Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!unmvax!ncar!cruff
From: cruff@ncar.ucar.edu (Craig Ruff)
Newsgroups: sci.electronics
Subject: Re: Define "GROUND" (& how to solve a "GROUND" loop prob)
Keywords: ground, loops, earth, ship, plane, audio
Message-ID: <3297@ncar.ucar.edu>
Date: 26 May 89 17:25:52 GMT
References: <3917@merlin.usc.edu>
Reply-To: cruff@handies.UCAR.EDU (Craig Ruff)
Distribution: na
Organization: Scientific Computing Division/NCAR, Boulder CO
Lines: 23

In article <3917@merlin.usc.edu> cyamamot@nunki.usc.edu (Cliff Yamamoto) writes:
>	Here's the weird problem.  I installed a stereo and amp in my car.
>The amp is installed and connected to the battery.  This scenario is with the
>engine running, amp powered up :
>When RCA's are disconnected from the amp, no noise.  When I connect the RCA's
>to the stereo AND power the stereo with a bench power supply, no noise & plays
>fine.  BUT by just merely connecting the car body ground ONLY to the ground of
>the stereo, I get all kinds of motor/ignition noise.

I've got this same problem.  Luckily, the level of the ignition noise is low.
I've done the usual, and replaced all noise condensors in the charging/ignition
circuits.  I don't have any spark noise, so I didn't have to bother with
the spark plug wires.  I even went so far as to use shielded speaker cable,
grounded at the power amp ground terminal.  I guess I'll have to continue
to make changes.  The next step will be to hook the stereo ground to the
power amp ground with a wire.  Currently they are grounded to to different
points on the frame.  For reference, my power amp is installed under the
driver seat, which is within 2 feet of the stereo.  If the amp were in,
say the trunk, would the noise be worse because of the greater distance?
-- 
Craig Ruff      	NCAR			cruff@ncar.ucar.edu
(303) 497-1211  	P.O. Box 3000
			Boulder, CO  80307