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Thread: Ground loop issue - need some advice

  1. #1
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    Ground loop issue - need some advice

    Ok, after searching through the Car Audio forums and reading a lot of threads on ground loops and trouble shooting them, I have some questions.

    I have my carPC installed using a DSATX dc-dc converter. I am using a PCI audio card (SB Audigy 2 ZS) for the audio. From the PCI card I am using (2) 3.5mm phono plug to two male RCA connecter cables to go out to my front and rear amps (David Navone AMP-100).

    When I power the PC on (without the car running) I hear some aweful noises that I can only assume are coming from the HDD and other components from the PC. If I plug a set of headphones into the PC instead of going to the amps, I do not hear the noise. I then took an old Walkman and plugged it into the same phono-rca cables that go to the amps, and everything sounds fine (no noise). Therefore, I am pretty sure that the problem has something to do with the PCI card or the PC itself.

    I am using a distribution block for my power as well as a small one for my grounds. All of the grounds for the amps, PC, and a power relay for the PC are tied to the load side of the distribution block and the line side is tied to a bolt that has had the paint stripped off from underneath it using 8awg wire. I also tried to run an 8awg wire directly from the ground distribution block to the negative side of the battery, but that did not change anything. I also grounded my PC case (DIY homemade case) by grinding off some paint and using a ring terminal to go to the GND terminal of the DSATX. That also did not help the noise problem any.

    I picked up a Scosche Ground Loop Isolator (ES034) and hooked it in between the PC and front amp (through the RCA cable) and it got rid of the noise completly. I would rather not leave this in there as a permanant item since I see these as just a band-aid.

    What else can I do to eliminate the noise? Is it in fact a ground loop? Is it possibly coming through the sheild wire on the RCAs?

  2. #2
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    Anyone?

  3. #3
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    Quote Originally Posted by LYHTSPD View Post
    What else can I do to eliminate the noise?
    you can purchase a new head unit....


    That ground loop isolator is the cheapest way out.
    i have one, hidden away in my car and i forget it's there. Works wonderfully and i love it!

    you can also perfrom an upgrade to the "big 3" if u want...

  4. #4
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    Quote Originally Posted by trinybwoy View Post
    you can purchase a new head unit....


    That ground loop isolator is the cheapest way out.
    i have one, hidden away in my car and i forget it's there. Works wonderfully and i love it!

    you can also perfrom an upgrade to the "big 3" if u want...
    I have already done the "big 3" awhile back. I am not using a head unit, all the audio is coming from the pc (AM/FM included). The GLI just seems like a band-aid solution though, and I am not much into band aids.

  5. #5
    MySQL Error soundman98's Avatar
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    you could try grounding one of the rca negative leads-- in most cases, this gets rid of the noise.

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    Quote Originally Posted by soundman98 View Post
    you could try grounding one of the rca negative leads-- in most cases, this gets rid of the noise.
    Yes, this was also on my "to try" list. Does it matter which one I ground, or just ground both L & R to be safe?

    Thanks for the replies!

  7. #7
    MySQL Error soundman98's Avatar
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    Quote Originally Posted by LYHTSPD View Post
    Yes, this was also on my "to try" list. Does it matter which one I ground, or just ground both L & R to be safe?

    Thanks for the replies!
    you only need to ground one--the other rcas will ground through it. grounding 2 might induce a loop(again).

  8. #8
    Maximum Bitrate Woofnstuff's Avatar
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    only one of the audio out 3.5mm jacks on the sound card are normal headphone style, the other 2 are 3 output plugs.. look close at this

    so you would be in theory connecting positives to earth here



    might not be your exact card but thats the sort of plugs it has

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