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Humming humbuckers...
Old 31st January 2013
Here for the gear
🎧 5 years
Humming humbuckers...


On my two guitars I noticed a strange behaviour, which keeps confusing me:

Guitar A: Two humbuckers, 3-way switch, 1 volume, shielded with copper foil. When plugged into the amp and having the overdrive channel selected, theres an audible hum when the volume pot is open. The sound of the hum changes when I turn the pot down, until it vanishes completely. When I touch any metal parts of the guitar (strings, bridge, output jack,...), the hum gets much quieter. The same thing happens when I touch any metal parts on the amp or pedal board.

Guitar B: Two humbuckers, 3-way switch, 1 volume + 1 tone; same behaviour as guitar A, except that theres no change in the hum at all when I touch metal parts, no matter if it's on the guitar itself or on the amp or pedal board.

On both guitars I checked the grounding with a multimeter and everything seemed ok. Strings/bridge, switches, pots and the shielding of guitar A are all grounded to the sleeve of the guitar cable.

Shouldn't guitar A make less noise because of the shielding?
Why do both guitars behave differently when touching metal parts on them, or even the pedalboard/amp?

Thanks for your help,
Old 31st January 2013
Here for the gear
🎧 5 years
Nobody got any ideas?
Old 31st January 2013
Lives for gear
baskervils's Avatar
Hard to say:

A) Does your amp have a ground switch?
B) Do you get radio freqs when your cable is plugged into the amp and you put your thumb on the exposed 1/4" cable?
C) Have you tried switching cables?
Old 31st January 2013
Here for the gear
🎧 5 years
Thanks for your input

A) It doesn't, but I tried taping the ground on the plug, which didn't change anything.

B) When I touch the tip of the cable it's kind of the same hum as I hear when the guitar is plugged in, only louder.

C) Yes, I have tried that and it didn't make a difference.
Old 31st January 2013
Here for the gear
🎧 5 years
If it goes away when you touch the bridge or cable sleeve, it's most probably a grounding issue.

I had the same thing going on. One thing I hadn't checked at first and eventually turned out to be the culprit, was the ground wire of one of the pups itself. Must've pulled a little too hard when I swapped the pup.

I had to take it out and remove some of the tape covering the wiring. I then saw that the pup cable's shielding wire had broken off right next to the solder joint on the pup's metal base. I was able to heat the metal up just enough to get the tiny wire end connected again. Bye bye, hum!

Thus: try and measure between a metal part on the pup itself (the screw poles, for instance) and the bridge or another metal part on the guitar.
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