I recently took apart my system(working) and then put it back together. But now when I turn it on it makes a machine gun thumping noise. I put my sub into my friends working system and it worked fine. Then my amp into his car, worked fine. I tried a new pair of rca's that my friend had in his car in mine and it didn't make a difference. My friend suggested maybe my pre-outs on my deck could be bad or some bad grounds. I am open for any suggestions. Thanks for time.

 

sounds like a grounding issue... make sure the ground is clean and tight
good luck