Suggestions for replacing an AV unit (5.1 surround sound)

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I've tweaked my PC system to be quiet. Unfortunately this has revealed that the ancient repurposed AV reciever (Onkyo TX-SR607) seems to have faint coil whine (I thought it was the PC and have spent days trying to track down the very faint low frequency hum and discover the source of the resonance). The sound is very low and with any ambient background noise it fades away, so it is possible I am just being too fussy. When quiet though, I can't un-hear it.

My setup for sound is HDMI (from an AMD RX 6700 XT with a dummy monitor) to AV Reciever to 5.1 speakers (Canton CX) as output. I'm seeking a replacement for the AV reciever. It only needs one HDMI as input, the usual decoders, 5.1 output. A full AV solution seems over-specified to me (although it might be the only solution), however, I'd like to use the existing AV speakers if possible.

I'm seeking suggestions :) It is entirely possible that faint coil whine is normal. I know very little about audio though, so this would be good to know.
 
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Is your computer and AV receiver plugged into the same mains extension? If so it could be a ground loop issue.
Seperate sockets. Thanks for the idea.

I've solved the hum now. While staring at the unit and some foam packing on the same shelf I thought to put the packing under the feet and the sound immediately went. I'd say silence is golden but for now I'm getting noise pollution from everyone else in the house. Now it is gone I can really appreciate just how irritating a barely percieved sound can be.
 
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Is this packing under feet of the amp? And if so what was the amp sitting on?
Yes. It was directly on a wooden shelf that I would describe as 'sturdy'. Its feet seem to only have nominal cushioning. Not something I'd thought to look at as it weighs a ton. I've previously taken it apart to clean it but never flipped it over. I'd bought silicon pads for all the speakers but it didn't occur to me that the amp might need them too. I listen at low volume so most people might not have noticed it.
 
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Yes. It was directly on a wooden shelf that I would describe as 'sturdy'. Its feet seem to only have nominal cushioning. Not something I'd thought to look at as it weighs a ton. I've previously taken it apart to clean it but never flipped it over. I'd bought silicon pads for all the speakers but it didn't occur to me that the amp might need them too. I listen at low volume so most people might not have noticed it.

I can only assume there was some grounding issue between the wood surface and the AV amp. Anyhow if it's worked it's worked.

As a side issue I have a 90's tape deck that started introducing background noise, I gently tapped the case and the noise stopped. I can only assume there is a dry joint on a printed circuit board. Are you sure it's the silicon pads, and not that you have moved something, or a dry joint the same as my tape deck?
 
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Are you sure it's the silicon pads, and not that you have moved something, or a dry joint the same as my tape deck?
Absolutely now after an experiment. Specifically the left hand side needs to be 'damped', however, I didn't like the jaunty pirate look so went for symmetry. For now I'm sticking with this as it works. If I was starting again I'd go with a simpler solution but as I had the kit spare I thought 'I can use that' and then dissapeared down a hi-fi rabbit hole for about two months. After getting it to work I'm extremely reluctant to abandon it and now the hum has gone it is back to the status quo. Incidentally the unit sits behind me and the PC in front, so I had extreme difficulty in locating the source of the almost subsonic sound. It was only by accident, when I powered up the AV first, before anyone else in the house was running interference, that I realised the source was not the PC.
 
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