[mrlizard]

Removing the earth on audio gear is usually fine, because its all generally plugged into one main plug socket and the earths are connected to each other via audio cables, so you're still technically earthed somewhere. if you remove an earth from something like a computer, its not earthed anywhere else, if it developed a fault and the casing became live, you could get a shock.

Its even more dangerous with valve amps because of the huge voltages. Sweaty hand on a mic, sweaty hand on guitar strings, fault in the amp you're toast. But if you've got a line out of the amp plugged into an another amp that is earthed you'd be fine.

I've never had to remove an earth to get rid of a buzz, if everything is earthed at the same point it's usually not a problem.