[maemo-users] Audio connection problem

From: Chuck Robey chuckr at chuckr.org
Date: Fri Mar 14 20:21:41 EET 2008
Hash: SHA1

Mark wrote:
> On 3/13/08, Chuck Robey <chuckr at chuckr.org> wrote:
>> Yoiu original complaint didn;t seemo to list that you were charging at the
>>  same time,
> Because it's irrelevant; the noise is the same regardless of whether
> I'm charging or not, and I did say that it applied in non-automotive
> situations, which immediately rules out ground loop anyway.

If you were a reliable judge of noise, then you'd be right if it didn't get
better/worse when charging, but being in/out of a car hasn't the least to
do with it, noise from a charger system doesn't need to come from outside
itself (from the car) it can be self-generated by any switching power
supply, and they've gotten cheaper and cheaper, which means more and more
likely.  Someone commented that car stereos don't have this problem;
that;'s because those designers KNOW they must operate in that environment,
and reasonably (because anyone could tell if they didn't) they design for
quiet in such environments.  Sometimes, as in computer environments, it's
not always so that a key spec is audio level noise, so that can get thru.
Ask any engineer, what I'm saying is reasonable.

There are two reasons that you say (below) that the ground loop isolator
might help noise, and they're both equally likely.  One would indeed be
ground loop problems.  The other would be impedance mismatch problems.  You
might not care which fixes your problem, but if you jump at the easiest
guess, it's going to cost others who hit this problem (and rely upon your
assumtions) some woe, if their problem isn't fixed by such a solution, by
(for example) a ground-loop-isolation system that didn't incidentally fix
the impedance mismatch, something easily possible.

I can't tell you which is was, without further testing, but I CAN tell you,
from bitter experience, jumping to conclusions that aren't truly justified
can really burn the hell out of you.  Just don't want to spread FUD.  When
dealing with noise, it;'s ALWAYS a complicated subject, because there are
multiple sources that usually all contribute together.  Sometimes, fixing
the worst one is enough, but if you're a real stereo enthusiast, well, you
get my implication?

I'm pleased that your problem is fixed, though, and maybe that's sufficient
for you.

> By the way, I have yet to try a ground loop isolator that actually
> works. Some do reduce the problem, but they never eliminate it
> entirely. The bottom line is that the problem you're trying to solve
> with those is with the aftermarket component's poor design and cheap
> connstruction, which can't. be fixed with an external gadget. If it
> were actually the vehicle, then why is it that factory stereos _never_
> have that problem? There clearly is a design issue that the
> aftermarket engineers are ignoring.
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