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Thread: ground loop or something else?

  1. #1
    Constant Bitrate
    Join Date
    May 2004
    Northridge CA

    Red face ground loop or something else?

    alright so this is my setup.
    i have a 7 inch touchscreen which is being powered through the cigarette lighter socket. the socket and plug are hidden behind the dash.

    first question would be that is the cigarette lighter a bad place to tap into power? ie the ground? im only using it for the screen but if you read on you will find out why im getting the screen involved in this.

    also im getting REALLY loud noise and buzz from my computer. im using the epia m10000 with the on board sound card. and it connects to a 300 watt powered eq.

    the eq has rca input so just for testing purposes i used a 1/8 to rca splitter to connect the computer to the EQ.

    after i connect the computer up there is no noise coming from the eq. however once i connect the VGA cable to the computer the noise comes out. its really bad and i can only minimize it by lowering all the eq levels to -10, i think its a 7 band eq, cant remember.

    i took out the vga and there is barely any noise. then i got the metal part of the monitor side vga connector and touched it on the metal part of the ocmputer vga port and it made the same noise. so another question, is the metal part of the vga plugs a source of ground or what not?

    i havent tried plugging in the vga withouth the screen plugged into the cigarette socket. it just dawned on me after reading a few things tha ti should try that.

    so im thinking the problem is either that the screen itself has the problem or that the cigarette socket is a bad place to ground/power the screen or anything from invovled with my carputer.

    any input or past experiences will be apreciated.

  2. #2
    Raw Wave Confused's Avatar
    Join Date
    Aug 2003
    Essex, England
    You want to ground EVERYTHING in your audio system to the same place.

    Amp, EQ, PC, screen etc.

    The cigarette lighter socket is generally not wired up particularly well, and could take a horrible route back to the battery, going through/past all manner of electrical "nasties".
    Co-Developer of A.I.M.E.E

  3. #3
    Constant Bitrate
    Join Date
    May 2004
    Northridge CA
    hmmm ic i need to try the grounding to the same place thing.
    also i forgot the mention that it does this without the computer powered or even hooked up to power.

  4. #4
    Constant Bitrate
    Join Date
    May 2004
    Northridge CA
    alright found out some stuff

    i tried the VGA connector and eq with my laptop. if i plug the laptop into the cigarette lighter the noise comes out. if i run the laptop offf battery power then its fine.
    so yea it was the cigarette lighter.
    seems like a bad place to ground

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