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

[Raymond H. Tomlinson]

Ah, the joys of aftermarket stereo install.  I second Kirby's advice,
and will add a few pointers:

1.  make sure your patch cables do not run next to your power lead or
along existing power sources.  IME, running the patch cords down the
center tunnel is the best bet.
2.  YMMV, but you get what you pay for in patch cables.  I make my own,
but buy very high quality, shielded-twisted-pair cable and connectors.
3.  Make sure your amps are not grounded to the chassis.  Install them
on a board, and mount the board to the chassis.
4.  Keep your grounds as short as possible.  I use a separate
distribution block for both power and ground.  Ground all your sources
to the block, then the shortes run to ground.  Clean the ground of any
factory undercoating, etc.  One of the best grounds in the trunk is the
rear bumper bracket bolt.  Buy a solid brass "screw-type" terminal, not
a "crimp" type.
5.  Depending on your wattage, run appropriate gauge power and ground,
and match ground and power (i.e., 4AWG power = 4AWG ground).
6.  Lose the factory harness power and run a direct lead off the lower
power supply under the dash.  Do the same for ground.
7.  Do not run your amp turn-on lead near your patch cables.

Good Luck.

Ray Tomlinson

>>> Kirby Smith <kirby.a.smith at verizon.net> 04/30/02 07:41AM >>>
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.

kirby

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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