Found this circuit in an old Philips publication. It was intended as an amplifier stage for an audio oscillator but it looks like it could be used as the basis of a reasonably good audio amplifier. Cascoded long tailed pair input stage with current source in the cathode circuit. Second stage has an unused anode just begging to be used as a push pull source. Distortion figures look pretty good.
But besides having an enormous amount of gain, the output impedance is still about 1K (if I'm not mistaken...). It could be a good performer for 800 Ohm loudspeakers, which Philips manufactured in abundance in the 50's and 60's. They even made a very good 800 Ohm woofer, the AD5201A. But for the usual impedance loudspeakers, I think you would need an output transformer.
Attached is the complete article.
Attached is the complete article.
OP was talking about using it as a driver stage not an output stage. You aren't joking about enormous gain, 2-3000!
The input stage and driver looks familiar, reminds me on the Atmasphere M60:
https://www.diyaudio.com/community/threads/what-tubes-for-a-otl-tube-amp.161112/post-2087700
https://www.diyaudio.com/community/threads/what-tubes-for-a-otl-tube-amp.161112/post-2087700