I own a 509X that I bought used back in August '18. I recently picked up an Anthem AVM 60 and I'm running the main pre-outs into the RCA "Main In" (HT bypass) to run left/right on home theater. However I am noticing a faint 60 cycle hum from the mains (very sensitive La Scala IIs). I do not hear any noise at all from the other speakers in the HT system, which are running from a Monolith 7X amp.
If I hit the "Separate" button on the 509X (using the internal pre) the hum is not there - it is ONLY on the Main In when the "Separate" button is engaged. When I plug the same Anthem pre-outs into the Line In input of the Luxman, there is no hum.
My worry is that this is an amp issue with the Main In input/preamp bypass function, as I can't replicate it in any other inputs. Is it possible there is an issue with the Main In/bypass input? I hate to have to send the whole thing off to be looked at, and in theory I could bypass the 509X for HT altogether and just run my mains from the Monolith (will have to add another 2 channel amp for Atmos speakers). But I'd like to know if there's an issue with my Luxman.
Try running your pre out directly from 509 to the main in on the 509. Then hit the seperate button. I highly doubt there is an issue with 509. HT gnd loops are notorious for weird issues like this
One notorious source of ground loops is incoming coaxial cables. Try disconnecting any in your system. If that solves your problem, get a ground loop blocker for it: https://amzn.to/2JT8EQm
I had the same problem in my system when I used the HT bypass. I ran a six inch shielded wire from the ground on my 3-channel ATI amp to my Marantz AV preamp and the "ground loop hum" was eliminated. Is there a ground connection/screw on your Anthem AVM 60 and 509X that you can connect a wire to?
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