Quote:
Originally Posted by amagalla
Can you explain this?
Thanks
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THe alternator whine you hear is AC voltage making it's way into your amplifier via the +12V connection. The old method we used was to try 1 or any combination of three things.
First and foremost make sure your battery terminals are clean and tight, a good colection
Second tie a .47 capacitor from the +12V lead to ground. Theory is a capacitor passes AC voltage but blocks DC...the AC whine will be shorted to ground and reduced greatly
Third get a capacitor , Electrolytic rated above 30V and a value of 2000 to 10,000 Micro Farad (Mfd) and tie this to the AC line to filter out the spikes causing the whine.
Shielded wire, like Coax. Use the center conductor as your +12V source and tie it directly to the +12V of the battery, ground the shield so spurious RF cannot get into your +12V supply
There are further methods of using a inductor (choke) and other things.
For more info and ideas read this thread
Noise Suppression Guide - Noise Suppression Guide
How To - Car Stereo - In Pursuit of a Noise-Free System: The Ten Commandments of Noise Prevention
Alternator Whine in Car Audio
Car Audio Noise Troubleshooting