If you wiring something into a stock radio like I did you dont have much choice. I wired up a ipod dock to the stock audi bose system using the cd changer audio in. It sounded great until I plugged in the charger for the ipod. That created a ground loop, I tried different grounds for the charger and it all gave the same noise. I put a PAC noise filter in between the ipod audio out and the changer audio in and it sounded great.