Hi, I recently rehabed an old bass I got for free. I intalled a Seymour Duncan Basslines Quarter Pound pickup, along with 2 250k audio taper pots, and a switchcraft jack. Upon completion of the wiring (I'm more or less a novice at wiring), I plugged the bass in and when i wasnt touching the strings there was humming. I sheilded the cavity with copper tape, and i ran a ground wire from the jack to the underside of the bridge, and i dont know what else to do to eliminate the hum. Any suggestions? P.S- Would a picture of the cavity help at all?