The Right Power Amp:
  Single-ended triode; type 2A3 output tube, 6SN7 voltage amp/driver tube, & 5AR4 rectifier. Output level indicator is type 1629 'magic eye' tube, driven by a 6SL7. Output transformer is a One Electron type UBT-3. Power transformers and filter choke are Hammond's. The voltmeter shows cathode bias voltage of the 2A3; an indication of the health of output & rectifier tubes.