dvsdev
+1y
Guy at work had the exact same problem changed his head unit from a Clarion to a Pioneer (to run his iPhone thru) and it started to pop whenever he moved the selector knob.
As it turns out the Rockford Fosgate amp was "only" earthed to the seatbelt bolt (sanded prior to fitment) and the first time he turned the Pioneer on it decided to earth itself through the head unit (or so the stereo shop guy says).
This cooked the RCA track and speaker track inside the headunit, frizzled the RCA's themselves and blew one of the channels inside the amp.
Sounds pretty far fetched if you ask me that all this happened due to a bad earth on the sub but who am I to argue.
The problem was fixed by servicing the 1 day old head unit, replacing all the cooked bits inside, new RCA's, new Monoblock amp and drilled a big hole in his floor, grinded the paint and fitted a big earth to the amp and the battery.
Lets just say it goes now, but it was a very expensive lesson on proper earthing of stereo gear.