BaysideC4

I have an annoying whine coming from my speakers, it’s directly related to my engines RPM and stops when I shut my radio off. I have an Alpine stereo that is using the factory power and ground connectors (though they were spliced).
I had always assumed I needed a power filter, and recently installed one. I still have the same problem.

Has anyone experience anything like this? Does anyone know how to fix it?

Thanks in advance.

Bill Wagner

It's an intererence problem. Most of the time, this is caused by a bad ground allowing a signal to be "induced" into the supply of the cars. Depending on what type of interference it is, the type of filter you have may end up being useless. Interference can be common mode (interference exists on both the supply and return lines in the same phase), differential (interference exists primarilly on one line (usually the "hot" lead and terminates at ground), or a combination of both.

I would start by trying to secure all grounds to the radio, and then evaluate other grounds, particularly those that will change output as the engine revs (like the alternator and the spark system, to name a few).

Hope this helps,

BaysideC4

I checked the radio ground, no problem there. Yesterday I discovered that I get the same noise through the speakers when I have my rear defroster on and radio off.

So now that I know it has nothing to do with the radio, where do I start? Could it be that the speakers aren’t grounded properly?

Any guidance would be greatly appreciated.
Brad

Doug H

Usually cuased by having power wire or RCAs close to car's harness or too close to car's power wires.

I just picked up whine since they added new plug ends this week. Anyone have ideas ideas on that on. Nothing like a $ 10k system with a whine. I know it is not my wiring and all my cables are shielded and twisted. How would work in the engine compartment now cause interfence with the stereo?

Adrian

Now Doug, you have my book right?. Go to the section in chapter 8 or is it 4 cannot remember off hand. Might be both. It is called "Electrical Suppression". You will see that 1989 and 1990 models were NOT fitted with a suppressor system in the engine bay. However from model year 1991 onwards all 964s were.
The first thing you do is fit this suppressor if you have these whines. Also check the condition of every ground stud. The come loose and they also get corroded. The condition of the ground straps between engine and body and the negative lead on the battery are all potential causes.
Ciao,
Adrian
964C4

Robert Coats

The most common engine-speed related noise is AC-voltage alternator whine that enters the audio system by way of a ground loop. Do a google search on "ground loop" to learn all the ugly details.

To fix it, there are two ways to go:

(1) Consolidate all the grounds in every part of the audio system. When there is only one ground, there can be no ground loop. Make sure to use a single, short ground lead that is securely fastened to a bare metal part of the vehicle's body/frame.

(2) Install a ground loop isolator device into the audio cables between the head unit and the amplifer. A ground loop isolator is basically a set of coils, which only allow DC current to pass. Since the noise source is AC, it won't pass through. These are easy to install, with RCA connectors built right in. Here's the one I used:

Ground Loop Isolator @ Radio Shack

A few more thoughts...

-I spent a LOT of time trying to get method #1 to work in a medium-sized system and was never successful. Nothing I tried would totally isolate the noise...I could reduce it, but it was never totally gone.

-I spent $12 on method #2 and it worked the first time.

Some people claim ground loop isolators cripple the audio signal and hurt the sound. I can tell you from personal experience the only difference I could hear was the absence of noise. Of course, everybody has an opinion on what sounds "good" or "right" so actual results will vary.

Doug H

Got it. Just have not had chance to read through it. Thanks for giving me the chapter numbers. I scanned it briefly last night thinking you had probably addressed the issue.

I am mainly concerned because I did not have the whine until they replaced my plug ends this week.

Doug H

My issues with a ground loop isolater is potential degradation of SQ. Not to keen on the idea of pitching my $ 150.00 RCAs and replacing the same with a Radio Shack isolater using $ 5.00 cables. I agree that RCAs and etc. will not make an audible difference in most systems, but when you are using very high end gear, you will notice a drop in detail/imaging and maybe clarity. My experience in the past is if one spends time isolating the source of the whine (usually an RCA or power wire near vehicle's harness) one can easily resolve the issue.

Doug H

Isolated mine to a crossover of all things in the rear panel. Replaced the crossover and attentuated the tweeter and no more noise.

marc 1xx1

Bayside:

PM me, I have a inline AC suppressor like the one in the picture above. If you would like to try it we can try to arrange to meet.

marc

BaysideC4

Adrian,

I bought the book through Amazon, still haven’t received it yet. Do you have the part number for the suppressor?

Thanks,
Brad