Geez, this complicates by the minute, LOL.
That's why I was saying using a conditioner to filter local RFI. This local RFI may also come from the transformer itself (it was not designed with high-end audio in mind, so it may definitely release some operating buzz.)
In any event, I know the system will sound good plugged to the wall, but then you know it can improve. Steve underlines the 2:00 a.m. relatively cleaner AC for out of body listening experiences ... Simply put, end sound quality also depends on AC quality.
I just hope I can find a line enhancer that may do the trick ... As for the power cords, these may impart character or signature, but if they are well built, that's tantamount to room reflections or other sound affecting variables we'll never control totally.
I think mains' AC specs inconsistencies (voltage and cycles) and RFI are really sound damaging ... not signatures. Now I'm afraid I may need shielded power cords to shield the isolation T's own RFI emissions.

Have a nice listening session, Lon