I have a Squier DJAV bass that has had some substantial ground/hum issues in the past. It had an Aguilar OBP-2 & at my home the neck pickup (only) hummed markedly. What stopped the humming is touching the toggle switch or my amp (a G&K MB-800). I just had my luthier remove the OBP-2 to simplify things (it sounded brittle anyway) and we put in new passive pots (only) @ 250k volume tone & blend--& it now sounds far less brittle with that rock hard ebanol fingerboard (it's unfretted). Problem is, in my home using my amp, the neck pickup only still hums! What stops it is touching the disconnected toggle switch or the amp head as before. This problem can't be recreated at my luthier's place. At his place both pickups hum (he admits he has a ground issue in his house) but not such that touching the inert toggle switch stops it. My luthier adamantly asserts that my trailer (my home) must have a ground issue, however, my Marcus Miller bass no longer hums. (That bass for a year has had a severe humming issue since installing an Aguilar OBP-2, & finally he found a frayed wire causing the issue.) If it was an internal trailer wiring issue per se BOTH jazz basses would him. The Marcus Miller is almost dead quiet now (unless the active treble pot's turned way up) the way it should be. With such a simple passive wiring configuration I don't know how 2 Carvin JVA pickups going to a series of 3 passive 250k pots could go wrong, unless the barrel output jack is shot? I took the liberty of sending out for a real Fender American Series neck pickup (only) to replace the noisy Carvin. I probably jumped the gun too fast & might find I wasted money to replace a pickup that's not actually causing the hum. I should ad that my luthier tapped the Carvin and found them too microphonic, & he thinks I should also get a fender bridge pickup too. I posted another thtead unquiring about differences in timbre in vatioys windings 7.4 ohms tp 8 ohms. Also, the Squier's electronic cavity has shielding paint, but the pickup cavities I'm not sure about.