Tube Amp Archive

If the output stage is cathode bias you can use the cap bypassed resistor to tube cathode node to raise the fils above ground. this has been around a long time as best I can tell.

Have you tried a 1 ohm power resistor after the bridge but before the first filter cap? A story years ago I modded a vc30 I changed the power supply caps to Poplypros. The amp hummed the transformer made noise. I realized the surge currents caused by the very low ESR caps were causing a DC inbalance...

Looking at the schematics I don't see the fil voltage elevated above ground. I think this would help with hum with the preamp and PI design of the amps.

Question does anyone know if there was a reason this was not done.