Simple circuitry, like from the thirties! Never mind fifties. There is a good reason those theater amps from that era fetch such high prices.
My little Chinese 2A3 SET surprised even me last night. A friend, Dmitry on the forum, was over and we decided to play some rock instead of jazz. Even the complexity of Black Magic Woman on Abraxas was clear as a bell at around 95db. I was appollogetic before I started playing LPs. I thought I should have had at least the Wrights hooked up.
I guess there is something to Ron Welborne's favor of SS rectification that allows the 2A3 to hold it's power level without sagging on the strong peaks. If the music was compressed, I couldn't tell.
The quote from the Khorn manual is circa 1977 BTW.
Rick