That's not uncommon. See the following thread, in which the problem was ultimately resolved by connecting a braided rf ground strap between preamp chassis and power conditioner ground, and between power amp chassis and power conditioner ground. Since your system does not have a power conditioner, a comparable connection would be to ac safety ground (e.g., a screw on a power strip or wall outlet). Many other things were tried and suggested as well, some of which may work for you, including different connections of the rf braid.
http://forum.audiogon.com/cgi-bin/fr.pl?htech&1230309974
I doubt that adding a line filter/conditioner will help, though, because the signals are most likely being picked up through the air, not through the power line.
Regards,
-- Al
http://forum.audiogon.com/cgi-bin/fr.pl?htech&1230309974
I doubt that adding a line filter/conditioner will help, though, because the signals are most likely being picked up through the air, not through the power line.
Regards,
-- Al