Luxman L509X owners - Question about Main In

Hey there...

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.

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Showing 1 response by ricred1

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?