I looked at a photo of the Bellari and perhaps if you put the phono pre into a Faraday cage? Also probably need some A/C filtering for the last little bit if quieting.
Get a couple of Ferrite chokes and put them on the power line. (if it has a wall wart PS, put them on the umbilical from the wall wart to the Bellari.
Even an aluminum foil Faraday cage can tell you if it will help. Just use a medium size box and cover it completely with the foil, allow only the smallest holes for the cables. If it works, then you can figure out how to make a cage that allows the heat to escape and still do it's job. I am not certain if a wire screen will do the job. If so Copper screen made into a Faraday cage (box)would be best. But i am not sure if the screen mesh is fine enough to block radio frequencies?
Get a couple of Ferrite chokes and put them on the power line. (if it has a wall wart PS, put them on the umbilical from the wall wart to the Bellari.
Even an aluminum foil Faraday cage can tell you if it will help. Just use a medium size box and cover it completely with the foil, allow only the smallest holes for the cables. If it works, then you can figure out how to make a cage that allows the heat to escape and still do it's job. I am not certain if a wire screen will do the job. If so Copper screen made into a Faraday cage (box)would be best. But i am not sure if the screen mesh is fine enough to block radio frequencies?