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Noise problem -- finally found the source!

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  • Noise problem -- finally found the source!

    I've been troubleshooting a noise issue for the past couple of weeks..

    I finally have it figured out: If I power my PC from a separate power source, e.g. another car (which is not on)'s battery, then there is NO NOISE.

    This proves the noise is coming into my +12v lead on my PC's PSU.

    So the PSU gets the noise, and it's grounded to my PC case and so is my motherboard presumably, so the noise gets into my motherboard and sound card, and voila, into my amp, and out to my speakers.


    What do I do?

    A) Set up my car PC/audio system with a separate battery?

    B) Install an in-line 1F cap? (Would that even help?)

    C) Make a new PC case out of plastic? Would that work? I'm concerned because if the PSU gets the noise, it can still travel through the wires on my motherboard and could it then get into my sound card's output?

    WHAT SHOULD I DO? (What did you do if you had this problem, any why?)

    Thanks in advance,

  • #2
    was there noise off of your cars battery when the car was off?


    • #3
      The noise only begins after my doors are locked or my doors are already locked, it seems.

      - If I leave my doors unlocked, and turn my car to ACC (not on, and not start), then it will not make a noise until I lock my doors

      - If I turn my car on (not start), my alarm will lock my doors for me, and then the noise will start

      - If I start my car, the noise is present as well..

      So it could be related to my alarm/doorlocks, but how would I ever know/find out for sure?


      • #4
        You could try a noise filter (sometimes called a choke) on your +12V wire. These are cheap and easy to find at RadioShack or online.
        1.6GHz HP e-PC, 768MB RAM, 120GB WD HDD, Slim DVD-ROM, Onboard sound & video, 7" Lilliput, USB GPS Mouse, Audiovox FM Modulator, Vector 400 Watt Power Inverter, Windows XP Pro SP2, iGuidance 2, 15" Samsung LCD for the rear *Carputer not installed*


        • #5
          Originally posted by dodgetimes2
          You could try a noise filter (sometimes called a choke) on your +12V wire.
          Someone told me that if I put a 12vout capacitor, not a big one, but like 100uF or something, then it might act as a noise filter, because the noise would run off once the cap is charged (closed circuit => a short). What do you think about this?

          I will try to get a noise filter and see what happens before I disassemble my motherboard and attempt to fab one out of plastic..


          • #6
            First make sure it isn't the ground path. Temporarily ground the PS directly to the battery using a long wire. If that fixes the noise, you just need to find a cleaner ground point.

            If that doesn't do it, use the choke from RadioShack. It looks like a bunch of wire wrapped in a circle and it basically blocks AC current. I remember the days when you'd often need one on a head unit.
            2005 Subaru Legacy GT
            Status: 40% - starting install

            AMD Sempron 3100, Biostar K8NHA PRO mobo, 512 meg DDR, WD 200 gig SATA, Opus 150, Xenarc
            JBL GTi 6.5 fr, JBL 5.25 rr, (3) JBL 75x2 & 1 1200x1 amps, PA MOFO 12 sub


            • #7
              get this and use your optical out from your sound card
              i have one and i think antimatter also does i think this a great
              way to prevent outside noise from entering your sound system.



              • #8
                I think the DC-DC PSU I have already has a ferrite core/choke in it. It's a big plastic round cylinder near the plug..