car speaker whine

[fkuk]

Hi

in my car i have a amplifier powering the door speakers
but the problem is somewhere in the system noise from the alternator gets picked up. Alternator whine

this makes the speakers play a high pitched noise which gets louder and the freqency picks up as you rev the engine

first thing i did was disconnect the amplifier and made the stereo back to stock
the whine disapeared.


So i got some sheilded phono jacks
and used them with the amplifier but the whine was back

now im thinking of using a RC circuit, a low pass fillter to stop the high pitched noise

first i need to get the frequency range but i need to buy a nee multimeter that does frequncy
im thinking of getting ut60e, i think.
From maplin

but what i want to know is where should i attach the RC circuit and how it should be wired

should it be before amplification or after

and the RC circuit
the capacitor which attaches to ground in theroy where should that be attached
ground of car or negative pin of speakers

thanks

also correct me if i got something wrong

 

[ronv]

Some other people may have some better ideas, but I would wonder about a power or ground loop problem. Can you get ground and power for the amp from the standard audio system or as close to it as possible? Is the case of the amp grounded to the car frame? Try it both ways.

 

[audioguru]

You do not want to filter the signals because then most of the high frequency audio will be gone.

 

[Menticol]

I had the same problem on a Peugeot 307, and yeah the filter is not a decent solution. Do not use the car wiring to feed your amplifier, it's shared with other car's electronic components. Connect the amplifier ground (-) to the car's body, under a rear seatbelt screw for example. Scrap a bit of the paint to improve the contact. Run a wire from the battery (+) to the amplifier.

 

[cr0sh]

I found several pages on this problem with this search:

alternator whine - Google Search

My best guess is that the amp you are using has the audio ground commonned with the chassis ground, and you are hearing alternator and/or plug noise from the ground side.

Here's an interesting project:

**broken link removed**

And here's some interesting links that may assist:

Noise Prevention
Licking Alternator Whine
Alternator Whine

Good luck!

 

[fkuk]

ive managed to reduce the amount of noise by alot
fist thing i did was rewire ground and 12V constant to the car audio capacitor

and change the dials to some random settings untill the noise is hardly noticeable

so result!

 

[fkuk]

also i want to say something to

audioguru and mikeml

you know 4-5 months back i asked a bucket load of questions for the LM3916

i managed to get the project finished in a box and exerything and presented it in college and all went well

i probbaly wouldnt ben able to do it as good as i did if i did not have your help