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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.

Thanks!
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6 responses Add your response
dpac996's avatar
dpac996
676 posts
 
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

erik_squires
15,657 posts
 
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
ricred1
1,976 posts
 
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?
jsqt's avatar
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jsqt OP
117 posts
 
Thanks for the feedback... It does appear to have gotten worse the more I pushed things around back there. Now it is audible when watching a normal TV show, etc in the background. 

@dpac996 , Are you saying run from the preout on the 509X directly into the Main In, like a loop? So like play music from the DAC plugged into BAL 1, run a plug from PRE-OUT to the MAIN IN jacks right next to it? Will that damage anything, or at the very least tear a hole in space and time?

@erik_squires there is no coax in my system unfortunately, just a whole bunch of DACs, amps, Apple TVs, Orbi satellites, Hue Bridges, and the like. It is quite a mess behind my BDI cabinet but it seems like I may have to start from scratch today unplugging things to get the bottom of things.

@ricred1 - so just run a wire from the thumb screw on the AVM 60 to the screw on the 509X? I will try that too, thanks!

Anyone have experience with the Emotiva CMX-2?
erik_squires
15,657 posts
 
The CMX-2 is great for DC issues, ground loops not so much.



dpac996's avatar
dpac996
676 posts
 
@dpac996 , Are you saying run from the preout on the 509X directly into the Main In, like a loop? So like play music from the DAC plugged into BAL 1, run a plug from PRE-OUT to the MAIN IN jacks right next to it? Will that damage anything, or at the very least tear a hole in space and time?

YES. Totally fine. Just engage the "seperate" button and you are good to go. If no hum, you know 100% immediately nothing wrong with the 509 and that the problem lies with the interaction of mixed grounds with the home theater gear; This kind of stuff is a large reason why I have separated the home theater from dedicated 2 channel playback. It has been my experience over the years that you only get sub optimal sound on both fronts; YMMV!
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