Swaped amps, got engine noise.

Well , I know this is a SUPER discussed problem , the engine noise.(Alternator wining) The car came (bought it) with 2 amps , one for subs and one for speakers. They were some small JBL and I decided to change witha new 5 channels that will pull speakers and subs. As soon as I changed the amps , the engine noise came up. The only thing I changed was the amp , same RCA wires , same ground same wire location. Headunit is a Pioneer. Don't want to use a ground loop isolator as will cut from the sound quality. Any ideea why the engine noise came right after changing amp ? I had the same problem with this amp in my older car but there I solved the problem by using a noise filter on the Battery and AC wire of the headunit. On this car this trick does not work anymore. I am asking again this engine noise question as on all the other posts I found regarding engine noise ,nobody replied to say if they got rid of the engine noise and what worked for them. Thank you in advance for the tips.Damn cold here ...

jaxman, what brand amp did you put in? Sometimes a different amp doesn't have as good of noise-reduction circuitry. Also, if the new amp requires more power than the existing ground can handle that could create noise as well

Hi. Thank you for the reply. I had 2 amps before in the car (with same head unit) and there was no noise at all. I swaped the amps with a 5 channel 1200Watt amp and now I got the noise. I have re-grounded the headunit and installed a noise filster on the + but did not helped much. Today I pulled out the RCA for the sub output and 85-90% of the noise is gone , still a bit there but I can live without it , what I can't live without are the subs. (2x10"). I will try tomorrow to re-ground the amp and install a noise filter on the alternator. The car is a BMW 325TDS from 1995. But as I stated , the noise was not there with the other 2 amps. I will also try to adjust the gains of the sub input , that might also help. The "new" amp is a Viper 5 Channel , not made anymore. Had some noise problems with it before but solved them by installing noise filter on the + of the headunit.Damn cold here ...

It sounds like the amp doesn't have very good noise-protection/reduction circuitry, since you've had noise issues with it before. The ground probably won't fix it either. If taking out the sub RCA helps it could be noisy cables, but you've probably already checked that, and it didn't have the problem with the other amps. Your best bet is probably the noise filter on the alternator, good thinking there. Let me know how it turns out, I've had that issue before, but I just used a different amp.

One more thing I noticed. When I start the car (with or without RCA wires for the subwoofer) I can hear a "pop" noise in the speakers right after I start the car. Then if I put the sub RCA on the amp and put the key into the ignition point (without starting) I can hear a kind of whining in the amp , verry strong in the start and then going lower, it will all take 4 seconds or so... strange.Damn cold here ...