Son of ben 60hz hum

[IgorAnnikov]

A friend got a son of ben preamp that I built and he says he is getting 60hz hum whenever he touches the bass knob. It's only that knob.
Any idea what the problem might be? It works and sounds great otherwise

 

[Cybercow]

Dbl-Check the solder joints on that bass pot. Sounds like it may have a cold solder joint if touching it produces a hum.

 

[Chuck D. Bones]

Also make sure that the BASS pot is making good electrical contact with the inside of the enclosure. If there is paint in the inside around the pot's mounting hole, then sand it off.