If the TS has a multimeter (a VOM or a digital VOM) then a whole lot of information would be available and correct answers provided.

I do. Please tell me how.

 

Measure the DC voltage between the top of the control and the circuit common, (power supply common). And also the DC voltage at the amplifier IC input when the control is turned up so that the sound stops.

 

Yes depending on the offset polarity.

Yeah and the usual fix for AC signals is to use a coupling capacitor, which usually helps a lot.

 

Thanks everybody! A 1μF capacitor before the pot took care of the problem!