On Mon, 4 Jan 2010 07:00:44 -0800 (PST), Tim
wrote:

it's a good gig for them but event the patrons come and ask them
"what's the hum?" They don't know, I don't know.

I'm with Jack on this one - probably the lights. Bassy had a good
suggestion for a power conditioner and they are relatively
inexpensive.

Tha being said, it could just plain flat out be dirty power and/or low
voltage when everything is plugged in. I'd bet money the circuit
breakers are corroded - had that happen here at my house when we first
bought it - took me about a week to figure out why my MacIntosh 50s
were humming like crazy.

The only thing to do is to either condition the power which may or may
not help or supply a seperate source of power for the amps.