Hi Bruce – As you say, Jordan is indeed the man – But as to valves -
À chacun son gout – Had a chap in the other day who wanted me to ‘service’ his valve amplifier although there seemed nothing wrong with it. He went on to talk about eigentones, chromium plating, ceramic valve holders, ultra-linear problems and why valves had to be Mullard, as Russian ones seem to have a ‘Putin effect’ where severe distortion is evident, even to the totally deaf.
Remember knocking up a push/pull amp a year or two back using a pair of PX4 (directly heated triodes from the 30s where cathodes looked like toaster elements) with 500v HT and grid drive of some 150 volts. Coupled up the scope and got 7.5 Watts sine max before the waveform curled a bit.
Now seriously into WW2, used a RK34 power RF double triode with anodes as top caps - Quality fine but again lacking in watts.
Did another one with a pair of WW2 '807' Beam Tetrodes for a guitar chum. They were rated at 150 Watts individually class C but were total rubbish in Push/Pull class AB - Fiddled with the bias between classes but could hardly get 30 Watts out of them - Another failure.
Best one I ever did was back in ’73 with 8 x PL519s push/pull on 600 volts HT – Checked out at something over 1Kw before the sine wave flattened but didn’t have the speakers to really groove as worked in a Telly shop with telly speakers.
Subsequently went for transistors and with Silicon, eventually got the watts at rather lower voltages.
Radiograms are simply horrid, never made a decent easy pound with one - Chris.
