Kcarlile,

I'm running the high-level (speaker-level) inputs from a tube integrated. There is enough current to wake up the subs (green light on), but it's as though it takes a minute or so to have the driver warm up. Its a faint "mechanical noise"....I assume to be voice coil hum.

Are you running a reciever with subouts? If so goose your output to the subs.