nickthesafe

Hi Folks, i hope you can help me out with this real irritating problem; I have a radio scanner installed in my vehicle with an extension speaker plugged into the rear 'extension speaker' socket. It works OK, if a little quiet. So I built a 7w amplifier and hooked it up to the same output of the radio using a loading resistor across the amp input. The amp works wonderfully except that it is picking up bad noise from the vehicles electronic systems. I've tried regulating the supply line, adding extra caps etc, altering the load.... To check the noise wasn't coming down the signal line i coupled the amp to a 12v gel battery and it runs without any noise at all. What do you think guys???.......