AR-SP16 distortion problem

I bought a AR sp-16 pre amp and the sound is grate till I hook up the record out or main 2 which I use to send the signal to another room. It then starts clipping the bass and making everything muffled. Any sugestions?
How long are your interconnects? There could be significant signal degradation associated with using 20-30' long interconnects, esp. if they are RCA, not balanced (XLRs).
21' kimber hero to the main amps. And about 50' to the subroom of rg6. When the sub room is unplugged everyting is fine when I pulg in the other room it causes distortion in the main amps.
I'd contact ARC and ask them. I've had similar experiences with a different model ARC but never care enuf to ask, I just don't use the second set of outputs.
They tink I am overloading the outputs I like the pre amp but I may have out grown it.
Those are VERY long cable runs. Did ARC know that? Also not sure about using such a long length of RG6 for a line level signal. Maybe one of our tech-heads will chime in. Sean???