I looked at the back of my peavey 5150 (2x12 combo version) and saw a switch that had a positive setting, a 0 setting (in the middle), and a negative setting. Next to the swithc it reads "GND.".

What does that mean?
Most of the time it should be left in the center position. It's a ground lift switch, the idea is to get rid of noise from ground loops...like if you're playing through multiple amps simultaneously and getting humming noises as a result. If you lift the ground on an amp when it's just being used on its own, there is some risk of electrical shock.
Means you don't have new gear right now.
Quote by FEngHLyan

She will join the prom.

She insists to wear this lights.

I don't think so.

How can I persuade her?
Well I'm not playing throught multiple anything. Just guitar>cable>amp.

I'll switch it to 0 just because though if thats whats recomended.
It's also good on stage, if your amp, is plugged into a different circuit than your PA.. You haven't lived until you're holding your guitar... walk up to your mic, and a 3 inch blue spark shoots from the mic to your teeth...... That'll wake you up...

If your amp is humming a bit.. move the switch till it stops... if it doesn't stop.. check the mic with your hand first... it'll still bite.... just not as hard...
I Play Guitar
Some Like it
Some don't
I don't care
Beats Workin'
I like to think it means 'Guns, Nukes, Decoupage.' An efficient way of dealing out one's wrath with bullets, radiation and brightly coloured paper cutouts.

But it's probably a ground lift switch.