Get a multi meter and stick probes one into the neutral the other into the phase and measure for DC mV, and that’s what I did. I am not going to do anything more than what they suggested.
That’s pretty smart. :)
I never thought of that, as I was worried about the meter being damaged, but reading around the net it seems safe to do with a digital, and with a mechanical, just set it to the highest range first, then come down.
Glad you tried turning everything off.
One other thing you could do, is try moving your amp to another phase. Usually the circuits breakers alternate phase going down. So if your amp is now on the top breaker, try the second fourth or sixth down.