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
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.
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.
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: