DC Heaters for V1 & V2

[okgb]

120 , 180 a little hard to tell but the grounding helped the typical 60hz type hum , that the rest is now noticable
I did try running it with only the last tube[stage ] and still the hum and although i tried swapping tubes I didn't
use any older or nos type tubes .
Ignorant question , but how do you d.c. elevate the heater ground ? I also didn't try a hum balance type control
100ohm pot ?

[Smitty]

A big hint here if using vintage power trannies and not a tube rectifier (i.e. you have a free 5V AC winding), a bridge recitifier using schottky diodes into about 10,000uF off the 5V AC winding gives 5.95 to 6.0 V DC, just right for heaters for the first stage or 2 of the guitar amp.

I'd like to try this and see how close I can get to 6V from the 5V 2A winding on a princeton transformer. Seems like the right schottky will make all the difference. Any suggestions for which schottky will have the lowest forward voltage drop and still be able to handle the current. Seems like inrush current would be the main consideration with a 10,000uF cap.

[Chuck H]

If you have any way to reference the hum frequency that would help. If it's not 120Hz (power supply) the typical hum reduction methods are moot because we don't know the source without further trouble shooting.

DC elevating the filament supply is probably done most easily with a voltage divider off the main B+ supply node. You would configure the divider for maybe 30V to 50V and bypass the dropping resistor with a 100uf/100V cap (overkill but that's alright). Move the CT for the filament wind from ground to the divider node. Your preamp already has a "bleeder" resistor, R34. This could probably be lifted or removed if you do the elevated filament CT since it also offers a voltage discharge path. But... Unless the hum is power supply related the DC elevated filament CT won't help.