Buzzing When Not Touching Strings

[LeonD]

My main bass has two humbuckers, one volume, one tone, a three way switch and passive electronics. The control cavity including the cover is shielded with foil.

I notice that when I take my hands off the strings, I get a buzzing sound thru my amp. I did this in my house but I thought it was because I have crappy electricity in my home (no grounds). But I was in a new bands practice place yesterday and I noticed the same buzzing sound.

Any idea what I should check out first?

Thanks,
LeonD

[Floridabwoy]

Bad ground. Have someone look at your jack.

My buddies house has bad electricity too. I have to play an active, or make sure I am wearing sneakers because the passives actually shock me.

[JFace]

It's possible both of your facilities have bad grounds. My basses have the best grounding I could possibly wire up, and they still buzz slightly when I'm not touching the strings. If this isn't the case, you may have a bit of resistance in your shielding. Be sure your shielding, your pots, and your bridge are all grounded.

[bassbenj]

Originally Posted by LeonD

My main bass has two humbuckers, one volume, one tone, a three way switch and passive electronics. The control cavity including the cover is shielded with foil.

I notice that when I take my hands off the strings, I get a buzzing sound thru my amp. I did this in my house but I thought it was because I have crappy electricity in my home (no grounds). But I was in a new bands practice place yesterday and I noticed the same buzzing sound.

Any idea what I should check out first?

The hum when not touching strings thing is almost always a shielding problem. Since you have foil shielding then I'd look for the connections to that foil. Measure resistance from outside metal of the jack to various other places on the foil. All should read a very low resistance. If the foil is not properly grounded (called "floating") it will not shield the circuits properly. If the foil is copper, grounds should be soldered to it and if it's aluminum, connections are usually made with screws through the foil into the wood with lock washers with those "teeth" that bite into the foil. If all that seems in order then you have to look to see if the foil extends over the entire circuit and wires. This includes shielding over the wires going to pickups, the three way switch (if outside the cavity) and foil in the bottom and sides of the pickup cavities (you obvious can't shield the tops).

Once all wires and electronics are as totally enclosed in foil as possible there should be no change in hum levels when you touch ground (strings etc) if foils are all properly grounded.