I've got a CE1000A and have a buzz/humm with no input connected and the amp's level controls do not affect it.
Do I need to work up to disassembling, cleaning, and replacing caps just as Kev has done?! Sounds like a bit of an undertaking.
It may also be as simple as loosing and retighting the screws that hold the board to the chassis. If for some reason one of the grounds has oxidized under the screw this may clear it up.
Otherwise it could be a bad capacitor which would have to be found and replaced.
The service manual for the CE series is avaialble on our web site at: http://www.crownaudio.com/gen_htm/legacy/legacamp.htm
Note: Inside an amplifier a pretty large electrical charge can still be stored even if the amp is off for some time. Care should be taken when working on any electronics.
Thanks for posting guys. I started poking around and R and R'd the input board, with the ribbon cable, and all is quiet!....for now that is.