🚀 go-pugleaf

You say your boom box audio contains sound from a nearby radio station
all the time, regardless of whether it's tuned to a station or playing
a tape or whatever?
  
I'll bet it's a very nearby AM station.

First step would be to get some 0.005-uF capacitors (not critical value)
and put one across each speaker and one across the volume control.
I'm thinking that something -- probably the speaker wires -- is acting
as an antenna and the AM radio signal is getting demodulated in the audio
section. ... Put a capacitor across the power supply input, too, if you're
using an external DC power supply.