Whirring, whistling sound from left speaker


When I turn on my preamp and amps, but with the preamp in mute mode, I hear a whirring, almost whistling-like sound from the left speaker for about 1 to 2 minutes. This happens whether I have a power conditioner connected to the amps or not. I have independant circuits in the house for the system. Both the preamp and monoblock amps are tubed. Any ideas why this is happening and whether it is something I should worry about?
znak_m
Sure sounds like a bad tube to me too. Do what Thorman said. Swap the left channel tubes with the right channel tubes and see if the noise changes sides.

Enjoy,

TIC
Hi : The only other thing I can think of offhand is your incoming power..I sometimes get some unpleasant noise usuaully during are heavy electrical usuage ..Its usually during real cold weather or very hot ( many air conditioners working )muggy days...For me its garbage coming in from the electrical comapany about 50% of the time..I have learned to just live with it.........