Is my ground loop solution safe?

MyPetFly · 03-15-2008, 09:31 PM

Hi,

I have just installed my first car PC (bought through the Mp3car store) and I have problems with the classic alternator whine or ground loop issue.

I have checked and double checked that everything is grounded correctly (even measured the resistance with a mulitmeter) and I still can get rid of the ground loop. The loop is definitly between my car PC and the head unit as I can plug an ipod or laptop running off its own internal battery into the aux in on the head unit and there is no alternator whine.

Anyway, by trial and error I have come up with a solution that "almost" gets rid of the alternator whine . . . . but I'm not sure if it will blow up my car PC. If I ground the ground on the serial port or video RCA output on the rear of my car PC case to the chasis of the car the alternator whine "almost" totally disappears. The only time I can hear it is when I turn the headunit volume up to almost the max and even then it is only just noticable.

Does anyone know if I will damage my car PC by grounding the serial port to the chasis?

Thanks

Bugbyte · 03-15-2008, 11:18 PM

I don't think that will be a problem.

Punky · 03-16-2008, 01:06 AM

basically ur grounding out ur case. when i did that to mine i totally got rid of the noise.
However i bolted my case onto the car's chasis.

MyPetFly · 03-16-2008, 02:33 PM

Great. Thanks.

brucedog · 03-16-2008, 09:55 PM

Measure voltage and current on that wire you are using to ground the carpc point to the car chasis. If you see to much current or voltage, there could be possibility of damage to occur.

Also, when you make that ground connection, is there any:
>spark
>loud pop in audio
>disturbance in carpc operation

If not, you should be OK.

Now, car audio purists may tell you that inserting a ground loop isolator (GLI) between your carpc audio output and amplifier input will cause loss in audio clarity or quality...

But, I had a problem with hum whan I installed a better sound card in my carpc. So, I had to go to Radio Shack, and bought:
http://www.radioshack.com/product/in...entPage=search

It worked like a charm. There was not "a little noise" - there was NO noise!

...and my ears and the ears of trusted confidants couldn't hear any harm to audio quality.

That's my happy ending. Maybe it can be yours, too.

hithere · 03-17-2008, 08:40 AM

The fact that you can get rid of the noise almost entirely by grounding this or that output plug indicates, as Punky points out, that your case needs a ground (often, the outer conductor on these outputs is equivalent to a chassis ground, and is connected to the case in some way). Ground your case as well as you can before resorting to a ground loop isolator (these items can rob you of highs in the music by the type of filtering typically present).