Odd Alternator Whine Problem?

blafrisch · 09-30-2006, 02:18 PM

I do have alternator whine and it is bad... but I can get rid of it by unplugged one channel of the RCA cable.

First: my setup...
Cheap head unit with Aux In and 1 RCA output
Carputer with a Soundblaster USB MP3+ sound card (If anything else matters I'll list it)
Kenwood 4 channel amp
I run a 2 channel RCA cable to the amp with splitters on the L&R channels so it can be 4 channel
Everything shares a common ground (the battery itself) and is connected to it with 6 gauge wire.

Second: stuff I've tried...
1) If I totally unplug 1 channel: no whine
2) If I unplug Front-Left and Rear-Right (or their opposites): no whine
3) If I unplug only one of the fronts: still whine in the read, none in front.
(Same goes for one in rear and both fronts plugged in)
4) If I plug the left channel in the Aux output and the right channel into anything else powered by the car: whine
5) If I plug the left channel in the Aux out and the right into something not powered by the car (MP3 player): no whine
6) Everything I've tried with aux output on the head unit I've also tried with the output on the USB soundcard with same result.
7) Running the RCA cables far away from each other and any power source has no effect.

I've tried a ground loop isolator also, but it is a Scoche POS. I say that only because if I plug that into the amp I get whine even when nothing else is hooked up to it.

1stclasso · 09-30-2006, 02:31 PM

2 things, either your HU RCA outs are bad,(inside grounding)

or u can try grounding a wire and putting the other end of it on the outer part of the RCA with them plugged in to the amp

blafrisch · 09-30-2006, 02:59 PM

It's not the HU RCA outs, cause I tried it with the out on the sound card itself.

I tried the second recommendation, doesn't help.

And to add to the list of things I've tried: Ive turned the gain down (and up) on the amp to see if it made a difference. Result: the whine is less but obviously the volume is also. It is more tolerable at the low gain though because the whine does not increase with volume of the HU or sound card.

blkwrx · 09-30-2006, 07:49 PM

http://power-factor-1st.com/shop/dc-...rd/sd-150.html

12vdc isolating dc-dc converter on the computer may solve your noise issue. The problem is its about $60-80 depending on the amps your computer is drawing.

ThunderStick · 09-30-2006, 08:36 PM

Do this and eliminate the wine for ever... By the way, I cant believe this is a new post. If you do a search, you will find tons and tons of info on this.
Anyway,
Get a high quality FM modulator. Will sound just as good if not better since there will be no whine, no interference from surounding wires and will make your install that much easier.
Trust me on this, I have tried many different things and the whine is allways there, maybe very minimally but allways there when tethered to your HU with RCA cables.
Wireless is the best way to go, do not get one that runs through your antenna or you will end up with the same problem.
You can pick up a goo done on ebay for about $30.00 it is worth the shot if you wanna give it a go.

blkwrx · 09-30-2006, 08:42 PM

FM mods have terrible audio quality. I'd rather solve the issue than put a band-aid on it. But to each there own.

blafrisch · 09-30-2006, 08:54 PM

I agree with blkwrx. I have had a wireless FM mod before and it was awful. There are simply too many radio stations to try and override and I travel from Raleigh, NC to Pittsburgh, PA fairly often so changing it often is definely unacceptable.

I may try to find a DC-to-DC coverter tomorrow when out shopping, mainly for the ease of returning it if I don't get the desired result.

One thing I have considered is selling my 4-channel amp and buying 2 identical 2-channel amps. One to drive the left, one to drive the right. While this is not my desired path, it may very well solve the problem and I'll consider it if nothing else works out.

As for this problem being posted all over the place, it is not. I could find no one with a similar description on this site or other audio forums with ease. I'm glad there are some people who are actually willing to help rather than saying why didn't you search, it's right there. </rant>

blkwrx · 09-30-2006, 10:24 PM

I mentioned the dc-dc isolated converters (make sure it has I/O isolation like the one in the link I posted) because I had a similar issue in my car. I was using the computers 5v power supply to power an mp3 player which went to the aux in of the HU. After getting a dc-dc isolated converter to convert the 12v to 5v and not going through the computers power supply the noise went away. I am not sure this will solve the issue but let us know I am very curious.

blafrisch · 09-30-2006, 10:44 PM

http://www.diysubwoofers.org/project...f/alternat.htm

This guy describes my problem and the solution to it exactly. Anyone know where to find an RCA cable with only one shield, but two conductors? I'm going to google for a while, but I figure I might get an answer here faster.

* EDIT *

I need about a 15ft cable

* EDIT 2 *

Would this do it:
http://www.procura.com/rhrca-15.html

I don't want to spend the $31 on a Monster cable unless I absolutely have to.

Shadow · 10-01-2006, 12:57 PM

Yeah, those would work. Get a little longer than you think you need though.

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