I've tried the Jazz and Precision bass American Deluxe basses and they are awesome instruments, but many are laden with ground noise and some even crackle. Thanks to this forum (and a brain-picking session with my tech Dan at DGN Guitars while my 5 string bass was in his shop for a coil-tap switch for the MM pickup on my Cort GB75) I got on board with suggestions how to shield my electronics. I bought an ADP, had a problem and returned it and then had the same problem on the next one so I called Fender and later read here about how they helped other members with their hum problems. They wanted me to take it to a regional service facility. After opening the control cavity it was no surprize to find no shielding whatsoever. Same thing under the rear J pickup. If I took my hands off the strings the noise was unbelievable and made worse if you were playing and accidentally touched the poles on the J pickup. That was some really wild hum! Anyway, someone here suggested in one of the threads using the conductive shielding paint and it made sense to me since I know my older deluxe Jazz basses had that. Apparently Fender forgot to shield all these new basses (sure they did) and a recall is certainly imminent. Rather than wait I bought the paint from Stewmac and used a hair dryer in between coats - you need a minimum of three coats. That speeded up the paint process. My tech said NOT to paint inside the jack cavity - risk of grounding wrong wires he said. Anyway, got that all done and back together and the bass was better, but not perfect. Having already had this problem on my modded Jazz bass I opted to install a brass cavity ground plate I bought from darren riley (he stocks ALL Fender parts and ships same day priority). One solder connection to the cavity ground and the plate underneath the rear J pickup was installed. My bass is dead quiet and I am enjoying it for the first time. If your Jazz bass still has some hum after shielding I would suggest a brass cavity grounding plate under both pickups. You might accomplish the same thing by grounding the pole pieces with a strip of copper and a wire to the cavity ground. That was also suggested here. I had no problem with the Pbass pup so I opted not to install the grouding plate under that pup. Since mine ain't broke anymore I'm not fixing anything else. I am grooving and happy I did not change the pickups or preamp out. This cost me about $40 in parts and is IMHO the best alternative out there if you like your new instrument. These are the best suggestions I could find, they worked and I hope they will help others end their frustration and begin their bass bliss.