Well there are some electrical shield devices and sticky sheets made, one comes from Percy audio I think, its fairly expensive, its a metal sheet that can be formed to fit around transformers, and the chassis panels etc...
This could knock out the rf noise, also cables and placement, I would move the phono amp away from everything possible temporary and see, also the ground plug or electrical ground in your socket could be creating noise. Its hard to pin down, because there are so many factors that you could be getting noise. Also if the outlet your hooked up to in the house is out of phase(hot swapped with the Neutral etc...) could cause issue, this could be reversed using a ground cheater and flipping your plug on the phono amp over to just check, then fix the outlet itself if this is a cause of noise.
If you have a Ground pin on your preamp, or phono amp try to lift it and see, also try connecting your tone arm wire with and without the ground wire and see. I have also taken an extra piece of wire and attached it to the phono amp ground and then touched other screws on the amp, preamp, cd player whatever to see if a better common ground could be found to eliminate more background noise, I have heard changes.
This could knock out the rf noise, also cables and placement, I would move the phono amp away from everything possible temporary and see, also the ground plug or electrical ground in your socket could be creating noise. Its hard to pin down, because there are so many factors that you could be getting noise. Also if the outlet your hooked up to in the house is out of phase(hot swapped with the Neutral etc...) could cause issue, this could be reversed using a ground cheater and flipping your plug on the phono amp over to just check, then fix the outlet itself if this is a cause of noise.
If you have a Ground pin on your preamp, or phono amp try to lift it and see, also try connecting your tone arm wire with and without the ground wire and see. I have also taken an extra piece of wire and attached it to the phono amp ground and then touched other screws on the amp, preamp, cd player whatever to see if a better common ground could be found to eliminate more background noise, I have heard changes.