I have an old Jackson/Charvel bass that someone hacked some Jackson active pickups into. I always liked the sound of the bass, but it always had an annoying buzz when I turned the tone controls up all the way. After I did some recording the other day I thought that I should try completely shielding the control cavity with copper tape. Now the noise problem is completely gone!
Funny, twenty minutes of effort eradicated years of being annoyed and not understanding why it buzzed. I tried grounding the bridge, not grounding the bridge. Shielded the pickup cavities, everything but shielding the control cavity. I guess for some reason I was thinking that the active pickup circuitry itself would not pick up extraneous noise. Live and learn!