sidespar

installed new cd player (kenwood kc215s) in audi 90 quattro20V. when i dirve i get a whining noise coming out of the amplified back speakers that increases in pitch with rpms. I have tried everthing to get rid of it (tried different grounds all over the car - the best i could find was at the very front of the car). Obviously the problem here is a grounding loop. I need to re-grund the factory amps or i will probably put in a new amp and hook up some subs. What ca i do to get rid of the whining noise? Where are the factory amps located?

thanks

Chest Rockwell

Matt,

I had the same problem....tried different grounds..nothing worked. I fixed it by buying a noise reducer at Radio Shack. I'm sorry I can't recall what it's called, but it's like an active capacitor, as it has a power and ground lead. Solved the whine.

sidespar

Do you remember how you hooked the noise reducer up to the cd reciever?

Chest Rockwell

It's starting to come back to me now (this was 7 years ago). It hooks inline of the power and ground leads. Mine is hooked inline of my amp. I believe it's called a noise filter. It's not active as I thought, you simply run your 12v and ground into it, and then out to your deck or amp.

How do you like your 90 20v? I've been thinking about one lately.

Mancubus

I've had EXTENSIVE experience dealing with grounding problems in Car Stereos and while getting a noise filter will decrease the amount of audible whine, they also degrade your overall sound quality which in my opinion is not acceptable. Even with the best noise filters you will still hear some whine in quiet passages so your're really just applying a band-aid solution. Some of the things you should be aware of are :

1) When you are grounding your amps you should use the shortest length of cable possible.

2) When you ground the amp to the car body make sure that you sand the area where you are bolting the ground to make sure your ground wire does not come in contact with any paint. This may sound strange but most cars have metallic paint. If you ground to the car body on a car with metallic paint your ground is not isolated (as it should be) and you are in fact opening yourself up to a ground loop.

3)Your ground should be securely fastened to the surface of the car body.

4) Also, make sure your deck is properly grounded using the common ground that was provided by the guys in Germany. If you are using an external CD Changer controller, also make sure that it is connected to the common ground as that is another point of entry for alternator whine.

5) Another thing to consider as well is the connections to the CD changer. You want to make sure you use good quality composite (RCA) cables that will provide adequate sheilding from the other wires that it will cross from the front to the back of the car. Don't automaticaly assume that a good quality Home Audio RCA cable is adequate for Car Audio.

6) Another thing to consider, (which is a rule of thumb in the Car Audio industry), you should always run your power cable for your amp (as well as the remote wire) down one side of the car and your audio cables down the opposite side. The reason for this is obvious.

7) Check the connections on your speakers, if the -ve terminal on the speaker is touching the car body it too could cause a ground loop, introducing noise into the system.

8) Last but not least, try grounding the RCA's running from the deck to the Amps/CD Changers. You can do this by taking a 14gauge wire and wrapping it around the metal connector (not the core but the outside) and then connect it to the common ground at the deck. This is probably the easiest to implement and is usually the most effective so I'd start here.

If you feel queasy about trying the above, by all means go ahead and get the Noise reducer. IMO, it's not worth the trade off, but I'm an Audiophile with sensitive ears . They're not that expensive so give it a shot, if you don't like it you can try my suggestions. Good luck and let me know how it goes.

QCRAZY

..that all that got rid of the whine for me.

I tried noise filters on the power wires AND on the antenna. Nothing helped. The amps on these cars are built on the speakers....take a look. It has a very funny looking magnet?? It's actually the amp and I was unable to remove it from my speakers, I couldn't get the allen screw out!!

I replaced mine with some Kickers and after a little "gentle" persuasion they fit nicely. The hardest part was finding grilles to go over them Finally I did though and simply painted the grills to match. It looks like it came from the factory (unless you read the grills and see that it say "Kicker" on them). Getting new rear speakers would be my suggestion!!

Good Luck!!
---
Andrew
90 80Q
91 90
95 90Q

97A6guy

Radio Shack sells (sold?) an isolation transformer with RCA's on either end. I tested it for harmonic distortion, intermodulation distortion, signal to noise ratio, frequency response from 10Hz to 25Khz, cross-talk and phase shift. any change in signal could not be identified by the Audio Precision anylizer or by the HP equipment I used.

Mancubus

I don't recall the models I tried doing blind tests, (with the engine off so that Alternator whine levels were not a factor) but I consistently noticed a difference in Dynamic Range with the supressor installed. I opted not to go that route and I ended up finding the cause of alternator whine. I think a supressor should be used as a last ditch effort. It took me a while to track down the noise but now that I resolved the problem without comprimising SQ I'm much happier than if I 'settled'.

97A6guy

So we don't begin a flamefest, or (God help us) a Bush-Gore debate, I say YES, fix the problem if you can. If the weather is too cold to do it now, or time prohibits, use the isolation transformer. If you think it sounds worse, spend the time to fix it right.

I personally discovered that it is far better to let the pros do the install - shop around though. One installer wanted to charge $1000 to do what another charged $50 for - basicly a formed piece of wood that allowed my to use 6.5" speakers in my Buick. The Hafflers (they don't make car speakers anymore) that I used for the $50 install sounded much better than the BA's from the $1000 install. The price was about the same