I have a single subwoofer hooked up to a Sony xplod 800 watt amp. When I turn the key the amp powers on and the sub plays perfectly fine until I turn the volume a little past 20 or so (never a specific number). The sub will cut off and the green power protection light will turn red..... I know the amp is not faulty because I wired the setup to my girlfriends Sony xplod amp and had the same results. My power connection at the battery is rock solid and all fuses are intact. replaced the rca, speaker, and remote wires and made sure all grounds are secure and immovable. my voltmeter reads 14.5 volts when the car is cranked. the gain and bass boost have no effect on protection mode. I am close to giving up, my last step is to go buy a new head unit (aftermarket one already installed), if that doesn't work I might just drive the damn car off a cliff. The only logical explanation I can think of is that my alternator is wearing out, but that seems unlikely since my amp in not that powerful. PLEASE HELP ME OUT, ANY ANSWERS WILL BE GREATLY APPRECIATED. 5 STARS TO THE BEST ANSWER. THANK YOU.