Ferrite Ring filters bad for Interconnects?

All ferrite filters are not the same!! You can get ferrite filters that filter different frequencies of RFI and EMI. The cost is really inexpensive and it it worth a try. Do an Google search to locate US companies that specialize in ferrite filters.

Opus 88 has it right

Ostensibly, the purpose of ferrite filters is to "clean up" the sound (get rid of hash). In my experience, at least, they eliminate too much, i.e., part of the music's body, and with it, some of the enjoyment of listening.

In my experience, they do not make the difference of that of a truly shielded cable.