Re: [Tech - Audio] removing Alt whine

[Brett Van Sprewenburg <brett@netacc.net>]

>I was having this problem when I installed my amp.  Someone at 
>Crutchfield told me to ground the head unit to the same point where 
>the amp is grounded to.

This is the 'ground loop' problem I referred to in another post on this.
What can happen is that two 'ground' points in the car, can be at
slightly different 'ground' levels.  When two pieces of electronic equipment
are hooked together (with RCA inputs or otherwise), due to different
ground potentials, there's a small unwanted current flow directly to
ground.  This causes hum when amplified.

Here's something from a web site:

Ground loops occur when the ground potential between components differs in a
system. Symptoms of a ground loop may include alternator whine, and other clues
may be indicated by components shutting down when a ground is removed elsewhere
in the system. When in doubt about the identification of ground loops the best
approach is to measure resistance between battery ground and the ground
referenced at each component. A reading of 1 ohm or more indicates poor ground
potential. Always check resistance between battery ground and frame near the
negative battery connection to frame.


   Avoiding Ground Loops

        1.Make sure components are grounded to
	 bare metal surfaces, scrape paint with a
          flat blade screwdriver for 1/2" square.
          Check below before drilling.
        2.Use a star washer between the
          component ground lug and auto chassis.
        3.Coat connection with a
          corrosion-resistive preparation such as a
          light grease.

>
>Also, run the amp power line on the opposite side of the car as the 
>amp signal line.

Good advice, I've got to separate mine in an attempt to reduce noise.

>
>This should do the trick.
>
>Victor


==Brett

 \/  '84 Scirocco (ITB racer 2B) | "Hot VW's, take two home. They're small"
\/\/ '88 Scirocco 16v (Show), '92 Passat 16v (Winter+) | - brett@netacc.net

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