Something wrong with my Gfa-555?

[inson71]

I have a Denon AVR-3806 which sends the front left and right signal via the pre-outs to my Adcom Gfa-555. It also sends the rear and surround signals to two Adcom Gfa 545s (I am runnig 7.1). I have recently noticed that my front right and left speakers (RTI 8s) have a faint hum in both the midrange drivers and the tweeter. My rear and and surround speakers produce no such hum. I swapped the 555 with a 545 and the buzzing vanished from my front speakers. I then unhooked the inputs from my 555 with only the speakers connected and the hum disappeared. Is this ground loop noise coming from my 555 or could there be something wrong with the 555's inputs? Again both 545s are dead quiet. It seems the 555 just doesn't like my Denon's pre-outs. Any help is greatly appreciated.

[inson71]

Hmmm... I guess it's off to the shop. I have tried everything I can think of to fix the problem. I even put a ground loop isolator between the Denon and the 555, but that only made the problem worse. Arghh.

[george daniel]

Maybe I misse something, but did you try disconnecting you cable(catv) completely? If not, you might wanna' try that.

[inson71]

Thanks for the reply. Yes, I did unhook my Directv satellite receiver completely from the system. I still had the same humming problem.

[thsmith]

So the 555 only hums when connected to the mains ?

Are the 545s connected to the same outlets as the 555 ?

I would think if it was the amp the hum wherever follow where you connected it.

Have you added any other components your system lately ? Might try putting a plug that takes 3 prongs to 2 prongs, a ground cheater plug until you isolate the gound problem. FOr the CATV box you have to diconnect the cable from the CATV box as well not just unplug the CATV box.

[inson71]

The 555 does not hum in the mains when nothing is connected to the 555's inputs. It hums when I connect any of the pre-outs of the Denon 3806 to the 555's inputs.
The 545s are in the same outlet (Panamax 1000+).
It seems the hum does follow the amp no matter which pre-outs from the receiver are hooked to its inputs.
I have completely unhooked the directv receiver from the system (power cord, coax, and hdmi cables).
I will try the cheater plug on different components to see if that works.
Thanks, thsmith!