I totally feel your pain! Glad you got yours to a relative minimum. That's where mine is at currently with movies/TV only, and if it remained that level when playing games, I'd have chalked it up to 'it is what it is.' Mine is also susceptible to any large power draw in the house. My girlfriend sleeps with a fan on at night, so on Saturday nights when she heads to bed (she works early early on Sunday), she flips the fan on and I hear a 'click, pop,' and the low level noise gets just a tad bit louder. It is a blower fan, since it moves more air for the dB level. It probably pulls more juice than a standard box fan, but it is the only way I can also sleep in the bedroom with the fan on. We had one go out, and I grabbed the big wire frame fan from the garage - big mistake. I had dreams I was in the back of a twin engine Cessna with a bunch of caged chickens and Short Round yelling, "OH NO DR. JONES!" Lol.The buzz during graphics intensive work happened no matter what, and my hdmi goes straight to the monitor -no audio, just vid only. Audio out was from the audio card, ditched that, now from the USB to a DAC. Didn't matter, buzz/noise continued. The whole system is susceptible to noise. When the landscaper came and was operating his leaf blower (gas engine) on the other side of the wall I have my equipment up against, I got interference through the speakers. The main system does not have this issue, it's definitely computer related. I do have a higher end nvidia card. Noisy buggers.
I just swapped from using two crowns (one for NHT's, one for the subs) to using powered monitors and one crown... same noise. Dropped a parasound pre-amp and went with a little digital pre-amp. Same noise. It's the computer and/or ground issue. The little bugger I linked made most noise go away but it's not ideal. Sigh. It works, and noise is very low right now, but the whole operation is frustrating. Best of luck.
It didn't work on my current system, but on my last system disabling some processor options in the bios killed the noise, it was power saving something or other. Oddly, putting power saving options back ON (instead of full performance 100% always/all/everything) in Windows 7 DID help with the noise on this one. Frustrating.
You know what - after resetting the bios to default the other night, that would have enabled the power saving features, but I didn't change my Windows Power Plan, so it is still not allowing things to throttle down to a lower power state. I should try enabling those again to see if I can get the level even lower for Movies/TV. Hmmmm, thanks for that, I wouldn't have considered changing those back after I initially set them to always on/100% to combat the initial ground loop problem. Since the ground loop is pretty nonexistent with the PS4, it might be just harming the noise with the PC on.
It took some jockeying of plugs in the 2 UPS units to get to a combination that didn't add noise to the initial ground loop issue, but I had that thought last weekend as well, and checked. Sure enough, the Marantz and PC were on different UPS units. So, at the risk of reintroducing the ground loop, I plugged them both into the same UPS. Thankfully, this did not bring back the ground loop, but it did not help the GFX card noise either. So I tried plugging the computer directly into the wall on the same circuit, which also didn't help the noise. Then I tried plugging the computer into a different circuit altogether by running a long 12GA extension cord. BAM, Ground Loop City! So I plugged the computer back into the UPS.I'm not an expert on this but I'm thinking it could be power related as well. When the GPU kicks in it starts using a lot of juice. Do you have the PC and the Marantz plugged into the same UPS? You might try eliminating the UPS and plugging the PC and the Marantz directly into the wall as well.
I have not however tried plugging both the computer and Marantz directly into the wall. I can definitely give that a try!
It is definitely when the GFX card is pulling a lot of power. Some suggested that running the PSU on the ragged edge with power draw might have something to do with it, but when this all started I was running a very nice OCZ (PC Power and Cooling Manufactured) 1000W PSU. I thought the PSU might be going out, and I wanted a smaller case anyway, so I downgraded the PSU to a 650W SFX (Small Form Factor) Seasonic so I could change my case to a Thermaltake G30, which requires a small form factor PSU. 650W should be plenty, considering TDP of the GTX1080 is 180W, and I am really only running the GFX card, SSD, CPU/CPU cooler pump, and (5) 120mm fans.
On a side note, something I have always wondered. I know S/PDIF only supports 6 audio channels, but why has no one explored running dual, or even triple S/PDIF for expansion of the number of channels supported? You could run 2 or 3 optical lines in a single jacket and output them with either 3 plugs or a triple combo plug. If 3 individual plugs, one could just run 3 separate cables or a combo cable. S/PDIF is cheap and on everything these days, and we have processors that handle gobs of discrete channels, so it really wouldn't be difficult or that expensive to implement. I know HDMI at 48Gbps (8k) can handle an insane amount of discrete channels, so it might be obsolete already, but optical noise rejection is always a desirable trait. But I've always wondered why consumer fiber based products have not become commonplace.