I have a 1994 audi 100 S, and i have replaced all my speakers and tweeters, and added 2 12's and 2 6*9's, the 12's are amped and so are the 6*9's. Everything is grounded perfectly and no signal cables are around power cables. When i turn it on it makes an anoying thump only from the amped speakers, the 12's and 6*9's have seperate amps, and they both pop. They also have a serious alternator whine, that ground loop iscolators will not even solve. I tried everthing imaginable :blink: . All amps are new including the headunit which is a pioneer 7600, and the amps are schoshe 550, and a pyle eternal 1400, i tryed all possible grounds. I grounded to battery which is under back seat, and i drilled numerous wholes to find the perfect ground, but all to no avail. i am very frustrated :angry: :angry: because with over two years of experiance and 12 american made vehicals with no problems, i am stumped as to what it could be. Please if anyone can help me i would really appreciate it. Thank you very very much.