# Common ground fixed my alternator whine...



## lunchmoney (Dec 27, 2007)

*(Yes, I realize that there are already a couple of threads that I started on this topic, but they are weeks old, very long, and scattered... and since alternator whine is such a common problem, I thought it would be a worthwhile contribution to the forum to recap my experience in a concise post... if this disclaimer isn't good enough for you, well... you'll get over it... please don't turn this thread into another ***** fest... I really want this thread to be helpful to the countless people who have gone through this same headache with alternator whine)*

First, to recap the problem... I was getting a slight alternator whine... you couldn't hear it when music was playing, but unfortunately with my car the stereo is always on when the car is on (stock head unit), so if you weren't playing music you heard it... and it was annoying enough to warrant doing something about it.
*
Here's the setup:*

- Stock Mazda 6 Bose Head Unit with preamp outs, power and ground to the HU were "as stock"

- 5 channel infinity amp, 4 channels bridged in to 2 (120w x 2), 5th channel powering a single sub (300w). 4 gauge power cable directly to the battery. Grounded to the chassis just behind the rear seats with a 3 foot long 4 gauge cable.

- Phoenix Gold RSD 6.5's running passive in the front doors.

- Single 12" JL sub in a sealed box in the trunk

- RCA's run on the opposite side of the car from +12

My initial solution was to use a Radio Shack Ground Loop Isolator, which completely got rid of the whine... but I wasn't satisfied with it as a solution because *A.* it muffled the highs ever so slightly and *B.* it just went up my ass sideways that I had to resort to it as a solution.
*
So here's what I tried, that didn't fix the problem:*

- I tried grounding the amp directly to the battery... this was easy, just used a jumper cable outside of the car... nothin'...

- Tried muting plugs in the amp... this did get rid of the whine, and let me know that most likely it was coming from upstream of the amp, so it was helpful... but I already more or less knew that, since the GLI got rid of the noise... of course the whine was still there once I plugged the signal RCA's back in, so onward...

- Tried a better shielded RCA cable to replace my ghetto home-made-from-Radio-Shack-bits cable... nothin'...

- Ran the new RCA's through a couple of different paths to see if maybe it was picking something up... even ran it over the seats, so that it wasn't anywhere near any other wires, or even the chassis... nothin'...

- Grounded the head unit directly to the battery... nothin'...

- Tried pulling the head unit out of the dash, in case the HU's chassis was in contact with the car's chassis... nothin'...

**********************************************

*The Solution:*

SO... still thinking that there was a good chance that the head unit was the culprit, *this morning I tried grounding the head unit to the same place where the amp is grounded (on the chassis)*... 
*
BINGO!!!... the alternator whine is 99% gone*... you can still just barely hear it if the car is idling, and you rev the engine... but once the car is moving, you absolutely can't hear it... the slightest road noise drowns it out.

So my alt whine is gone, and I don't have to use the ground loop isolator any more... not using the GLI made my tweeters sound a tiny bit less muffled, a smidge brighter (in a good way), and a bit more free and airy sounding, if that makes any sense...

Psyched that this is FINALLY resolved... thanks to everyone here who helped me out.


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## spag_bace (Aug 24, 2006)

congratz!!!!


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## tyroneshoes (Mar 21, 2006)

You want to know what fixed my alt whine problem

http://www.crutchfield.com/App/Product/Item/Main.aspx?g=181150&i=003S15A&search=noise+filter&tp=2653

and it didnt run inline with the signal like a rca ground loop isolator


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## Turborusty (Aug 7, 2007)

What abut grounding to the alternator's case? This seems like ti could remedy a bunch of interference issues.



Turborusty


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## lunchmoney (Dec 27, 2007)

tyroneshoes said:


> You want to know what fixed my alt whine problem
> 
> http://www.crutchfield.com/App/Product/Item/Main.aspx?g=181150&i=003S15A&search=noise+filter&tp=2653
> 
> and it didnt run inline with the signal like a rca ground loop isolator


huh... never saw one of those...

actually, glad I never saw it... 'cause I probably would have installed one... I find it satisfying that I was able to eliminate the noise without any filters.


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## tyroneshoes (Mar 21, 2006)

lunchmoney said:


> huh... never saw one of those...
> 
> actually, glad I never saw it... 'cause I probably would have installed one... I find it satisfying that I was able to eliminate the noise without any filters.


I hear you when it comes to any filters that run inline with rcas. But when there's a ripple in the electrical current, or incompatible grounds, the filter comes in handy and doesnt degrade signal at all.


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## Lumadar (Sep 28, 2007)

Awesome, I posted about using a common ground in your topic!


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## Entityofme1 (Sep 15, 2005)

And I'm the guy who said the fella above had the right idea amongst all the other advice others were giving you......


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## grampi (Jun 29, 2007)

With every single install I did over the years in an American car I ended up with noise problems. I've done two installs now in Toyotas and have yet to have any noise problems. I wonder if there's any correlation there?


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## thapranksta (May 11, 2007)

I had noise problems before in a 'Yota so I would beg to differ.  Noise went away when I got a completely different amp.


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## Lumadar (Sep 28, 2007)

grampi said:


> With every single install I did over the years in an American car I ended up with noise problems. I've done two installs now in Toyotas and have yet to have any noise problems. I wonder if there's any correlation there?


Doubt it. My fords have all been noise free


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## AzGrower (May 30, 2005)

Lumadar said:


> Doubt it. My fords have all been noise free


As well as my Chevy truck....but thats expected as we all know that Chevy is a better built than any Phord...


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## Exalted512 (Jul 23, 2006)

AzGrower said:


> As well as my Chevy truck....but thats expected as we all know that Chevy is a better built than any Phord...


Very true. 
-Cody


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## Lumadar (Sep 28, 2007)

AzGrower said:


> As well as my Chevy truck....but thats expected as we all know that Chevy is a better built than any Phord...


haha, that's a giant can of worms. My good friend who JUST sold his Chevy truck would say otherwise though


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## Bluto Blutarsky (Apr 1, 2007)

grampi said:


> With every single install I did over the years in an American car I ended up with noise problems. I've done two installs now in Toyotas and have yet to have any noise problems. I wonder if there's any correlation there?


 Yes, it is because Domestic electricity is inferior to both European and Asian electricity.


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## lunchmoney (Dec 27, 2007)

tyroneshoes said:


> I hear you when it comes to any filters that run inline with rcas. But when there's a ripple in the electrical current, or incompatible grounds, the filter comes in handy and doesnt degrade signal at all.


Ya know what? I think I'll try one... I was driving around today, and I can still hear it... definitely a lot quieter than before, but still present enough to annoy me... I think I had a bit of placebo effect going on yesterday, thinking that I couldn't hear it at all... but I can... nonetheless, the common ground definitely got rid of most of it, glad I did it.


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## lunchmoney (Dec 27, 2007)

tyroneshoes said:


> I hear you when it comes to any filters that run inline with rcas. But when there's a ripple in the electrical current, or incompatible grounds, the filter comes in handy and doesnt degrade signal at all.


Just ordered one on ebay... for that cheap, what the hell, might as well try it... think I might be able to install it at the fuse box? (Mazda 6)


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## Yogi812many (2 mo ago)

lunchmoney said:


> Ya know what? I think I'll try one... I was driving around today, and I can still hear it... definitely a lot quieter than before, but still present enough to annoy me... I think I had a bit of placebo effect going on yesterday, thinking that I couldn't hear it at all... but I can... nonetheless, the common ground definitely got rid of most of it, glad I did it.


I keep going through the same problem! Thinking it’s gone just to hear it again 15 minutes later! Ugh!


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## Sounds_Insane (8 mo ago)

Yogi812many said:


> I keep going through the same problem! Thinking it’s gone just to hear it again 15 minutes later! Ugh!


Uh, *lunchmoney *hasn't been on the forum since 2012. This thread is 14 years old. Maybe look for a more current thread about engine noise, there are plenty.


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## 1nfinite (Apr 8, 2013)

have you tried grounding the RCA pre outs? Just my 2 cents, as had same issues in the past & sounds definitely like head unit.
Something like this.


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