Filtering Power Noise

DouglasABaker · Post by **DouglasABaker** » Wed Oct 24, 2007 4:07 pm

Hi all,

After resolving my issue with feedback in my rca's, I have tracked down and am trying to fix a new issue: Power Line Noise.

The issue seems to be my factory nav system. For reference, it is a 2002 BMW 5 series.

The issue is that my nav system introduces a whine and some static into my stereo. I initially thought it was the voice nav interface, but the interference and whine are present even when the audio link between the 2 components is disconnected.

In fact, the only way to make the noise go away is to disconnect the power to the nav system.

2 questions:
1. How can I resolve this issue? No, I am not getting a new nav system :) I thought about power filters, but I'd need 40A and 80A versions and haven't seen them that big...
2. How do I diagnose which component(s) need a filter if that is a viable solution?

Thanks all!

Doug

solacedagony · Post by **solacedagony** » Wed Oct 24, 2007 4:21 pm

Noise coming from your speakers isn't from the power line being noisy. It's from your signal wires picking up noise or from having ground loops.

I would venture to guess that since your nav system is what's causing it, you should try a new ground or locate your nav ground to a common place with your other grounds.

You can also try ferrite noise rejectors on your signal wires.

DouglasABaker · Post by **DouglasABaker** » Wed Oct 24, 2007 10:04 pm

Hi SolaceDAgony -

I originally thought ground loop too, but the speaker wires themselves are all twisted pair, so it is unlikely that I am getting noise from the speaker wire.

I tried Ground Loop Isolators - no effect.

I'm no expert, so please take this as the question that it is: Can it still be a ground problem if I have the noise with no connections between the nav system and the audio system? Literally, the only connection between the 2 is that they are both installed in the same car, but the 2 systems are otherwise not electrically connected except through the power cable (and probably ground).

Thanks again for the help!

Doug

solacedagony · Post by **solacedagony** » Thu Oct 25, 2007 3:31 am

I wouldn't be as worried about the speaker wire inducing noise as the signal wire (RCAs). Are the RCAs going by/behind/around the nav system? I don't think twisted pair makes the speaker wire immune to noise anyway.

I really don't think anything inside the nav system will induce noise, which is why I would go back to the ground issue. Do any installers on here have any advice beyond that?

Can you post pictures of the ground for your nav system? Have you tried running the ground from your nav system straight to your battery or to the common ground for your audio system?

smoker · Post by **smoker** » Thu Oct 25, 2007 5:17 am

solacedagony, do you mean the ferrite chokes that clamp onto the wire itself? i think that would be a good place to start as well if the ground doesnt fix it.

DouglasABaker · Post by **DouglasABaker** » Thu Oct 25, 2007 6:02 am

Hi solacedagony,

Yes, the RCA's do go near the nav system, but the noise doesn't go away when I change the location of the nav or the RCA's. Obviously I can't move either of them more than a foot or so, but I would think that should be sufficient to make the noise go away. Both pieces are in the stock location.

It does seem like a logical theory that I will explore further, however, as the whine seems to begin when the nav is powered, but the buzzing only kicks in when the nav screen itself turns on.

On the ground issue, I can safely say I have no idea where the nav is presently grounded other than that it is at the stock location. I have not yet ripped my vehicle apart to find out where "stock" is.

I tried moving the ground and power for the tuner unit, but have not tried moving the power / ground for the nav, primarily since I don't have a pinout diagram to determine which pins are power/ground. I'll continue to explore...

I really appreciate your help and thoughts!

Doug

DouglasABaker · Post by **DouglasABaker** » Thu Oct 25, 2007 6:07 am

Hi smoker / solacedagony -
I have to admit I've never heard of ferrite chokes. I assume you mean toroidal ferrite clamps - but what do they do, and which wires would they go on? And where?

Thanks guys - really!!!

Doug

solacedagony · Post by **solacedagony** » Thu Oct 25, 2007 8:37 am

smoker wrote:solacedagony, do you mean the ferrite chokes that clamp onto the wire itself? i think that would be a good place to start as well if the ground doesnt fix it.

Yep, I was just reading a thread a couple months ago where a guy said he used a couple and cleared up pretty much all his noise issues.

That's the one Douglas. Try PartsExpress tho for some better pricing. Search for "ferrite" and go all the way down to the bottom of the page. There're a couple different sizes.

These go on your RCAs. However, I'm not sure how far these are going to go to fix your noise problem IF the problem is a ground problem and not a noise induction problem. But anything is worth a try when it comes to these complex issues.

fosgate3 · Post by **fosgate3** » Wed Oct 31, 2007 5:52 pm

I was curious if the ferrites helped any. I have a 2007 Saturn Ion3 and this has been the hardest system I've worked on in 20yrs. I am having noise issues everywhere and im really trying to get anything to help. So far, I've swapped head units, amps, rcas, grounds, power wires, rerouted everything, relocated everything, had the alternator checked... nothing has worked. I thought of using copper shielding tape but i dont know if that will help and even if I would have to put it on everything or not. These ferrites sound like they could help.

solacedagony · Post by **solacedagony** » Wed Oct 31, 2007 6:19 pm

Try the ferrites and try moving RCAs while playing to see if there is any change in noise. Have you tried running balanced or digital?