Phoenix Gold Phorum

I'm fishing for a few ideas that you guys might come up with:

X200.4 has a continuous "fuzzy scratchy" noise coming from the right speaker only when I have the lowpass x-over select button "off." When I press it in (on) it goes away. This happens on the rear set of channels only.

I've double-checked my grounds and other connections and everything checks out okay. Do I have a damaged x-over?

Is it an engine whine type of sound? I'm not sure of the design of these amps, but I've delt w/a few installs from time to time that had that whine and when you use the lowpass it filters that sound out. My guess that's what's going on. Not the engine whine, but the lowpass is filtering out that scratchy fuzz.