Hi,\n\nThis ended up being a longer post. But I think I've covered all the details. Here goes.\n\nI got the 6700 in October 2020. It's currently powering a 5.1.2 setup I upgraded from a Yamaha RX-V685. And wanted to future proof things. Overall it's worked fine. But, a couple weeks ago, I started noticing a random low volume "hum". Random as in it doesn't always occur. This is how it occurs.\n\nI turn everything on to watch a show. That includes; Denon X6700H, Apple 4K TV box, and LG CX. There is a also a PS5 and AT&T TV box that sometimes also gets powered on. The Denon will make that "click" sound to indicate the speakers are getting powered. This is when I might hear that low "hum" sound coming from the center speaker. It does not always occur. It can be hard to hear if other things are running in the background, like the wall AC, my computer, and my cats. It will seem to go away on it's own within a hour or so.\n\nThe previous week it happened a few times when we sat down to watch something. I tired turning everything off and then on again, and it went away! But when it happened again, this didn't work. Another time it happened, I tried disconnecting the Center speaker. The hum went away. And so did the rest of the sound from the speaker. When I reconnected it, the hum was gone! But when it happened again the next day and I tired disconnecting, then reconnecting the center speaker, it didn't work to fix it.\n\nEarly on Friday it happened and I tried connecting the Right Front speaker to the central channel. Now the Front Right speaker was making that "hum". This makes me think it's something with the channel output on the back of the unit.\n\nIt happened last night when we sat down to watch Wanda Vision. We were either watching it on Disney+ on the Apple 4K TV or the LG CX app. The "hum" is not affected by the volume setting on the Denon. It can be heard if the volume is muted. So it can be more noticeable during the quite moments. Not so much when there is a lot action. I was annoyed. But my wife didn't notice it. When the episode was over the "hum" was gone. Watching other things sounded normal.\n\nToday on Sunday it happened again when I turned everything on. This time I tried to test a few things. This time I went around to every speaker to listen to hear if they were emitting the "hum" or not.\n\nFL -no\nFR - no\nCenter - yes\nSurround Left - yes\nSurround Right -no\nFront Presence Left - yes\nFront Presence Right - no\nSub - I forgot to listen to that. Opps\n\nPutting Receiver on Mute I still got the "hum". Volume doesn't affect the "hum". Going to the Denon Settings screen, I noticed that the "hum" can vary in volume slightly. When I'm on a screen that has selectable options and I highlight one of them, then it's slightly louder. If I select a greyed out selection it's now slightly quitter. This was at one of the HDMI settings screen. I connected my headphones to the Denon to check to see if it was coming through my headphones. It did not. It sounded normal, with the show I was listening to. When I unplugged the headphones to listen to the speakers the "hum" was gone! Hmmmm. I shut everything down, then turned it back on, and the "hum" was back. I took the headphones adapter, without the headphones and plugged it in. That turned off the speakers. When I disconnected the adapter, the "hum" was back in the speakers. I then connected the headphones to that adapter and plugged it in the Denon and listened to something for a little bit. Maybe 30 seconds. I then unplugged the headphones and listened to the speakers and the hum was gone! \n\nAnd to add, I got in contact with Serg at Scan Audio Services in Van Nuys on Friday. I had emailed his place with a detailed email explaining most of the above. He said he thinks there is something going bad on the Denon's motherboard, and that the MB will need to be replaced. He no longer does warranty repair for Denon. But he suggested to ship it to Radio United in New York to get warranty repair. I asked what about taking it to George Meyer in LA, for they do warranty repairs for Denon. He cautioned that there may be a long wait on parts from their shop. And that it would be better to let a bigger repair place, like Radio United handle it. I had also talked to someone from Crutchfield tech support earlier trying to figure out what was wrong and they highly recommended Radio United for repairs. They also warned about NOT using some repair place in New Jersey for they were terrible about repairing equipment. But he couldn't remember the name. Could that have been Panugry?\n\nDo you guys have any suggestions? Is there something I can try with my setup that might be causing this? Like could this still be a grounding isse? Or is the motherboard on my Denon going bad and will eventually need to get repaired at one of Denon's Warranty repair places?\n\nIf I do take it to a Warranty repair place should I take it locally? George Meyer is 11 miles from me. So no FED EX shipping charge. But if they have to order parts, how long is the way?\n\nOr do I ship it to Radio United in New York? For the turn around time may be faster, since it's a bigger repair facility.\n\nIf my unit is a lemon, would either place be able to communicate with Denon to have Denon send me something to replace the 6700? I assume a refurbished unit? Or would it be brand new? And if it sold out in most places, I wonder how much longer that will take?\n\nFor now I'm going to see if the headphones plugging in and out will work. EDIT : Unfortunately this does not always work. I just tested it again after posting. Darn. But if it's a part going defective, then I imagine the issue will get worse. Fortunately I still have my Yamaha RX-685, so I could use that when I send the Denon in for repairs.\n\nThanks\n\nAttached image is of the greyed out option in the Denon set up screen, that makes less of a hum. Which selecting the choices that are changeable make a louder hum sound. It's still not that loud. But still noticable.