Problems when installed a touch screen radio

Mazda Protege 5 2002
Just installed a touch double din JVC radio to my P5, wired a 5 channel amp to door speakers and a Bazooka sub, everything went right until I started and run de P5, sound went up and down, off and on, muffled sound, a mess, like if there is some sort of connection from the radio to the car running. Do the same using it without the amp.

Any guess??? I was thinking in run the power cables out of the OEM harness.
Sounds like a flaky ground. Check how the adapter was wired. You might need to run a ground wire from the radio to the chassis and from there to the amp. Leave +12 alone,