Interesting find. When using the PSU cable extension included with the SM560, I get some serious coil whine on my Strix 2080 ti, but when I go direct from the wall to my PSU this seems to lessen significantly....any thoughts guys??
What PSU do you have? Do you have a UPS that you could plug the computer into instead of direct wall power? You could also try finding a replacement extension cable and seeing if that changes anything.