11-17-08: Atmasphere
There could also be a preamp issue that has not manifested before. If you can get your hands on a DVM, check and see if there is any continuity (less than 1 ohm) between the connectors and the chassis.
" Sometimes if the chassis is only grounded through the wall and the circuit isn't grounded to it you can run into trouble. That's not so bad in an amplifier but in a preamp it can result in hum, even if it worked fine with other amps!"
11-13-08: Sbank
Abe, according to the preamp designer, "All of the rca's on the preamp are isolated from the chassis and connected vis the 8 ga. buss. The chassis is grounded thru the charger jack only."
Atmasphere,
Is it possible the preamp is acting like a big antenna?
I still think Amandarae is on to something about the SET inputs being more sensitive than the other Amps Sbank was using.
Sbank, did you ever connect a wire from the chassis of the preamp to one of the amps chassis?
http://www.audioasylum.com/audio/general/messages/52/525608.html