An addendum to my post - Of course I neglected to include the power transmission lines which are of course unshielded.
They too will be subjected to bombardment of RFI -But only during the day.
A slant on RFI
The sun is 93 million miles away and it radiates among other things RFI.
There is no barrier to this Radio Frequency other than the earths atmosphere and a 1/4 inch glass window, behind which my HIFI rig sits.
Today I was playing a stream from Qobuz and had a call on my mobile. So I paused the stream.
It was a long call and during this time the sun had gone below the horizon.
I resumed the stream and was immediately aware of an improvement in SQ. More bite , more clarity -All the usual improvements we expect when having an upgrade.
I have , as many have noticed difference between night and day listening , often attributed to less "busy" power supply.
What I experienced was like night and day , but I can't quantify it , it is purely subjective.