How does the amp know when to turn on or off then if there is no signal from the stock HU? Sounds like a HU would solve alot of problems hahah any used ones for sale?
you just need a trigger to turn it off. you could use a switch (i wouldn't use this because i could forget to turn it off) OR you can tap into your ignition or cigerette lighter wire so everytime you start your car, it will turn on also. but what mr. wildman said that is, it will cause a loud thump everytime you turn off your car or turn off your stereo. just a simple "BOOM". so what i would do is everytime i get out of the car, i would turn down the volume and turn off the engine.