After sending my Crown amp in to be fixed and finding out nothing was wrong with it, I have pinpointed the problem with my rig. I have a loud crackling sound that keeps coming from my rig. It sounds like a loose cable, but is not. Come to find out the noise is coming from my Eden Navigator preamp. When I tap on the pre, the noise eventually stops. Could a broken or bad tube be the problem? I have opened up the pre to search for any loose connections, and found none. I thought I read somewhere before that a bad tube will make this kind of noise. Anyone with some insight on this?