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
Enjoy,
TIC
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?