I have a 640watt amp in my car and i've had it for about a year, just recently the speakers have been crackling, then all of a sudden i had no sound, i replaced the amp with a JBL 600 watt, wired it all in using me existing wiring kit, and nothing! checked the fuse from the main 12v from battery and it had melted. was a 10amp, i replaced it with a 10amp fuse and the speakers were again crackling, i then put in a 20amp fuse and it was fine, i then thought a 20amp was to much, so put a 15amp in, but now when i turn the stereo up the amp cuts out, then couple of mins later it will kick back in.

I've tried using a different earth, but the same happens.

Any ideas?

Thanks