Constant 60hz humming / buzzing from speakers Denon AVR-484

[nottoms]

Hi, I'm using a Denon AVR-484 receiver connected to my TV via optical cable.

While the humming has been there for quite some time it's recently started to annoy me quite a bit and was wondering if anyone would be able to help me out.
The humming comes from the speakers (not the receiver itself). Humming increases / decreases when I adjust volume, and goes away for some of the input settings(unfortunately not for the input I use it for). I've tried disconnecting all audio inputs so that just the speakers and the power cable are connected, that didn't eliminate the buzzing.
Also tried connecting the receiver to different power outlets to make sure there is no ground loop issues. That did not have any effect either.
Any suggestions to what to try next?

I realize it's a fairly old receiver and that I probably should replace it at some point, but I quite like it and would like to keep using it if possible.

 

[jsmithepa]

Since wo any input doesn't help, that means the prob is with the amp itself. There is (are) floating ground(s) somewhere in there, probably cold solder joints. If you insist, find amp stages grounds and add your own grounding. A schematic would help. Don't electrocute yourself. With an oscilloscope, u can find presence of 60hz ripples.

 

[americanaudiophile]

Since there are some inputs that don't have hum the cold solder joints would not likely to be in the amps.
If you want to try and fix it you can get the service manual here
https/www.hifiengine.com/manual_library/denon/avr-484.shtml
You could also use a different input that doesn't have noise. If the coax digital input doesn't have noise you could get an optical to coax digital audio converter.