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Discussion Starter #1
:shrug: Help please. Now the owner is whining and I am getting a sore head and a dent in the wall.I can't figure out the Alt whine coming out the speakers?I've tested for bad ground its as good as if I run a wire to the back.tried a filter in the main power wire even put power and ground from another battery sitting next to the car.The system is a in dash mounted in the glove box then Fm modulated to a 12 disc changer in the trunk with a couple of amps and a sub.The car also has Pertronic's one guy says thats the problem? any and all HELP would be great Thanks and have a nice day
 

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I was told (and in my case it was true) that the RCA wires from the back of the receiver to the amps must NOT be run near each other. They can cross feed & cause this symptom.
John
 

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I would agree. Something is causing an interference somewhere between the radio and amp or the amp and the speakers. I've always made sure to get monster RCA cables or something just as good and made sure that there was nothing close by that would cause such an interference. I would just say you might use heavier RCA cables. Thats my 2 cents.
 

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Most of the time this is caused by poor quality RCA cables or a low quality amplifier. I would go buy a better set, run them over the top of the car from the radio to the amp to see if the noise is gone. If so, run them through the car away from power wires. If not, put them back in the box and take them back to the store.

I worked at a stereo store for years and this happens from time to time. There are several reasons it can happen. The radio and amp grounds were a good place to start.

Does the radio you are using have RCA preouts or did you use a line output converter to create RCA outputs from the speaker wires. If you used a LOC, they can normally cause engine noise (whine) unless you buy a good quality LOC.
 

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Ditto the comments about the amp's power cables down one side of the car - RCAs down the other side.

Make sure the ground cables for the two amps are at least as thick as their power cables and ground both of them to the same location. Make sure the ground cables contact bare metal (not paint).

Are the spark plug wires of decent quality?
 

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Discussion Starter #6
Thanks everybody to answer everybody good ford plug wirers.the grounds I've checked with ohm meter no resistance.No LOC used to be now are monster RCA cables.Regretfully yes all the wires I am running down the one rocker and will change that right away.Thanks again everybody
 

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That is probably it then. Never run power wires down the same side as your signal cables. Alternators actually put out a pulsed AC signal(rotating equipment cannot generate a pure DC output) that is filtered to try to minimize the pulse heights and get a decently stable DC voltage The constantly changing voltage output by the alternator(you have to put it on an o-scope to see it) will cause a pulsed magnetic field in the power wire when the amp is turned on. This magnetic field will in turn induce a voltage into the cables adjacent to it(in your case your signal cables) which will then be amplified by the amps leading to your speaker whine.

Also FM modulators can be bad for picking up RFI if the problem still occurs with the cd changer and not the deck.

Jafo
 

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Need more info.

Is the FM modulator and deck grounded in the same spot? Did you try a 12v filter in front of the deck? Have you pulled the FM modulator out of the system?

In the trunk, is the changer and amps grounded to the same spot? In a star pattern? Did you try using a ground loop isolator on the amps? Did you try running a wire from the deck ground to the rear with the amp grounds? (Some RCA cable's have an extra wire built in for this.)

Did you try a 12v power filter in front of the amps?

Do you hear the whine from both the sub and the interior speakers? If not have you tried switching the RCA's from one amp to another?

Also, how high have you set the gain on the amps? This is usually not the problem but can contribute.
 
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