is the minor improvement of SIT-1 over SIT-2.
Where SIT-2 left me disappointed by the way it tamps down the finish of a note compared to a well-designed SET amp, SIT-1 has a variable that lets you get closer to genuine SET musicality. The SIT-1 manual bias control introduces a measure of tunability to the amp's musicality that drives differences more than subtle and less than stark. The basic traits of the SIT prevail: clean, absence of grain and grit, very good tone for solid state, deep and agile bass, effective aural neutrality. But you can favor 2nd order harmonics, roundness and warmth, or push the sound in the direction of pentode-like definition with the speed of simple circuits....or anything in between. The perception of tube-like note decay is variable too, and while getting the "whole note" isn't as complete an experience as with a well-implemented SET circuit, you can get appreciably closer than with SIT-2 and its static configuration. Ironically, the owner of the amps and I preferred mildly-different settings, but both were within the same realm of essential rightness. He owns solid state but preferred his bias controls set for warmth and 2nd order harmonic profile; I own fast and transparent SET but preferred the bias controls set for more elevated definition while keeping good tone. Within its dynamic limits, the SIT-1, in a stereo pair, is the best communicator of music through solid state amplification I've heard, and you get some latitude for how much you want it to emulate a clean and ascetic Pass SS amp, for example, or towards the amber tint of the most romantic triodes. SIT-1 is never going to sound less than highly credible, however you voice it. But you are voicing it regardless where you prefer the bias control be set. It wold further benefit in this system, from a more expressive preamp.
I wouldn't give up my Audion SET amps for a pair of SIT-1s. But for someone (like the owner) who is acutely bothered by the slightly higher noise floor of SET or has other reasons to eschew vacuum tube amplification of any topology yet appreciates tube sound for its convincing musicality, SIT-1 allows you to get closer than does SIT-2, and by a margin that I consider significant enough to say that I hear SIT-1 as being a higher value point at $10,000 than SIT-2 is at $5,000. Put another way, I would not own SIT-2, but if I didn't already have excellent SET amps, SIT-1 would be satisfying. I can only say that about the McIntosh MC1.2kw (specifically), the Larvardin, and now this SIT-1 -- and it's the SIT-1 that sounds tonally most authentic among these. Its major weakness is its power limit. Neither SIT amp delivers the sense of headroom and grace near clipping that a good tube amp does. I'd love to hear a parallel single-ended SIT amp.
I still want to hear SIT-1s driven by a DHT preamp, to hear whether Srajan's postulate about the leap in results is true for me. But this was one step further in gaining experience with these amps.
One more thing: the Dominance system I listened to also had a QOL processor connected. I switched it out (bypass) for all of my evaluations of the amplifiers and speakers but did some comparative listening, QOL engaged and disengaged. Spatially, the QOL is entertaining. In that respect it seemed like a vastly-refined implementation of the early SRS outboard processors. It expanded the soundstage width only marginally, but it tended to expand the spaces between instruments/performers within the soundstage, and anything away from the center was pushed further away from the center and toward the soundstage perimeter. The presentation of holographic depth was enhanced but not always realistically. The spatial effects would be thoroughly entertaining with movies. It was expansively entertaining with music but not in a way that impressed me as more realistic. With the QOL switched in, I thought the sound became tonally less authentic though dynamically more exciting. Any voice sounded tonally more human with QOL out than in. Leading trainsients of notes and percussive events are definitely enhanced in positive ways. The dynamic clarity and transient precision are improved but the downside is that the balance of attack v. decay is altered from what sounds most authentic, at least to me. In nearly three hours of listening, there wasn't any music that the QOL made sound more authentic to me, but it was consistently able to make any disc sound more exciting, whether the "excitement" was in the original recording or not. I do agree it seems to recover some definitional information that sounds like it's not artificially derived. If that quality could be better isolated from the less natural spatial warps and disturbances to the attack/decay balance, it might prove aurally valuable. But not yet, for me. It has the trait, upon immediate swithover from engaged to disengaged, to make make either one sound incorrect for a lingering moment. But lingering always led me back to having QOL out of the circuit. Others may have a different preference. Hearing the QOL makes it obvious why it's controversial.
Phil