![Cool :cool:](./images/smilies/icon_cool.gif)
from my understanding the grid stoppers are there to prevent oscillation at high gain settings (like we have with the Sowter Output transformers)
try the potentiometer mod I did first, for the grid stoppers you would have to modify the PCB. worked for me.
and I can't remember any hum before, only the oscillation ...
Kubi would be the man to explain grid stoppers
![Surprised :o](./images/smilies/icon_surprised.gif)