V4 PCB component repair/updating

[beedoola]

maybe you have a bad tube for channel 1? I've certainly had tubes where the heaters shorted to the cathode, and that made for a pronounced hum. that would also explain the interaction with the sensitivity rocker. since those are changing the resistance in series with the cathode bypass caps.

Thanks Steve. I'll swap out V1 and see if that fixes the hum.

****Update****

Swapping out V1 stopped the extra hum.