SET amp comparable to First Watt SIT 1?

If you want the clarity, quietness, speed of the SIT-1 with superior tonality and spatial presentation in SET, an Audion amp is perfect, and I have to say best.

In your price range you can choose from a simple 300B stereo power amp at $5.5K, up through $18K and any choice would best the SIT-1, by varying degrees. Since you are interested in 300B and alternatives, the DUO is interesting for you at $6K as it can run 2a3, 45 and 300B at your discretion. But you can trust you'll get excellent sound from a 300B, so given your price range, stepping up to the Golden Night monoblocks at $10K/pair is the sweet spot. 10w each amp, all silver wiring, wide-band OPTs. These amps ship with JJ 300B tubes. Put them aside as spares and spring for a pair of KR 300B balloon glass. That will give you high integrity in the bass region where so many 300B amps fail. Midrange tonality, dimensioning and detail are beyond reproach. Top end is extended, spacious, harmonically legitimate and top-to-bottom speed and dynamics are consistent (and *fast*).

There are PSET alternatives, PX25 variants in the line, and 845 monoblocks. If you want plenty of dynamic headroom, the $14K/pr. Black Shadow II 845 SET monoblocks and the $18K/pr Golden Dream 300B PSET monoblocks each output 24 watts. The 845 has a ton of shove but you don't absolutely need it with the Voltis. The 300B PSET Golden Dreams have more power than you need but that amp is musically gorgeous, harmonically complete and full of realistic nuance, so the circuit is worth the overkill.

Phil

We don't have enough info from the OP wrt room size/characteristics and which model Volti he's considering, to answer definitively. Also, I can't find an impedance spec on the Volti site. Nevertheless, I have owned OTL amps and like many of their characteristics, but I've never heard one, especially using massed output tubes, that has the sheer transparency, speed, holistic tone and spatial precision of Audion SET overall, and especially the Golden Dream monoblocks, which would only require a little stretching of the OP's stated budget. I think at ~100db efficiency, 24w with smooth clipping should be plenty, unless the room is cavernous.

I also think at a step-down price of $10K/pair, the Audion Golden Night @10w has most of the qualitative character of the Golden Dream, minus some of the shove. With KR tubes, the bass will gain some discipline. Having recently gotten some experience with the Takatsuki 300B, which is very good, I'll still take the KR balloon glass full range, and it's half the price. Equally well made.

Charles, you know I use Zu speakers at 101db/w/m, and that I've written elsewhere that while such a speaker can clearly be paired with some of the beautiful low-watt 2a3 and 45 offerings, I think they give up too much shove and dynamic fidelity. When 300B is done as well as Audion implements it, and there's a PSET option, why cramp yourself? For shove over ultimate nuance and transparency, the 845 Black Shadow is squarely in the OP's stated economics too, and would put a firmer grip on the very bottom end. But overall, for what the OP seems to be after, he can pretty much index his preferred price to the Audion SET offerings and go, knowing that for the dollar level chosen the march to the Volti will be sublime.

Phil

tmare,

PSET (Parallel Single-Ended Triode) topology with 300B tubes will do fine at the Volti- efficiency level, your listening habits and your room size. On nominal 100db/w/m speakers using for example 24w Audion PSET 300B Golden Dreams, at 1m you'll yield 112db at the 16th watt, and be quite usable into soft clipping by 115db. Now, you'll be sitting 3m away, and room surfaces, contents, etc. will reduce those actual and apparent levels at your listening position. If you routinely listened to full orchestral music at symphony hall crescendo live levels, you'd probably want a little more dynamic headroom in that listening space. But what you outlined indicates PSET 300B will be more than sufficient on a ~100db/w/m speaker.

You can drive keep most aspects of the 300B SET sound with a push-pull configuration. You'll gain some bass discipline but lose some nuance and tonal purity. Still good. But unless you find a four-tubes/ch p-p amp, the actual dynamic gain over PSET will be only about 3db.

A ~24w 845 SET amp will have the same measurable dynamics but will sound subjectively as having more "shove." For your stated preferences, I don't think the trade-off of 845 SET muscle for 300B PSET nuance and transparency is necessary.

For reference, on one of my systems, I use 24w on 101db/w/m speakers in a 21x14x 8.5 room, unbounded in two walls so he acoustic pressure dissipates into an open plan house. Seating position is 11.5' from the centerpoint between speakers.  I can cave my skull in with full on rock or symphonic music. You'll do fine.

I suggest against 211 amps. Tube choices are narrower, and you don't get the 845's shove nor the 300Bs nuance, tone and delicacy.

Phil

Charles,

The XLS variant of the 300B can be used in a straight 300B circuit, with normal 300B power output. Used in an amp configured to leverage the XLS tube's higher power potential, it takes on slightly different character but sounds impressive nevertheless. ~18w of premium 300B sound is nice. I'm right now able to compare Takatsuki, the EML 300B XLS and the KR 300B balloon in both Audion Golden Dream and the Luxman Anniversary MQ300 SET amp. The three tubes have roughly the same influences on both amps, but each amp imposes its signature on all three tubes as well. For me, the KR 300B prevails as the most objective and the most dynamic of the three tubes. The Takatsuki is very nice and is the most euphonic of the three but without bloat. The EML is the noisiest and the least consistent in octave-to-octave consistency, but these are not vast differences. Actionable but not vast.

I abandoned the EML tubes for chronic noise and reliability troubles. Perhaps you got better samples than me. The KRs take a licking and keep on ticking. I haven't enough time with Takasuki to judge but their build quality suggests great long-term stability and durability.

Phil

I owned the Audiopax 88 before I fully committed to Audion SET and PSET in my systems. The 88 is a beautiful sounding amp, though it is hardest to get deep bass to sound right. If you have speakers that have nothing usable below 40Hz or so, this isn't any problem.

The main contemporary problem with going Audiopax 88 is the sound quality of current production KT88 tubes. I was fortunate at the time to have an ample quantity of NOS British Gold Lion (Genelex) KT88s, as well as 1990s KR KT88s, ultra-screened from the old Tesla Vrovosic factory and relabeled KR. Both seriously improved the sound of the Apax 88 compared with any Russian production tetrodes. I let the Apaxes hang around awhile and pulled them out from time to time to try new tubes. They were pretty good with the Shuguang Treasure KT88, but still not up to NOS sonics.

So, that's what you have to consider going that route. Look at the price of remaining NOS Genelex/Gold Lion KT88s from the 1960s/70s or KRs from the 1990s, before making that commitment.

Phil

Yup, true. I've used OTL and SET on a very wide variety of speakers under optimal conditions for both amps. I'll put my statement cited in further perspective:

40, 30, 20 years ago, I would have (and did) recommend and own OTL tube amps for maximum transparency, speed and musicality, used with appropriate speakers, including over all the SET amps I'd gotten my hands on up to 1999. That's when I first happened upon an Audion SET 300B amp. And then further put original KR Enterprises 300Bs and well-chosen NOS input and driver tubes in it. With the emergence of objective high efficiency speakers (ala Zu) in the 2000s, the higher power of OTL became less necessary.

The Atmasphere amps are certainly transparent and fast, and I don't dispute the rise time measurements you site for them. But Audion SET amps are uniquely fast and transparent examples of that topology and I hear them as a notch above OTL.

Phil