Buzzing on GT10B w/ Elixirs

[Octavian]

Here's the situation: I put a new set of Elixir nanoweb strings on a Fender '62 RI. I started messing around with some effects on a GT10B and was listening through headphones. All of a sudden, I'm getting a gnarly inconsistent buzz.

I replace cables. Same problem.

I switch outlets. Same problem.

I discover my finger is touching the magnet at times on the pick-up. That is causing the buzz.

I plug the bass into an amp. No buzz.

I plug the bass into a headphone amp. No buzz.

I plug the bass into the GT10-B. Buzz.

I put my barefoot on the GT10-B. Buzz is greatly reduced to quiet hum.

Soooooooooo...any suggestions on how to fix this?

[gumtownbassman]

Grounding, there is a grounding screw on the back of the GT-10B.
The GT-10B power supply has no ground connection like an amp does, so it needs to be plugged into something grounded (like an amp even if it is off and only plugged into the wall).

[Octavian]

Thanks. Forgive my electronic ignorance, but am I running a wire (of what gauge?) from the grounding screw to...?

[gumtownbassman]

Gauge doesn't matter, just connect from the GT-10B chassis to something already grounded.
You could just use an ordinary guitar lead plugged from the GT-10B to an amp already plugged into the wall socket.
Another mod is to change the power unit's mains plug for a 3 pin grounded type, and run a wire from the ground pin, taped to the cord to the GT-10B, with a ground lift switch inline.