Yes, a common response to ground loops is to try different spots on a car's
chassis for your grounding point or to make sure the spot you are using is
free of paint or primer, just bare metal. This can work many times because
as I stated before, in a perfect world, all points on a car's chassis would
have the same negative potential because the chassis is so large (again,
larger than ANY gauge of wire).
But experience has told me that different spots on many car's DO INDEED hold
differing negative electrical potentials. So you can become very frustrated
by trying spot after spot, sanding away to be sure you are touching bare
metals. Again, I suspect the answer to the riddle lies in differing alloys
that automotive manufactures use throughout the car and of course, every
alloy conducts electricity a little different. In the old days, of course,
when the entire chassis was made of one kind of steel, it was probably a
safer bet that you wouldn't have ground loop problems (as long as the metal
you were using was bare of paint or primer).
Grounding everything to the same spot is ESSENTIALLY the same advice I gave
but let me caution you about that. Grounding everything to the same spot is
actually, in truth, what you would see if you looked at my system (I use
four amps, an outboard X-over and a 6 band 1/2 DIN EQ along with my Alpine
HU and I am happy to say I have not a whisper of alternator whine in my 1999
Subaru Forrester), and although it is true everything is grounded to the
same spot, the KEY is that I use large gauge cable to ground everything to
this spot. That's why I gave you the advice I did. You see, if I had
simply told you to ground everything to the same spot you may have used 16
gauge wire over, perhaps, a 10 foot distance to ground, let's say, your HU.
The problem with this is that when dealing with low voltages, a relatively
thin wire like 16 gauge would have produced some internal resistance,
especially over a distance greater than a few feet. So grounding everything
to the same place is great advice with the caveat that you use large gauge
cable, AT LEAST 8 gauge, 4 gauge is better. Again, it help to remember what
we are trying to accomplish, we want all grounds to measure EXACTLY the same
negative potential. Electricity will travel through the path of least
resistance. We want to create a conduit that makes nulling these potentials
easy, hence large gauge copper cables, NOT very thin copper RCA cables. If
you were to use 16 or 18 gauge cable to ground your components (even low
current users like processors or EQ's) to a single point, you might STILL
find a difference in negative potentials and, again, some of this difference
might find it's way over the RCA's, which you DO NOT want. Using large
gauge cable ensures this does not happen. Also, again remember that it
isn't critical that all your grounds be at some SPECIFIC negative potential,
just that THEY ARE ALL EXACTLY THE SAME. So grounding them to the same spot
isn't as important as simply connecting them all together. That's why I
made the point that you don't necessarily have to move all your grounds to a
central spot (unless that would make things easier), but what's important is
that you ADD large gauge cable to all your grounds and have them all connect
together to null out any differences in neg. voltage potentials.
As far as ground-loop isolators, someone on that site said sometimes they
work and sometimes they don't. My experience is that as long as it is,
indeed, a ground loop you are dealing with, they will erradicate the problem
100% of the time. If they don't, then you don't have a ground loop to start
with. I'm not an EE so I can't tell you EXACTLY how they work, but they DO
stop that voltage leak that travels across the RCA's and do it in a way that
does not effect the sound quality in the least (at least not to my ears and
I have done extensive A/B testing with one once). Frankly, although it is a
band-aid solution which I tend to shy away from when it comes to
installation, they work so damn well it's tempting to just go that route as
opposed to tearing your whole electrical system apart and having to buy
20-30 feet of 4 guage cable. I have used those for a couple of friends cars
I did the install on and in every case, they worked magnificently. Although
my sure fire fix has always worked for my installs, I use pretty good gear.
I have encoutered over the years some low-quality processors or EQ's that I
simply was unable to remove the alternator whine despite all my tricks.
Their grounds were just integrated somehow with the RCA's and it was simply
impossible to completely erradicate a ground loop problem. For these types
of situations, the ground-loop isolators worked like a charm. So it's
definately something you might want to consider, you can always buy one and
if it doesn't work you can always return it, like I said they go for only
$20 at Radio Shack. But liek I said, if it is a ground-loop, an islolator
WILL get rid of the problem with no sonic differences. They are very cool
devices and for many of my friends, the best $20 they ever spent, even
though they are sort of band-aids.
See ya,
MOSFET
"sustain" wrote in message
...
Excellent explanation. I will look for an automotive electrician
first, before going to a Ford dealer.
What about this discussion regarding stereo systems and electricals -
http://www.3.8mustang.com/forum/show....php?p=3993863
Says pretty much the same thing, but much harder to understand!
Thanks
Sustain
On May 27, 2:46 am, "MOSFET" wrote:
Geez dude, that was hard on my ears. I couldn't even tell WHAT the heck I
was hearing, it sounded like a loud roar. Whine? Huh? It seemed to be the
only sample there so I ASSUME I was listening to what you intended us to
hear but I could make out no "whine", unless you want to call that loud
roar
a whine.
[snip]....
This has ALWAYS fixed any ground-loop problem with any car I have ever
worked on. It is, for me anyway, been a sure fire fix. If that sounds like
a little too much hassle, however, Radio Shack and others sell ground-loop
isolators that connect between the RCA's and I know those always work well
and, as far as I can tell, do not effect the sound quality. They sell for
around $20 I think and are a quick and easy fix.
Anyway, hope this helps.
MOSFET
"sustain" wrote in message
...
Could This Whine Be Caused By a Ground Loop?
The link below is to an MP3 file lasting only a few seconds (158 kb).
http://www.zshare.net/audio/605114385f1fe180/
Thanks.