help with amp

[lilancer]

Hi i have a 2002 ford explorer xlt. i dont think it has a factory amp. I am trying to hook up a amd and sub to the factory radio with a line out converter. But when the truck is running i get a loud whine out of the sub. Tried hooking up a aftermarket stereo and boom the noise was gone. I tapped the lineout converter off the rear speakers behind the radio. any help please im goin nuts. Thank you

 

[TeamPwnageBrad]

sounds like a ground loop, youve probably just got a ****ty ground on the amp or head unit.

 

[jimbo74]

also line out convertors tagged onto the speaker level inputs are garbage, and probably the reason for the problem as well... an aftermarket headunit is a much better option