Have to share with the community the final resolution of a frustrating effort to eliminate noise in my analog front end. For more than a year I had been struggling with a persistent issue of raspy low level hum and strange, seemingly random popcorn noise in my phono stage. I tried every combination of grounding approach between my equipment I could think of but beyond a certain point just couldn’t lower the noise floor further. Enough I told myself! I finally systematically unplugged every device regardless of what it was sharing the same AC circuit as my rack one by one and tested.
Viola! The culprits turned out to be two TP-Link powerline adapters I had been using for networking. I unplugged both and poof, beautiful silence from my phono stage. I use a Furman SPR 20i AC regenerator for power conditioning. It’s obvious these powerline adapters emit back on the AC circuit hash so intense it can get past heavy duty power conditioning. Both are now in the trash and I’m going hardwired point-to-point networking from now on. I can’t imagine how many of my other electronic components (e.g. video) were being assaulted by the noise these adapters produce.
Not sure how many of you have struggled with the same problem or how many of you are using powerline adapters, but if what I’ve discovered is any indication get those devices off your AC circuit!