# Alternator noise.......



## SentraFourplay (May 11, 2004)

I have searched and searched, and performed all of the things to do to get rid of this damn alternator noise. I regrounded the amps, re-ran my patch cables on the opposite side of the car as the positive, and everything...

I have a kenwood mp3 deck, 6 1/2 200w kenwoods in the front doors, 6x9 300watts in rear deck run off of a kenwood 320 watt four channel amp, and two xtant 10's run by a 2 way kenwood 1000 watt amp, then a power distributor, and ground distributor.

The only speakers that transmit the alternator noise are the 6x9's. I turned the gain all the way down and there is still a little noise, but it's still there. And, no matter where the gain is set if that amp is on Low Pass there is no more noise. But, the highs are where my 6x9's shine. I am out of ideas. Please help.


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## sr20dem0n (Mar 19, 2003)

If you unplug one or both of the rcas from the amp does it go away?
If the headunit and amp are off does it go away?
What about if the headunit is off but the amp is still on? (just run a short piece of wire from the +12V input to the remote input to manually turn it on)
If the sub amp is off does it go away? (just unplug the remote wire from it)


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## SentraFourplay (May 11, 2004)

1.no
2.yes
3.not sure
4.yes


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## sr20dem0n (Mar 19, 2003)

hmm, alright, so with the rcas unplugged it doesn't help, that right there eliminates everything before the amp, headunit, wiring interference, etc. Since it goes away with the amp off, that means it's not interference in the speaker wire itself (rare, but it does happen). Don't worry about #3, if the noise stays with the rcas unplugged then it's not the headunit, so doing that wouldn't help any. Then since the noise goes away when you turn off the sub amp, that brings it down to a grounding issue. I had the same thing with one of my older amps. Never had any problems until I added the sub amp, and as soon as I did I had a ton of noise in the rear speakers. Tried playing with the ground and it helped, but I never completely got rid of it until I just took out the amp and replaced it with a different one.

Are your amps grounded to the same spot? Is the paint sanded away? Where exactly are they grounded?


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## SentraFourplay (May 11, 2004)

Why does it go away when it is set on low pass then? Then, with the gain all the way down in HP it is not very noticeable, but I still notice it.

I have a 4 gauge ground wire that attached to the seatbelt bolt in the trunk. Paint sanded, and washerrs on each side. That runs to my ground distributor and then two smaller ground cables to each amp.

I bought the amp brand new, so I find it hard to beleive it is that, but it could be.


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## sr20dem0n (Mar 19, 2003)

Not really sure why it would go away when set to LP, noise problems can be really strange sometimes though

When I had my problem it was 100x worse when my amps had a common ground, when I separated them it got much better. It's something you could try, only problem is to try it you need to get new ring terminals and everything, and then if it gets worse you need to go back to how it is now but the wires might be too short to go into your distro, etc. It's up to you though, I mean it's worth a shot.


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## LethalAudio (Feb 12, 2003)

Go get a set of filtered RCAs from radio shack or circut city. I had the same problem and I did everything from rewiring the whole system to relocating my battery to the trunk and it didnt work, but the filtered RCAs did. Be sure to look for the onces with teh cylindrical filter on it, everyone tells me that the ones with the rectanguar box on it sucks for some reason. Not sure why though.


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## sr20dem0n (Mar 19, 2003)

the noise is still there when he unplugs the rcas, which means the rcas themselves are obviously not the problem since completely taking them out of the loop changes nothing


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## LethalAudio (Feb 12, 2003)

oh i missed that part.
be sure to try different grounds and have a volt meter on you to check how good the they are.
that is a strange one, i dont know anyone thats had alternator noise and not been able to fix it with a good filtered rca.


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## SentraFourplay (May 11, 2004)

I had the grounds running to each seat belt bolt at first before I got the distributor and the bigger ground cable

I am starting to think it is something internal in the amp.


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## wickedsr20 (Aug 8, 2002)

SentraFourplay said:


> Why does it go away when it is set on low pass then? Then, with the gain all the way down in HP it is not very noticeable, but I still notice it.


Here's your answer:
The high frequency of the alternator whine is filtered out along with the other high frequencies when the x-over is set to low pass. In high pass mode, it passes the high frequencies (noise included) and filters out the lows.

Try moving the sub amp away from the other amp if they're mounted close together and see if the noise lessens or goes away. Not sure what to recommend without seeing the install.


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