Einstein, Herbert and VH4 are creating their sound in the preamp with nuances and the bottom end created from the poweramp. A Class A amp like Schmidt creates its sound with a higher degree in the poweramp, its warmth and sonic vibe is more an interaction of the whole machine, which includes a tube driven reverb.
Additionally Peter has built in some really sophisticated stuff which makes the amp breathe in a very open sounding way. What you play inside will come thru the speakers, so its more controlable thru your playing but also pretty unforgiving.
As I've said in another thread - it is on the side of the spectrum - like fire and ice (which doesn't mean it has no gain or so) - hard to describe.
But then the big advantage is its multi channel design (with loop and reverb). While loads of class A amps sound amazingly well for styles like jazz/blues/fusion and have just one channel, Schmidt goes two steps further - lets take the clean channel f.i.
Normally you'd expect the channel to be clean, with Schmidt (and your (!) seletion of the powertubes) you have the option (with 6V6s) to get typical small wattage fenderesque blues-cleans from the amp - when the poweramp is cranked. And then, for a tad more gain you'd go to the second channel and add some dirt without needing a pedal. Still not enough? Well, there's a booster inside . . . Go back to EL34s and have a clean/clean with a sparkling reverb from channel 1 . . ..
There are a million sounds inside this machine, esp those which were not easily accessable with the other members of the Diezel family yet - thats why it makes perfectly sense to add this kind of amp to the portfolio.
You need SRV? Well . . .
You need AC/DC? Well . . .
You need Delta Blues? Well . . .
You need Knopfler? Well . . .
You need Rory Gallagher? Well . . .
You need Hendrix? Well . . . .
And if you want to rock, just put some EL34s inside, crank it, crank the gain - and rock.