Why is the guitar amplifier acting like a radio when I touch the volume knob


I just bought an acoustic/electric mandolin (Ibanez M511SE-DVS) that I decided to test out with the only guitar amp that I have (a Baja BG-10). It works fine, but I noticed that when I have my finger on the volume knob, I receive (what is most likely) an FM signal to a local radio station.

Given that I don't have a background in electrical engineering, in layman's terms what are the reasons that a guitar amplifier would pick up a radio signal and feed it back through the output (speaker)? This behavior only happens when I touch the volume button.

Best Answer

The capacitance from the volume control knob through the pot is large enough to allow RF to couple through - from your body, when you touch the knob - to the volume control circuitry, where it gets rectified/detected (turned into an audio signal) and sent through the rest of the amp to the loudspeaker.