@Cindyment
Thanks, and yes, either could impact sound, and neither is completely easy to 100% eliminate. All the power supplies and isolation i refer to are custom designed and built by me - as are some of the interfaces and clocks. So with luck, that's not the issue. I do believe i mentioned that isolation quality varies and I strongly prefer good transformers.
But what i experience is really not the issue. I am hoping to point to issues that many may experience, and why "cut and dry" technical answers give me pause. I have spent my career helping giant tech companies overcome technical sclerosis that is bred by engineers becoming comfortable with one paradigm or another - things they are invested and expert in.
I suspect that we have a difference in perspective. You seem very comfortable with what you can measure. I find Audio just full of the "unknown unknowns", things I can hear, but have difficulty measuring. This is nothing new - once (40 years ago) clocking and jitter was totally swept under the rug. My objective is to slowly learn what to measure, or at least what design concept correlate with good sound.
“if it measures good, and sounds bad, it is bad. If it sounds good, and measures bad, you’ve measured the wrong thing.” – Daniel Von Ricklinghausen, HH Scott to the Boston Audio Society, 1954