I had a Kenwood DDX7019 and just bought a Kenwood DNX9140. Everything was fine with the DDX7019 sound-wise but I wanted the GPS feature and the improved interface of the DNX9140. So I installed the the DNX9140, I started it up and it sounded fine. I then started the car engine and turned on the radio and there was a loud noise like a ground loop. I could hear a rumble and static noises and a whine noise that changed as the engine RPM's fluctuated. I have a PPI PC2100 as the front speaker amplifier and a PPI PC1400 as the subwoofer amplifier. Both amplifiers are located in the trunk area. I tried to run a ground wire from the head unit to the rear amps to see if it would solve the problem and it didn't work. The thing is I thought the subwoofer would be outputting all of this noise too but it doesn't seem to. Also the rear door speakers are connected to the DNX9140 headunit rear speaker outputs (internal amplifier) and there is no ground noise either.
So I don't know, should I just get a ground loop isolator? It's weird that this didn't happen with the other headunit even though the wiring was exactly the same (the wiring harnesses were even interchangeable and matched each other).
