P bass grounding

[Bassamatic]

This incredible myth possibly stems from the idea of the cable capacitance that exists between the shield and conductor. In some drug and smoke-filled room an ideal was hatched that shielding in a cavity is somewhat the same as in a cable and can suck your tone. Of course - in theory it is - but the capacitor is so infinitesimally small it can't affect anything short of radar.

OP - If you want to shield - do it when you are building it. Use the Stew-Mac copper foil with the conductive adhesive. Make sure ALL grounds go only to one place - such as a screw terminal in the cavity or to the output jack.

That being said, I have a P Bass that is wired with shielded cable instead of copper foil shield - between the pots and to the output jack. And it is DEAD DEAD DEAD silent even here next to my RF and hum spewing computer. The shield of each bit of cable is soldered to the pot case. It works.

 

[sissy kathy]

"Need" is highly debatable. Depending on who you ask, shielding is either completely and utterly useless, the greatest thing since sliced bread, or somewhere inbetween. Personally, I have never seen why people are so reluctant to shield. It's cheap, and only needs to be done once over the life of the instrument, so why not do it?

Line6man, I have been advised by someone I trust to take your advice. I'll shield the cavity w/copper as you suggest. Thank you for your input.

 

[khutch]

Yes, there certainly is some capacitance between the wiring in your bass and any shielding material you put in the cavity. It is probably only 1 to 10% of the capacitance per meter you get from your amp cable and your bass cavity is not many meters long but it is there. Is carbon paint better than metal in this regard? I don't know of any theoretical shortcut that would give us a quick answer. If I had access to a 3D EM solver I would be glad to run the numbers for everyone but I don't have access to any 3D EM solvers so I will leave that for some university student. The bottom line is that passive or active if you play your bass in enough different venues you will eventually run into one that will make you wish your bass were better shielded. Ten or twenty dB of noise suppression from a good shield is much more important than 1 or 2 dB of "tone suck" at 10 kHz where you bass generates little if any signal energy.

 

[ReidK]

I didn't think you needed to shield with split P humbuckers....

You do need to ground with the bridge, but I thought that was it...

Shielding the pickup routs is of limited value with humbuckers (it can help, because no humbucker is perfect), but we're talking about shielding the control cavity. Humbuckers don't help there.

Reid

 

[gidbass]

Shielding the pickup routs is of limited value with humbuckers (it can help, because no humbucker is perfect), but we're talking about shielding the control cavity. Humbuckers don't help there.

Reid

Ah, that makes sense.

Thanks for the clarification.