Audio Systems: Alternator Whine, alpine cda 9813, nissan xterra

Question
Hi,

I have a 2000 Nissan Xterra with the following car stereo setup:  Alpine CDA-9813 head unit, JL Audio 500/5 multi-channel amp, JL Audio StealthBox sub, JL separates in the front, BA 6X9s in the back.  When listening to something loud, no problem.  When listening to a quiet classical passage, or an audiobook, I can really hear a whine that matches the rpms of the motor.  At times it is downright grating, and I have to shut it off!  I get it regardless of the input source (CD, Radio, Aux like iPod).  I cannot really take it back to the place that installed the amp and subwoofer (this is when the noise started) as it is in another state, rather far away, so I am willing to tackle it on my own.  Where should I start? When I added the new head unit and speakers, there was no problem.  I have looked on a lot of forums, many point to faulty ground as a problem.  The RCA input wires and power wires are not run together, but It looks like the amp and head unit are not grounded to the same spot.  The RCAs are Rockford Fosgate, appear to be twisted type, which I am told is good(?).  Now what to do?  Help!

Mark


Answer
Mark,
Because the amp gets its main power directly from the main battery it will pick up noise/whine from the alternator. One way to solve the problem is to look at the alternator to see what the max amps output it has and stop by any good auto parts store or even a marine(boat)store and purchase a heavy duty noise filter that is rated at or above the amp rating of the alternator. Installing this filter as close to the output stud on the alternator should do the trick. FYI, basically an alternator will generate an AC voltage that will be rectified(converted) into a DC voltage/current. A small filter inside the alternator will filter out the left over component of the process of rectifing the AC to DC. Due to the excess heat in most engine compartments it can cause the filter to fail and then the whine will be heard in an amp set up. Lastly, a fast and cheap fix that you can try that I do on boats and cars with alternator whine is the stop by Radio Shack and purchase a few of those clamp on noise suppression ferrite filters and put several on each end on the power wires to the amp. You could also put a couple on the audio feeds into the amp to see if they help with the noise.



TOM,
T&D ELECTRONICS
tdeser@zoominternet.net