At around the 39 minute mark Chris asked the question if anyone is listen to the Amp Hour using a tube amp.
Well normally I'm not but it prompted me to get out my 1928 Philips speaker (45cm diameter) and a tube amp I build for my crystal set using tubes from the same time periode as the speaker.
The tube amp has an external PSU as in 1928 these type of amplifier were often powered from batteries and PSU was not build in the amplifier.
See picture below.
cj