Few weeks ago I bumped the cable plugged into my (passive) bass at the jack and it immediately started to hum on the spot like there is a grounding issue. It hums with either pick up on or both pick ups on when the tone knob is turned on in either situation. It stops humming when I touch the strings, the knobs or the bridge. Not seeing anything visibly loose, I figured it was the jack so I replaced that with a new one and it's still doing it. I've unsoldered and resoldered all the grounds to where they were and it's still doing it. I pulled the pick ups out and didn't see anything amiss there in terms of the leads soldered to the housing. Oddly enough it gets worse (louder) as I move away from my amp. Is it grounding or shielding or both or...? The fact that it was dead silent until I bumped leads me to believe its grounding. the fact that it gets worse as i move away from the amp tells me its shielding. Could it be one exacerbating the other? Thoughts and recommendations?