I recently bought my first bass, an ESP, off of craigslist, and I'm having a problem with the tone knob crackling. When plugged in and playing, the tone knob crackles whenever I turn it. If there isn't a note playing, it'll turn silently; when a note is played lightly, it'll crackle lightly; when a note is played loudly, it crackles loudly. Any ideas as to what might be wrong?
The wiring leading to the knob is probably loose, unscrew the knob and give er' a look, if you see that the cable is loose you can try to pop it back into place or if that scares you take her to a luthier and he'll get that sorted out.