Quote Originally Posted by Light Dependant Resistor View Post

More or very problematic grounding, needs further methods of isolation, and
to the rescue are loop breaker circuits. http://sound.westhost.com/earthing.htm

Cheers / Chris
Keep up Chris, I've just explained all that to the technically challenged*!
On the bench I have temporarily disconnected the mains earth to isolate a hum problem once or twice, but that is SO dangerous in general use. Do not try this at home, kids.
* That is, even more than I am!