Whenever I change channels on my radio or switch sources (CD->Tuner->Telephone) I hear a popping sound in my speakers. I didn't really pay much attention to it until tonight when I hooked up my sub to an external amp. Now I get a really heavy pop coming from the boot. Seems as if someone hits me from behind whenever I change to another radio station :shock: . Does anybody have an idea as to what may be causing this? The speakers are wired to the internal amp of my radio for the time being. Radio is a Pioneer 7400MP. I also hooked the wires fom my handsfree carkit (perm, acc, mass and mute) to the wiring going into the radio.