car audio noise... check it

[j_dunavin]

ok so i have been working on this BMW for the past three days now, JL audio stealth boxes, boston pros, And a new RF t600-4 power amp. Decent set up but holy noise!!
I went through everything i could think of, and used every trick i knew of, i even replaced the amp with the same model...no luck. I finally called Rockford and he actually suggested to try a diffrent brand of amp. Lo and behold, i put in one of our JL 4300's and blamo...no noise!
Has anyone ever heard of anything like that before?? Crazy hu?

[envisionelec]

> ok so i have been working on this BMW for
> the past three days now, JL audio stealth
> boxes, boston pros, And a new RF t600-4
> power amp. Decent set up but holy noise!!
> I went through everything i could think of,
> and used every trick i knew of, i even
> replaced the amp with the same model...no
> luck. I finally called Rockford and he
> actually suggested to try a diffrent brand
> of amp. Lo and behold, i put in one of our
> JL 4300's and blamo...no noise!
> Has anyone ever heard of anything like that
> before?? Crazy hu?

Yes, but not from removing a Rockford amp. It's usually cased by a cheaper amp. Cheap amps reference their inputs directly to power supply secondary-side ground OR even chassis ground. In a good car amp, the inputs are referenced to themselves by using a quasi differential amplifier right after the RCA inputs. I have found (in my own designs) that this really depends on the car. BMW are among the most difficult to interface, so I congratulate you on your install prowess.

[j_dunavin]

sure now if i can only get rid of the noise in the wife's lincoln ls. It's all boston, except for the kenwood head unit, which is the only peice i have not changed out yet. i hope that i don'y have to change out the amp though... i really like the gt50.