[s-cars] Ground loop problem in aftermarket stereo install question.

Kirby Smith kirby.a.smith at verizon.net
Tue Apr 30 08:41:14 EDT 2002

One avoids ground loops by grounding everything to the same place,
preferably the point with the lowest signal.  That point, in turn, is
then grounded to the chassis.  Such a system may not be possible
depending on how things are mounted and internally configured.  In any
case, given Audi wiring complexity, the power stuff returns should be
returned to the battery.  Use the chassis where needed, not returns on
lamps, etc.

The previous comments are general, and do not represent any specific
knowledge of known "don'ts" on our cars.


Tim Sexton wrote:
>   Hello All,
>     I have just installed an aftermarket stereo system in my 94 S4, and
> have what I think is a ground loop.  However, being new the the car
> stereo world, I am going to run it past some of you experts out there.
>  The system consists of:  1.  Blaupunkt Munchen head unit  2.  Kenwood
> KAC Q74 4 channel amp  3.  Blaupunkt CDC A08 changer  4.  Blaupunkt 5.25
> components, front doors  5.  Pioneer TSA6999 6x9 rear fills.
>     What occurs is,  with the engine off,  I can hear loud static and
> electric motor noise when the head unit is in CD mode.  When I change
> tracks on the CD, it sounds like you can hear the arm moving.  Also,
> there is less static, but still audible, when the head unit is in tuner
> or changer mode.
>     For the amp, I pulled 12v directly from the battery, and pulled it's
> ground from a tail light ground.  For the head unit, I pulled 12v from a
> wire in the previous harness, and pulled ground from a ground point
> under the dash.
>     Does this sound like symptoms of a ground loop?  How does one
> correct a gound loop?  What exactly causes a ground loop?
> In addition,  I had the exact same problem when I used the Munchen to
> power the factory Bose junk via the pre-amp outs.
> Thanks for any advice you can share.
> Tim Sexton
> 94 S4
> 87 5kcstq
> 86 4kcsq
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