A couple weeks ago, I started to experience some weird issues with my system. The system comprised of my factory head unit, an Alpine MRP-F240 to power the front and rear speakers, and a Kenwood KAC 8105D to power my subs. My vehicle is a 2006 Saturn VUE.
The problem started when all of a sudden a couple weeks ago, I would turn the volume up on the head unit beyond low listening volume to a normal listening volume, the sound would start to crackle and the intensity of the crackling would increase as the volume turned up though the actual volume stayed the same (what was coming out of the speakers didn't actually get louder).
My gut thought was the factory head unit was becoming problematic since every so often it'd have issues reading CDs and the steering wheel controls didn't always operate correctly (ex: when I'd hit the volume-up button, it'd turn the volume down).
So, I replaced it with a Kenwood Excelon KDC-X597 deck. Upon installing it, the same thing happened, start putting out crackling sound, and then didn't put out any sound at all. After turning the gains up on the existing amps, it started to sound normal without anything crackling, which I thought was simply an effect of having a different deck with a different voltage output. However, not long after as I started to tune it to get the levels right, the crackling effect in the sound came back and now we're back to no sound.
Now seeing the problem with multiple head units, I think it's the amp, and replace the amp with a new Alpine MRP-F300. No sound, at all (with gains turned all the way up). The head unit and amps themselves are all getting power, but there's no sound output at all.
The system was installed when I first got my car back in 2006 and had stayed untouched for about 6 years until my sub amp showed signs of age (channel was cutting in and out). I swapped that out in early 2012 and it was fine ever since. Now, the problem that I described has manifested itself and I'm at a loss as to what could be going on.