The Berning 30/30w ZOTL amp has a push-pull output topology, using two of the 33JV6 tubes per channel. They are not, as I understand the circuit, wired PSET. It nevertheless is a clear and highly resolving amp.
Regarding the question of TVC: I headed down the TVC route in lieu of an active preamp about five years ago after I sold my crossover-based speakers and migrated both my systems to Zu. At the time I got the Django TVC assembled by DIYhifisupply, in the S&B TX-102 transformers option, with all internal wiring in silver/teflon. Shortly after that, the US importer shom I've known for over 30 years, was in California and stopped by with his first Music First sample and we compared them. Music First, the integrated products arm of S&B, calimed then that their own version of the TX-102 was in some unexplained way premium to the version they were then selling to other TVC makers, and as I understand it today, a Music First product is the only way a hifi consumer can buy a TX-102 based TVC new.
Regardless, the S&B xformers were and are among the best, and TX-102s including in Bent Audio, DIYhififsupply and other vendors' products were unconditionally excellent. The Music First TVC (what is now their "Classic") was very marginally, just perceptibly more resolving than the Django. It was a very small difference. And some of it could have been due to the Django's steel chassis against the Music First's aluminum. Switchgear, internal wiring and workmanship were fully competitive between the two, despite the considerable price difference (UK-made Music First more expensive).
At the time I had a variety of amplifiers and four active preamps on hand for comparison, three tube-based, and one the Audiopax solid state preamp on loan.
I liked the TVC, and still have the Django as my spare preamp. But it did not win out over my Audion Premier, nor my Klimo Merlino Gold, nor a Melody P1688 I was evaluating at the time. It did win out over my nearly 40 years old Stax SRA-3s tube preamp/headphone amp. I'll say more specifically that the TVCs -- neither of them -- were preferred to the active preamps with my Audion amps, which was interesting because of all the amps I had on hand at the time, the Audions had the highest input sensitivity, so even the +6db gain available wasn't needed.
The TVC did yield several sonic advantages driving Audiopax 88 tube monoblocks, and a pair of Quad IIs. Unfortunately, the input sensitivity on the Audiopax was very low, so the TVC couldn't drive them to full power with normal sources. At the time, to live with the TVC and the Audiopaxes for an extended period and drive them to full dynamic range with a TVC, I had a set of interstage xformers made from S&B TX103 step-ups, so that I could add another 6db of gain. Of course I had to be precise about impedance matching, but it worked with the Audiopaxes. On the Quad II, which have input sensitivity of 1.4v, I did very much like the refined presentation of the Django and Music First, and it has seemed to work well when anyone has brought a solid state amp to listen to.
So, on TVCs, I say your sound quality experiences will vary by power amplifiers. Into Audion Black Shadows and Audion Golden Dreams, the TVC sound is inferior to my tube-circuit active preamps, though I wish it were otherwise because the isolation and lack of an additional power supply definitely makes it easier to chase more noise out of an SET-based system.
Now, Spiritofmusic, on to your volume control range question. I get asked about this alot, so it bears explanation.
Your usable volume control range is not very much affected by the output power of your amplifier. Yes, with two power amps of same input sensitivity, the more powerful amp will deliver somewhat more power at a given volume control level. What you really need to pay attention to is the gain relationship between the preamp and power amp, and/or the input sensitivity of the power amp relative to the preamp's gain and therefore output.
For example: My Audion tube amps have input sensitivity of 0.7v, meaning a signal of 7/10ths of a volt will drive them to full power. Compare this to American amps that generally have an input sensitivity in the 1.5v - 2.0v range. You can see that, depending on the contour of a preamp's volume control and your sources, that generally if I use a power amp with 2.0v input sensitivity, I would get much more usable rotational range on my preamp's volume control. In fact I hint at this scenario in the discussion above. With a disc player having the standard 2v output, connected to a 0db gain TVC where all you can do is attenuate, I could not drive the Audiopax 88 amps to full power even with the TVC volume control turned all the way up, because the Audiopax's input sensitivity was greater than 2v. In a market where most power amps have 24 - 32 db of gain, the Audiopax 88 has only 18 db gain. On the other hand, the TVC set for 0db gain could easily drive the 0.7v input sensitivity Audion amps to full power with the attenuated output of a 2v out disc player.
So what to do when you use an active preamp? This is where input level control on power amps are helpful, because most gear has too much total gain in the chain. Right now, two of my three active preamps are fairly high gain -- the Klimo is 20db and the Melody 101 has 23 and 15 db options. But they each sound great with the Audions. The advantage is, my preamps are quieter than are my SET power amps (common for SET). So I can prioritize the gain in my quiet preamps over the gain in my noisier power amps by running the input level controls turned very low, effectively raising the input sensitivity by "throwing away gain" at the input level pot. This way, I get more usable rotation in my preamp volume control, and lower the system noise floor by reducing SET noise. It's not an amp power issue. I could put in an pair of 1200w McIntosh monoblocks with ~2v input sensitivity and have more volume control range than I'd have if my Audion amps didn't have input level controls, though there could be bigger consequences if the volume control were set too high. The point is, regardless of the power amp, you can choose a preamp/power amp combination that molds the gain relationship between pre/pwr to your operating advantage.
If the gain relationship or output/input sensitivity are not mated well, you won't get more useful rotational range from your volume control with a lower powered amp, but you might push the amp into clipping sooner. Make sense to you?
So if you want more usable range out of your preamp volume control with a given power amp, you either have to choose a preamp option with less gain or need a way to throw away excess gain via input level controls or find lower-output sources to eliminate the problem. A TVC gives you a 0db gain option or at most +6db optional, to reduce system gain, so if it in fact sounds as good or better than a higher gain active preamp, you will get what you're seeking irrespective of the power amp's output.
Phil
Regarding the question of TVC: I headed down the TVC route in lieu of an active preamp about five years ago after I sold my crossover-based speakers and migrated both my systems to Zu. At the time I got the Django TVC assembled by DIYhifisupply, in the S&B TX-102 transformers option, with all internal wiring in silver/teflon. Shortly after that, the US importer shom I've known for over 30 years, was in California and stopped by with his first Music First sample and we compared them. Music First, the integrated products arm of S&B, calimed then that their own version of the TX-102 was in some unexplained way premium to the version they were then selling to other TVC makers, and as I understand it today, a Music First product is the only way a hifi consumer can buy a TX-102 based TVC new.
Regardless, the S&B xformers were and are among the best, and TX-102s including in Bent Audio, DIYhififsupply and other vendors' products were unconditionally excellent. The Music First TVC (what is now their "Classic") was very marginally, just perceptibly more resolving than the Django. It was a very small difference. And some of it could have been due to the Django's steel chassis against the Music First's aluminum. Switchgear, internal wiring and workmanship were fully competitive between the two, despite the considerable price difference (UK-made Music First more expensive).
At the time I had a variety of amplifiers and four active preamps on hand for comparison, three tube-based, and one the Audiopax solid state preamp on loan.
I liked the TVC, and still have the Django as my spare preamp. But it did not win out over my Audion Premier, nor my Klimo Merlino Gold, nor a Melody P1688 I was evaluating at the time. It did win out over my nearly 40 years old Stax SRA-3s tube preamp/headphone amp. I'll say more specifically that the TVCs -- neither of them -- were preferred to the active preamps with my Audion amps, which was interesting because of all the amps I had on hand at the time, the Audions had the highest input sensitivity, so even the +6db gain available wasn't needed.
The TVC did yield several sonic advantages driving Audiopax 88 tube monoblocks, and a pair of Quad IIs. Unfortunately, the input sensitivity on the Audiopax was very low, so the TVC couldn't drive them to full power with normal sources. At the time, to live with the TVC and the Audiopaxes for an extended period and drive them to full dynamic range with a TVC, I had a set of interstage xformers made from S&B TX103 step-ups, so that I could add another 6db of gain. Of course I had to be precise about impedance matching, but it worked with the Audiopaxes. On the Quad II, which have input sensitivity of 1.4v, I did very much like the refined presentation of the Django and Music First, and it has seemed to work well when anyone has brought a solid state amp to listen to.
So, on TVCs, I say your sound quality experiences will vary by power amplifiers. Into Audion Black Shadows and Audion Golden Dreams, the TVC sound is inferior to my tube-circuit active preamps, though I wish it were otherwise because the isolation and lack of an additional power supply definitely makes it easier to chase more noise out of an SET-based system.
Now, Spiritofmusic, on to your volume control range question. I get asked about this alot, so it bears explanation.
Your usable volume control range is not very much affected by the output power of your amplifier. Yes, with two power amps of same input sensitivity, the more powerful amp will deliver somewhat more power at a given volume control level. What you really need to pay attention to is the gain relationship between the preamp and power amp, and/or the input sensitivity of the power amp relative to the preamp's gain and therefore output.
For example: My Audion tube amps have input sensitivity of 0.7v, meaning a signal of 7/10ths of a volt will drive them to full power. Compare this to American amps that generally have an input sensitivity in the 1.5v - 2.0v range. You can see that, depending on the contour of a preamp's volume control and your sources, that generally if I use a power amp with 2.0v input sensitivity, I would get much more usable rotational range on my preamp's volume control. In fact I hint at this scenario in the discussion above. With a disc player having the standard 2v output, connected to a 0db gain TVC where all you can do is attenuate, I could not drive the Audiopax 88 amps to full power even with the TVC volume control turned all the way up, because the Audiopax's input sensitivity was greater than 2v. In a market where most power amps have 24 - 32 db of gain, the Audiopax 88 has only 18 db gain. On the other hand, the TVC set for 0db gain could easily drive the 0.7v input sensitivity Audion amps to full power with the attenuated output of a 2v out disc player.
So what to do when you use an active preamp? This is where input level control on power amps are helpful, because most gear has too much total gain in the chain. Right now, two of my three active preamps are fairly high gain -- the Klimo is 20db and the Melody 101 has 23 and 15 db options. But they each sound great with the Audions. The advantage is, my preamps are quieter than are my SET power amps (common for SET). So I can prioritize the gain in my quiet preamps over the gain in my noisier power amps by running the input level controls turned very low, effectively raising the input sensitivity by "throwing away gain" at the input level pot. This way, I get more usable rotation in my preamp volume control, and lower the system noise floor by reducing SET noise. It's not an amp power issue. I could put in an pair of 1200w McIntosh monoblocks with ~2v input sensitivity and have more volume control range than I'd have if my Audion amps didn't have input level controls, though there could be bigger consequences if the volume control were set too high. The point is, regardless of the power amp, you can choose a preamp/power amp combination that molds the gain relationship between pre/pwr to your operating advantage.
If the gain relationship or output/input sensitivity are not mated well, you won't get more useful rotational range from your volume control with a lower powered amp, but you might push the amp into clipping sooner. Make sense to you?
So if you want more usable range out of your preamp volume control with a given power amp, you either have to choose a preamp option with less gain or need a way to throw away excess gain via input level controls or find lower-output sources to eliminate the problem. A TVC gives you a 0db gain option or at most +6db optional, to reduce system gain, so if it in fact sounds as good or better than a higher gain active preamp, you will get what you're seeking irrespective of the power amp's output.
Phil