Did you plug both cables into that same port? Make sure its not a short in the cable itself. I had a short in an RCA cable and it sounded as you describe a crackling sound.
Crackling noise
I finally have my basic system set up Krell Phantom, Krell 3 channel amp, and Rotel HD CD player, and SF evolution monitors. All of a sudden I have a low crackling noise and it happens only in one channel. It's present when I disconnect the CD inputs. Also it switches from L channel to R channel when I switch the XLR cable; it doesn't happen to both channels. I switched out for new fuses. Noise does go away when I turn off the power amp and leave the pre amp on, which should normally happen, right? Any ideas? I contacted KRell and they are out of the office. Just doing preliminary homework until Monday/Tuesday.