I just bought a G3 series Randall 75 watt and there is a switch on the back that lets you lift the ground. What is the purpose of doing that? I don't understand. Someone help me.
A gronded line keeps things from shorting out, its whats the third prong on the plug, but if you plug it into an outlet that isn't grounded it can cause interference, so this can help get rid of unwanted interference.
i think it has to do with noise reduction and grounding issues. Switch it on when it buzzes sometime.
If you've got two amps hooked up together (a/b/y box or just a stereo pedal) one of the amps needs to be un-grounded, otherwise you'll get a loud hum. I think it's called a ground loop or something.

On old amps it was just used to ground the amp. Since most amps didn't have grounded plugs way back when, you needed to set the ground yourself by flipping a switch like that.
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