Originally Posted by ncpl
Here are some results using an ENTECH device mentioned above:
I don’t think anyone is denying there is noise on a typical domestic ring main. The question is where filtering takes place. The point that Bob Stuart has made is that it takes place inside the speaker and before any power gets to the electronics in there.
So the question is: can this ENTECH device measure at that point? I think the answer is no.

ROON Rock on an NUC across the systems
Sitting room: 218, DSP7200SE
Study: 218, Quad 303, Spendor BC1
Bedroom: Musical Fidelity A3CR, Chartwell LS3/5a
Various Sonos boxes in bathroom and spare rooms