AC Noise filter an isolator is a type of AC filter and should of worked for you but i believe you hook that up to the speaker line it self filtering it out their. An AC Noise filter will hook up to your power inputs to your stereo so no AC at all is makeing it into your stereo. I see this problem sometimes in 2 way radio's in trucks and thats what we use to get the hum off, I've never seen this happen with a stereo but i also dont fix that kind of stuff to often. Any ways what you want is a "AC Noise filter" it will have 4 wires just like the isolator did, sorry i wasn't more discriptive before about what type but that isolator should of worked they are desined to only filter out stray voltage not audeo. hope i was help full, Steven M.
