I have got a 580W Pioneer amp fixed to the rear of the back seats in my Focus ST170. Its started playing up and i am getting alternator noise through my speakers, sounds like a supercharger. I have been told its a bad earth, so i rubbed a section of paint away and took it to bare matel under where the seat belt bolts and fixed the earth here. It was ok to start with but its gone back to producing alternator noise again after 6 months!! Checked all connections and everything seems ok.
The only thing it might be is where the power and earth connectors are soldered to the amp wiring board, it seems a bit loose there. Would this cause it? or is it nothing to do with the amp side of things. Im trying to establish the cause. It only does it when the amp is on
Thanks

 

What kind of cables did you use, high quality or just run of the mill stuff, also your not reccomended to run the power lead and RCA's down the same side of the car as each other as it may cause interference.

 

Sounds like the supressor on the alternator isn't working...

And rog is right on running power cables and audio cables separately.

 

Both of the above can cause it, cables and supressor, another thing you can do is connect a wire from your earth point for your amp to the neg on the battery, this often cancels it out, failing that a ground loop isolator would be next.
It tends to be a problem with either crap cables or cheaper amps normally.
tabetha