My system makes this thumping sound whenever it's turned on, turned off, or when switching radio stations or CD tracks. I can't figure out what's causing this, and it's really getting annoying. I have 2 amps, and only the sub thumps, no noise comes from the front speakers. I swapped the front speaker amp with the sub amp to see what would happen and it ended up causing the amp to go into protection mode instead of thumping. Anyone know what's causing this? My system specs can be seen in my sig. Thanks.

 

I had a similar prob. Did it sound like a helicopter and still make noise when the volume was all the way down? I had my amp and sub hooked up to the factory deck. When it was making the noise I unplugged the RCA cables and it stopped therefore the noise was coming from the head unit. If you find out the problem, let me know what was wrong, the information couldbe useful. T

 

My Tube thumps when I turn it on, but it's caused by a POS radioshack EQ I use as for its sub level control (Only 1 RCA out). I believe the reason mine does it is that there is a surge when the capacitors in the EQ charge, because once the EQ is on, if I shut off the car for a short period of time and restart, there is no thump. I just learned to live with it, but it doesnt happen when I switch stations or anything. I would assume your HU is to blame, check the ground. If that isnt it, I'd say deal with it, its probably more expensive to fix than the unit is worth.