well my HU always used to make my subs pop when i switches from the radio to CD. And I decided to go tear my dash apart and snoop around at the wiring. I couldnt find anything wrong with it. Since my HU has 2 sets of preouts, switched them to see what it was like. Well, my problem is solved. I wonder if my preouts were bad or something?
Same problem my mate had. I re-wired his entire system and still the subs popped wen changing from radio to cd, and also between changing tracks on the cd. So i tried changing preout connection and it did the trick. It had 3 preouts and the sub preout was the problem.
That is the good thing about Pioneer HU's, it actually shuts the sub amp(s) down while the face plate flips and ejects the CD so there is no popping. Polo.