RFI can come through your windows and changing cables (or wrapping them) or tubes may do nothing. You might just try turning the amp 90 degrees to see if it changes anything (but it's unlikely)
I used to live in a location with bad RFI - different radio stations from each speaker! - and the way I ended up solving the problem was to locate the stereo in the part of the place that was below ground level (and no windows either) and have the speaker cables come up through the floor. It worked beatifully.
I used to live in a location with bad RFI - different radio stations from each speaker! - and the way I ended up solving the problem was to locate the stereo in the part of the place that was below ground level (and no windows either) and have the speaker cables come up through the floor. It worked beatifully.