Hi,

Jkohn is correct. A variable-speed resistor is basically like a continuous dimmer (for lights), used to vary motor speeds of fans. Many of them are totally unshielded and radiate all kinds of spurious interference. The Panamax might be of some help, but using a separate circuit to power the fan or your amplifier/receiver is the best option.

Regards,

Alan Lofft,
Axiom Resident Expert (Retired)