When the laptop is plugged into the aux input of my Pioneer 9300 on battery power playing mp3s or movies or whatever, it sounds great and works just fine. But as soon as I plug it into the AC power i get this weird loudass interference. It probably has something to do with a ground or something, but dont know enough to pinpoint the problem.

Installed on of those inline RCA filter tings, made it worse.

Also I bought an AC convertor for a trip once and that did it as well as when plugged into a wall

 

TTT

 

try one of the auto/air adapters made by APC. its made for laptops so you shouldnt have any problems with it, other than it costing 80 bucks.