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Old 07-29-2014, 12:58 AM   #1
powpowpirateVT
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2002 wrx
blue

Default Stubborn alternator whine

So I've finally got around to attempting to rid my audio install of alternator whine, Iíve been at it for days and have made no progress. I installed the system a year or so ago and immediately got whine. Any advice on how to proceed would be much appreciated.

Right now the system is as follows.
CAR: 02 wrx sedan. 130k at install
HU: Kenwood mp445u (6 preouts)
HIGHS AMP: Eclipse ICE 4200 (4 channel)
LOWS AMP: Eclipse ICE 1200. DISCONNECTED
HU GRND: connected to ground clamp on highs amp
AMP GRND: Driver side rear seat belt bolt, COMPLETELY wire wheeled down to bare metal. Have tried other seat belt grounds as well as bolting the ground to the frame rail above the exhaust can. The length is about 10"
POWER: 4g run through firewall behind petals and down center of car into trunk.
RCA's: Run from head unit behind passenger side dash and down pass side of car. Right now I have a new set run outside of the car to test.



At the moment all unnecessary wiring is disconnected to troubleshoot, so far nothing here has worked. The head unit's power and ground is being run directly from the amp hook ups. RCA's are run outside the car. Amp remote is 'hot wired' to the power cable from battery. I also just upgraded the grounds under the hood including alternator (-) to intake manifold, intake manifold to battery (-), battery (-) to chassis (that super short ground wire next to battery), and also alternator (+) to battery, all jumpers are 4ga or larger. This improved nothing. I also have been testing with a separate coax speaker wired directly to the amplifier, so the speakers and crossovers are ruled out.

I've gone through every guide I could find and have not been able to resolve the issue.

some of this may be irrelevant but I want to be complete.
NOTES:
-Car on, not running PERFECT audio.
-Car running, high pitched alternator whine.
-Car running, HU on, amp off, no noise.
-Car running, HU off, amp on, same noise.
-I have swapped the head unit for a known good one, no improvement.
-I have swapped the amp for a known good one, no improvement.
-HU only connected to rca's, amp ground and amp power, noise.
-RCA's disconnected from HU and connected to amp. No noise.
-RCA's connected to HU and disconnected from amp. No noise
-Car running, HU outputting to an amplified home stereo via preouts, NO noise.
-Car running, ipod input directly to amps, NO noise.
-I have removed head unit and amp and installed directly to another car, directly to battery, I still get noise but there is significant improvement.
-I grounded the RCA shields to the HU frame, small improvement.
-I measured AC voltage across battery and (+) & (-) hook up on amp and I get 3mv, I believe this an acceptable amount of noise.

Interesting observations:
-With the car running, RCA's disconnected from the HU and connected to the amp if I touch a finger to the rca pin I get a crazy whine. It seems as though some how the noise is induced by power leaking through the head unit and into the center pin of the RCAs. I also have no improvement when I only connect the middle rca pin into the HU. Has anyone had any experience with anything similar? I've even brought this to an installer and they have no advice. I plan on trying out a power line filter tomorrow and will post results. Aside from that and ground loop isolators (in the mail) I have no clue what else to even test for.

Any help would be much appreciated.
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Old 07-29-2014, 02:26 AM   #2
djinn
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Default

What brand of wiring do you have?

Are your RCA cables shielded?

Are your wires run on different sides of the vehicle? (ie. power right side; rca/speaker wire left side)

Also what voltage is your preouts?

Low end decks usually have 2v preout vs higher end deck having 5v preouts


might have to do this.



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Old 07-29-2014, 03:02 AM   #3
powpowpirateVT
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I already grounded the head unit body to the RCA shields.

Not sure of the brand but the RCAs are shielded and older but of good quality. I have swapped in other brand new, known good RCAs with no luck so I'm pretty sure they're ruled out.

The power wire is no name brand but it's 4ga so should be sufficient. I have tried several ground wires in several locations including home depot 2ga thhn to no name 2ga braided audio power wire. Have also tried 4ga grounds.

Not sure of the pre out voltage but it is a highish end HU. I'm curious, why would the voltage matter?

Also, the whine intensifies as the gain is increased on the amplifier
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Old 07-29-2014, 01:08 PM   #4
LIChuck
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UGM

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There are two ways noise is introduced into a system, either radiated onto the wires (radiated susceptibility) or conducted (conducted susceptibility) through the power lines. All the shielding and grounding will not help eliminate noise that is conducted into the system. Based on your description, you have a conducted noise problem. The solution is to put a filter on the power lines as close to the head unit as possible.

A typical power filter is a series inductor with capacitors to ground, this is called a Pi filter. You should be able to buy a power filter from a quality audio supplier. If not, time to research Pi filters and build your own.
The ground in the picture above is not a good high frequency ground. You want to use low inductance wire (solid wire is good) and keep it as short as possible.
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Old 07-29-2014, 01:13 PM   #5
bobditts
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how long is the ground from your HU to the highs amp? have you tried using the stock grounding wire in the harness?
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Old 07-30-2014, 12:29 AM   #6
powpowpirateVT
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LiChuck. I did a ton of troubleshooting on it today and you're absolutly right. I went to walmart and bought a new amp, RCAs and head unit (I'm taking advantage of their awesome return policy) no change. Then I pulled the whole thing, screwed the HU and amp onto a board and rigged it up right next to my battery, MORE NOISE, and new noises from things like the dome light. I could be wrong but I'm pretty sure this means a poor chassis ground to battery creating a 'bottle neck' in the circuit. At this point replacing the RCAs with a ground look isolator yields noiseless perfect sound... FINALLY! this is curious since the same setup yields noise when wired into the trunk. Also I tried an audio transformer to filter the power and it did help a little. I'm going to order a purpose built one to see if that will help.

Yes I have tried the stock ground, problem is I'm pretty sure the car has a bad chassis ground somewhere that's making all the noise.

Thanks for the advice. I'll see what I can get done tomorrow.
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Old 07-30-2014, 12:31 AM   #7
TXwrxWagon
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Vehicle:
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WRB not so minty fresh

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#3: car running, HU off, still have noise through speakers..... Correct?

if my above statement is true I would want to know the following:

1. how are amps mounted to the car? VERY common "secondary ground plane" when amp heat sink is screwed directly to the car's sheet metal. Solution: Mdf board under the carpet, MDF glued to sheet metal, aboslutely no metal contact, and amp screwed to MDF.

My gut says you have an amp-ground plane issue.. I like Kenwood HU's but they are traditionally not well isolated. But that doesn't matter. You ahve done all the tests I would have and you deserve a beer and a pat on the back for trying it all befor posting.. well done!

Unscrew/bolt the amp from the car. Set it on something to totally isolate it from the chassis. Results?

2. Im going to share a wild/weird thing I experienced a few years back.

I had a combination of a bad battery and a loose/improperly grounded/tightened starter that was causing a low level noise problem AND Random electrical issues. Also, I've had an alternator (or 3-4) "test" ok with failing diodes. You are at a vehicle age where the Alt or Starter could be just "almost dead" to function, but are causing the audio issue.

Ground planes are wild.. I've had some things that make you go buy a case and think twice about the keg price, 4 days before a Regional Points event...

Good Luck..
~Rob
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Old 07-31-2014, 02:05 AM   #8
powpowpirateVT
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Progress! Replaced factory battery - > starter ground and battery - > chassis ground and the car LOVES it. I guess this has been a problem for a while because it runs better than it ever has. Audio wise... Everything is back in the trunk and no noise while using an isolator. Will put everything back together complelty tomorrow and try and get rid of that isolator. I'll write up everything I've been through to try and save some others from the hell that I've been through haha
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Old 07-31-2014, 06:00 AM   #9
bobditts
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The good ole "big 3" upgrade. Although you only did part of the 3, glad it worked out for you. Now just upgrade your alternator to battery cable, and you'll be even better.
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Old 08-03-2014, 12:47 AM   #10
powpowpirateVT
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blue

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I've actually created a new problem, after upgrading the grounds it now misfires until it's warm then it runs EXCELLENT. after changing everything back it does not fix the problem. Anyways, I started a new thread about that and I'll post back once it's solved.
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Old 08-07-2014, 10:07 PM   #11
anitr320
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WRB

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To fix mine I installed a line level booster and turned the gains way down. Completely got rid of it. I have a tablet install and I am using the JL audio complete volume control/line level booster and the hifonics 5 channel eq with built in line driver. I would try this because most line levels are .5-2 volts and when the amp tries to boost this signal it picks up alternator noise. The line driver is around 9v rms and this allows the amp to have an easier job. My gains are pretty much at zero.
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