Amplifier Hum


Hi, I have a Parasound HCA 2200 II that has started to make a humming noise. The noise is coming from the amp itself not the speakers. It just started doing this but still seems to function fine. Previously it was dead silent. The amp has about 3 years of use on it. My question: Is it time to sent to Parasound for a tune-up or is there somthing I can check myself? (the amp is not under warranty as I'm not the original owner) Any help would be greatly appreciated.
Thanks
skeevay
Post removed 
Craig,

My DNA-2 transformer hums also. I've found that it only hums when one branch circuit in the house is turned on. The circuit is controled by a dimmer/timer. I'm not sure how exactly this might help but try and see is there is any correlation between the DNA hum and other circuits being on. BTW I'm getting my amp upgraded soon, please tell me it's worth it.

John
John; Yep-- the upgrade is worth it, IMO. After upgrade to Rev. A the amp has an incredible smoothness, liquid character, and naturalness that could be described as "tube-like" in the mids and low treble, but it still has the quickness and bass control of a big McCormack amp. Very musical. Cheers. Craig