Car charger + stereo cable to AUX == huge noise?

[Guest velis74]

So I had an Aux port installed in my Honda Accord 2007. The iPod variety, the other one didn't have stereo 3.5 jack.

If I plug stereo cable into my O2 and into the AUX port, I get a clean sound output if a bit low, but nothing that can't be fixed by cranking up the volume.

No problem here.

But the moment I also plug the cig lighter power into my O2, I get significant noise. So much in fact that certain songs are totally ruined by it. Ballads are out of the question. Metal works, but rock doesn't if there's a quieter transition.

The noise is constant with engine off.

With engine on I get myself a second rev gauge, even if it is "only" audio. Engine revs affect the noise considerably, both in strength and in frequency.

Yesterday I've been playing around with the cabling and found the following:

1. If I cut the cables between transformer (the part of car power plug which transforms from 12V to 5V) and O2 power plug, no noise

2. If I leave only the "-" cable ("+" is cut / not connected to the "transformer"), I still get noise

3. Installing a 100 pF capacitor directly after the alternator doesn't help in the slightest

4. Installing a 400 pF capactitor after the "transformer" doesn't help in the slightest

5. In fact - adding the capacitors worsened the situation.

6. Using a different car charger (original Samsung) doesn't help in the slightest

7. Plugging the power supply into another power plug doesn't help in the slightest

How can this be???

I really thought the capacitors would help, but they had no positive effect whatsoever. In fact they made things worse.

Did I use too small ones? I thought larger wones would just let the spikes pass them by.

But maybe the noise isn't a result of spikes? Maybe I should use a mF capacitor? Larger perhaps?

Anyone else had this problem and found a solution?

[Guest kdkinc]

only guesses,

Are your wires bundled to gather to look neat ? may cause a inductance type issue ?

Maybe to two power wires are acting like a antenna and catching and amplifying engine electrical noise (spark plug coil) or engine computer noise ??

#1 point in your post to me is the main clue to the issue.

hope it gives you some ideas

:P :(

Edited April 2, 2010 by kdkinc

[Guest velis74]

I don't know.

I don't see how #1 could explain much except for the fact that just plugging wires into O2's power / data plug doesn't create antenna effect..

By cutting the wires I simultaneously eliminate both inductive noise and noise generated by all prior components in the loop.

I find the fact that there is noise even then engine is off of most interest.

this reduces the possible culprits to car electronics and the car charger circuitry.

However I would dare to hope I eliminated the car charger circuitry by testing another charger.

Currently I still have both the induction and car electronics as the most plausible culprits.

I have also discussed the issue with a friend who says I will probably need a proper filter (with multiple capacitors + a coil). A capacitor just isn't enough for the type of noise a car generates (alternator + electronics). Even when I find one, placement will be of utmost importance. If the noise is capacitive, I will need to place the filter as close to the end of power cable as possible to eliminate the noise. If not, I can simply buy a good 12V --> 5V transformer with decent filter already built-in and place it between front seats where I currently have the existing charger.

Sorry, got lost in thinking possible solutions again.

Thanks for helping.

[Guest ad720]

You are creating a ground loop when you plug in the cigarette lighter power.

You need a ground loop lift (aka ground loop isolator).

http://www.amazon.com/PAC-SNI-1-Ground-Noi...r/dp/B0014KKZMI

[Guest kdkinc]

The outer day I was re-running my satellite radio wires in my truck.

I noticed that all the power wires have a coil of some sort near the ends of the wires.

Don't these coils prevent this issue? :P :(

:( B)

Edited April 2, 2010 by kdkinc

[Guest ad720]

The outer day I was re-running my satellite radio wires in my truck.

I noticed that all the power wires have a coil of some sort near the ends of the wires.

Don't these coils prevent this issue? :P :(

:( B)

That could be a ferrite core, which rejects RF or EMI interference. Not the same as a ground loop lift.

Edited April 2, 2010 by ad720

[Guest velis74]

You are creating a ground loop when you plug in the cigarette lighter power.

You need a ground loop lift (aka ground loop isolator).

http://www.amazon.com/PAC-SNI-1-Ground-Noi...r/dp/B0014KKZMI

Hm, this seems to be it. Thanks for the link.

Now I only have to find one here in Slovenia (otherwise I'll just be ordering a bunch of movies + games in addition to this device :P )

Possibly without cinch plugs. I only have pathetic two little wires after all :(

Thanks again.