Guitar grounding issue?

[Luca Brasi]

Hi,

I use my Digitech GNX3 for recording and I'm having an issue with a guitar noise that might be grounding related.

When I plug my electric guitar into my GNX3 I get a loud hum that is only relieved by putting my hand firmly in contact with the strings or bridge. In most cases this is fine, but when I remove my fingers from the strings or my hand from the bridge, the noise is there and it ruins the take. I am running my guitar directly into the GNX3 and the GNX3 directly into my computer using a mono (two 1/4" male ends) to stereo 1/8" Y cord.

I've checked the guitar's electronics, all the grounding connections are good (the bridge and pickups are all grounded). This guitar does not have a hum when plugged into my amplifier, only when it's plugged into the GNX3. I also have a second electric guitar that does not have a hum problem when plugged into the GNX3. In all instances mentioned I used the same cable from the guitar to the device.

I've taken the GNX3 plug out of the outlet strip and inverted its position and replugged it with no difference in the noise. I'm wondering if anybody on this forum might have an idea as to what my problem could be. I wondering if it has anything to do with the Bumblebee caps that I installed in the guitar (but they work fine with my amp-no noise), however, my other guitar has the same cap in it and has no noise issues.

I am wondering if I have some sort of loop effect going on.

Thanks in advance!

Steve

 

[miroslav]

Which guitar makes noise....is it a single coil or HB?

This is nothing unusual...you add a pedal into your signal chain and all of a sudden you get hum...but only with some guitars/amps...etc.

Yes...grounding issues.

How to fix it permanently...?...that's often a witch hunt.

A simple temp solution I use is to take a ground wire with alligator clips on each end and find a clean metal connection on the device's case (a screw or jack)...and connect it to another device/amp case via the ground wire/alligator clips.

Ex:
I've connected the case of my powered amp to another amp next to it that wasn't powered up...and the hum cleared. I’ve also connected pedal case to pedal case…or pedal case to amp case….etc…etc…you just have to find what connection removes the hum.

 

[Luca Brasi]

Which guitar makes noise....is it a single coil or HB?

The guitar that makes noise has two Seymour Duncan PAF humbuckers. The guitar that makes no noise has two Seymour Duncan humbuckers plus an EMG single coil, no noise from any of those pups.

I hadn't thought about a temporary alligator clip ground. I'll try that when I get home tonight.

I also thought about getting a hum eliminator but don't know which one would be best; the kind that you plug the guitar into or the kind that you plug the unit's power cord into? Anybody with experience on these?

Thanks!

Steve

 

[Lt. Bob]

one thing ..... is the Digitech plugged into the same outlet as the recorder?
Sometimes if you plug a pedal into a different outlet than the amp it's into, you'll get a hum from a ground loop. You can fix that by simply plugging the pedal into the same outlet as the amp.
COULD be a similar issue here.

 

[Luca Brasi]

The pedal is not plugged into the same outlet as the amp. In fact, I'm not even using the amp; the pedal goes straight into my computer. The pedal and the computer are on the same power strip.

Steve

 

[ggunn]

one thing ..... is the Digitech plugged into the same outlet as the recorder?
Sometimes if you plug a pedal into a different outlet than the amp it's into, you'll get a hum from a ground loop. You can fix that by simply plugging the pedal into the same outlet as the amp.
COULD be a similar issue here.

And sometimes different circuits/outlets are problematic because the hot leg of the 120VAC in one outlet is from the other leg of the 240VAC supply from the other outlet. I run my whole studio from a single home run circuit I had installed when we built the house.