E30 help--hear RPM's in stereo system

[Dave Pollatsek]

The stereo in my '91 E30 picks up the alternator (i.e., you can hear a
RPM-proportional whine in the speakers; helpful for matching revs, but
mainly irritating)... the car came with an aftermarket amp and CD player;
the previous owner said something about needing to put a capacitor in the
amp's ground connection, but what was stranger was that he said the problem
started after he put in a new alternator (I think)...
That sounds kind of like a hack to me; does that imply that my whole
accesory bus has a huge whine in it? The AM reception seems pretty terrible
as well, I don't know if that's the issue. The whine is at constant volume
whenever the CD player is on, regardless of CD volume (this supports the
theory that it's in the amp)

Basically, my question is this a problem with the stereo setup, or is it a
more fundamental problem with alternator/voltage regulator/etc... putting a
capactor on the amp sounds like a symptomatic fix; but would I be just
masking the problem while my engine chip, OBC, lights, etc slowly fry or
something?
In my limited grasp of electronics, I thought that capacitors blocked DC,
but passed only AC, with high-frequency filtered based on
capacitance--wouldn't a DC-blocker be bad for a ground connection without a
resistor in parallel or something?

Thanks for any suggestions!
-Dave

[Darren Lambert]

Hi Dave

Fit a new Supressor to the Alternator. Chances are the alternator that was
removed had a supressor on, the new one dosent, therefore the radio system
whines.

Cheers

Darren

P.S. If you still get some whining, fit another supressor to the coil....
shouldnt need to do this on a BMW though.

"Dave Pollatsek" <phobN...@yaSPAMhoo.com> wrote in message
news:3a10e2ec$0$442$6536...@news.bitstream.net...

[Dave Pollatsek]

Thanks Darren, I'll try that.
-Dave

"Darren Lambert" <darren...@hotmail.com> wrote in message
news:974211162.27270.0...@news.demon.co.uk...

> Hi Dave
>
> Fit a new Supressor to the Alternator. Chances are the alternator that
was
> removed had a supressor on, the new one dosent, therefore the radio system
> whines.
>
> Cheers
>
> Darren
>
> P.S. If you still get some whining, fit another supressor to the coil....
> shouldnt need to do this on a BMW though.
>
>
> "Dave Pollatsek" <phobN...@yaSPAMhoo.com> wrote in message
> news:3a10e2ec$0$442$6536...@news.bitstream.net...

[Cordovero]

I fitted two suppressors: one to the battery in the trunk, and one to
the head unit. These helped only a bit, about half the time.

Read: http://users.erols.com/achassel/noise.html

Chances are the left and right channel wires are routed along with the
power cord, and you need to remove the trim and separate them.

If you figure something out, let me know. It's driving me CRAZY!!!!
I haven't removed the trim yet, because I'm afraid I won't get it back
on right.

Nadav

On Tue, 14 Nov 2000 14:12:42 -0000, "Darren Lambert"
<darren...@hotmail.com> wrotf:

>Hi Dave
>
>Fit a new Supressor to the Alternator. Chances are the alternator that was
>removed had a supressor on, the new one dosent, therefore the radio system
>whines.
>
>Cheers
>
>Darren
>
>P.S. If you still get some whining, fit another supressor to the coil....
>shouldnt need to do this on a BMW though.
>
>
>"Dave Pollatsek" <phobN...@yaSPAMhoo.com> wrote in message
>news:3a10e2ec$0$442$6536...@news.bitstream.net...

[Dave Pollatsek]

Yikes, that sounds like a pain in the proverbial...
Since I don't have a garage, heated or otherwise, I probably won't be doing
any non "necessary" operations until spring (Minnesota winters are bad for
exposed hands on bare metal)
I was always reluctant to upgrade my last car from casette to CD, just
because I had heard so many horror stories about stereo shops botching the
installation, but know I'm in the predicament of the previous owner having
installed it at unknown parts... I confess I don't even really understand
how my car is wired up... I'm assuming that the CD receiver is being only
used as a preamp, with RCA's going to the box in the trunk, but I'm
wondering if the power amp of the receiver is driving the front speakers,
unless there are speaker wires going back up from the rear... the "whine"
seems to come mainly from the rear of the car, regardless of volume/pan/fade
settings, so I'm thinking the front speakers may be powered off the
receiver, so I suppose I could just try to shut off the amp and run on
tinny, but hopefully-hum free front speakers until spring.
What makes this extra annoying is that I don't have the removal "key" for
the stereo--the prev owner said the stereo stores don't give out the keys
for "security", but it really sounds like they want to make sure people
can't do work on their stereos themselves...

I'm thinking that it shouldn't be a huge pain to buy some cheap RCA speaker
wires from Radio Shack, unplug the existing ones at both ends, and run the
wires through the cabin of the car, out the window into the power amp, and
see if that helps, before having to actually rip out the existing wiring.

I'll post if I actually discover something, rather than continuing to ramble
speculatively...

-Dave

"Cordovero" <Cord...@yahoo.com> wrote in message
news:3a19ac72...@nntp.stanford.edu...

> I fitted two suppressors: one to the battery in the trunk, and one to
> the head unit. These helped only a bit, about half the time.
>
> Read: http://users.erols.com/achassel/noise.html
>
> Chances are the left and right channel wires are routed along with the
> power cord, and you need to remove the trim and separate them.
>
> If you figure something out, let me know. It's driving me CRAZY!!!!
> I haven't removed the trim yet, because I'm afraid I won't get it back
> on right.
>
> Nadav
>
>
> On Tue, 14 Nov 2000 14:12:42 -0000, "Darren Lambert"
> <darren...@hotmail.com> wrotf:
>
> >Hi Dave
> >
> >Fit a new Supressor to the Alternator. Chances are the alternator that
was
> >removed had a supressor on, the new one dosent, therefore the radio
system
> >whines.
> >
> >Cheers
> >
> >Darren
> >
> >P.S. If you still get some whining, fit another supressor to the
coil....
> >shouldnt need to do this on a BMW though.
> >
> >
> >"Dave Pollatsek" <phobN...@yaSPAMhoo.com> wrote in message
> >news:3a10e2ec$0$442$6536...@news.bitstream.net...

[Dog-n-Hog]

One thing I did in the past with one of my "noisy"
systems was to rework the amp-end of the RCA connectors.

All off-the-shelf RCA cables have the shiend and ground terminals
tied together at both ends. This effectively creates a ground loop
in each cable.

Cut off the RCA connector on the amp-end of the cable. Install
a new RCA connector, but leave the shield disconected at the new
end. This allows the shield to "drain" to the receiver side.

End of story, no alternator whine.

Norm

Cordovero wrote:
>
> I fitted two suppressors: one to the battery in the trunk, and one to
> the head unit. These helped only a bit, about half the time.
>
> Read: http://users.erols.com/achassel/noise.html
>
> Chances are the left and right channel wires are routed along with the
> power cord, and you need to remove the trim and separate them.
>
> If you figure something out, let me know. It's driving me CRAZY!!!!
> I haven't removed the trim yet, because I'm afraid I won't get it back
> on right.
>
> Nadav
>
> On Tue, 14 Nov 2000 14:12:42 -0000, "Darren Lambert"
> <darren...@hotmail.com> wrotf:
>
> >Hi Dave
> >
> >Fit a new Supressor to the Alternator. Chances are the alternator that was
> >removed had a supressor on, the new one dosent, therefore the radio system
> >whines.
> >
> >Cheers
> >
> >Darren
> >
> >P.S. If you still get some whining, fit another supressor to the coil....
> >shouldnt need to do this on a BMW though.
> >
> >
> >"Dave Pollatsek" <phobN...@yaSPAMhoo.com> wrote in message
> >news:3a10e2ec$0$442$6536...@news.bitstream.net...

[Dave Pollatsek]

That sounds promising--we did something like that when setting up a
recording studio at my school--we were picking up tons of 60-cycle hum
(50-cycle to you europeans) in the mixing board.

"Dog-n-Hog" <wo...@neosoft.com> wrote in message
news:FDFD88A9E2799467.04C92711...@lp.airnews.net...

[Mirage]

First, you need to establish where it's coming from.

Disconnect any cables from Amp input (apart from power leads)
and listen, engine switched off. Problems ? It's your Amp.

All fine, start the engine.
Whining sound ? It is your alternator, work on supressing.
Sometimes, problem is bad ground. Check you negative lead
connection first. If connection is bad
you're modulating your Amplifier via power line.
Re-routing the positive lead makes no sense to
me, as it carries pure DC component, no AC, noise introducing
component is ever present.

If all still quiet, connect your RCA's to AMP side, and short
circuit them on open sides. Should be absolutely quiet. If not,
you might have cable problem. Maybe cheap cables with bad
shielding ? Finally, suggested method with ground-shield cut off
on one side of cables should work, however, make sure that your
AMP negative lead, and your CD player, share same wire, hence
you will have only one return ground loop. If that is the case, your
RCA cables should work perfect without chopping shield on one side,
if not, your problem is grounding of Amp & CD player.

To put a capacitor over battery.....hehe, without going into electronics, is
not worth even mentioning, as your battery is biggest capacitor you will
ever find.
And, if you go across with resistor, surely, it goes in paralel, being just
a load on battery.
Also, you can not fry a thing by action like that. Yes, capacitor impendance
(active resistrance)
depends on it's own value in Farads and frequency of signal (voltage) on
it's end.
In your case, it would just smooth out the "ripple" from your alternator,
but, as I mentioned before
your battery behaves like one BIG capacitor...

Rgds
Alex