Hi
Any suggestions to remove GSM interference from my 252? Happens with any source. Power down the 252/SupercapDR and it does away ie no interference comes through the 300 power amp.
I found this You Tube video that covers exactly what RFI I am getting - 800MHZ GSM buzz:
Any suggestions gratefully received!
Kevin
Where is it coming from? Not a lot of use of GSM these days.
I used to get GSM inference from a smart meter with my Lite when it sent my meter updates to the company that supplies my electricity and gas. I solved it by moving the Lite about a metre further away from the meter.
As David mentions, it would be good to identify the source of the interference. What other non Hi-Fi devices have you got sat near the system. Is it a continuous problem or intermittent ?
One other thing, you seem to have a number of sources, so it may be worth making sure you have ground switches on the system in the correct position (you have a CDX2 so assuming this is connected, analogue out to the 252, the ND555 should be set as floating).
Surely one for the ‘Which wine are you drinking?’ thread. 
Strictly speaking GSM is the standard also referred to as 2G, whereas most mobile phones are now using 3G, 4G or 5G, but it’s still sometimes used as a generic term for all of these. I’m sure everyone here knows what you are referring to!
As you have a turntable I would guess that this input is most likely to pick up the offending noise due to its sensitivity. As a test, does the interference stop if you unplug the Superline at the 252 input? That’s not a solution of course, but it might be a useful first step in narrowing down the problem. It’s possible that moving it, or its cables, might help, or there may be a different cable that would be less prone to picking up the interference.