Rich; organic true balanced amp w good detail $6k

The amp is the end of the chain when it comes to differentially balanced or not, and if there is anything to the "SET" nature of your amps, it will not matter a great deal I expect. I am not a circuit specialist, but given the way that the circuit runs through the tube, I cannot imagine how the "fully balanced" will matter to a true SET - I imagine it will only matter if it is triode-ified push-pull, and even then, circuit implementation will matter far more than whether the amplifier circuit is fully differentially balanced or not (the next part of the chain is speakers, which will not care whether the amp was differentially balanced or not).

The VTL 450s (the old ones, at least) have a triode/tetrode switch on the back (do NOT switch while the amp is on - some speakers do not like it).

I'm auditioning a Pass Labs XA-30.5 with Silverline Sonata III, driven by an Atma-Sphere MP-1 MK III. Alan Yun voices his speakers with Pass Labs, so I thought I ought to hear this combo.

I'm also using Speltz Zero boxes and doubling the Sonata III nominal impedance to 16 ohms. Very nice change...more spacious, open and relaxed, while still retaining the punch and drive. I'm not sure I'll ever use the Sonata III without the Zeros.

The bottom line is the XA-30.5 now is providing only 15 wpc into 8 ohms...but what excellent sound is resulting! I'm playing at easily 89-90db peaks with apparently room to go (but I haven't pushed it yet).

The Pass is a velvet hammer (which is exactly how I described the Moscode 401HR paired with Von Schweikert VR4 Gen III HSE). The Pass Labs/Silverline combo is the best I've heard in my living room since the Von Schweikert/Moscode combo, and yes I'd say the Pass/Silverline combo is better. Great bass...deep, tight and solid. Electric bass lines are clear in the mix and easy to follow. In fact, I can't recall following electric bass so easily in the past. Mids and highs are equally resolved, and the highs display outstanding clarity and extension with out sibilance. Mids have very nice weight, punch and drive.

No, it's not tubes...not quite as holographic or organic, but it's close, and it provides many things tubes don't (or at least haven't in any of my systems). The amp has only about 30 hours on it, and already it's making an impression. Supposedly, it won't come into full bloom until 100-150 hours.

I went from an ARC VT130 to a BAT VK75SE. I later modded the BAT with V-Caps and a few other minor changes that significantly improved resolution, neutrality, dynamics, bass extension & control-- IMO putting the amp at par with a top OTL. There is no area of this modded amp that is not way over the top of the ARC VT series. The 75SE can be converted to a monoblock if desired. The amp has been in production for quite awhile, but with a lite rework it's pretty astonishing. And used examples are available below $5K.

I share Tvad's positive opinion of the Spletz autoformers. In my second system they do a nice job of marrying a 3wpc SET to Wilson Watt/Puppy-- a very difficult load. In the some configurations they can make a mid-powered tube amp sound like big monoblocks.

clayton m200s or m300's

Sutts, FWIW there are amplifiers out there that run as hot as OTLs. In fact, OTLs only run hot if they are class A, not due to the number of tubes. It has to do with the energy that is dissipated in the output section, not the number of tubes.

For example, the BAT VK-60 and VK-75 run *hotter* than equivalent-powered OTLs. The same is true of the push-pull Lamm- this having more to do with the power tube used by those companies as well as the class of operation.

Israel is getting an OTL for his own use BTW (one that is also fully balanced-differential). Coincidents have been an excellent speaker with OTLs for years.