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Thread: Strange ground loop problem.

  1. #1
    Low Bitrate
    Join Date
    May 2006

    Strange ground loop problem.

    This has nothing to do with car computer at the moment, as I haven't rigged that up for audio yet.

    I have a headunit, with two phonos going to an amplifier in the back of the car.
    The amplifier is 2 channel, and powers my two rear speakers.
    It has a ground loop isolator at the amplifier end, as without it I get major interference/feedback when the engine is on.

    Today something has happened... For whatever reason the rear right speaker is very very quiet compared to the other speakers. I have checked the amp and headunit and all connectors seem fine. I swapped over the phonos into the amp to check it wasn't the speaker at fault, and the same effect happened on the left speaker instead this time (Speakers work fine).

    I took the ground loop isolator out, and hey presto sound is restored to all speakers! Problem is I get that interference if I turn on the engine.

    I tried another ground loop isolator as I had one spare thinking that was at fault - plugged it in, same problem again, one of the channels is very quiet.

    As it works fine without ground loop isolator it cant be a dodgy connector somewhere.

    Please say if you have any ideas?!!

  2. #2
    And then I was mod. Tidder's Avatar
    Join Date
    Sep 2003
    New Mexico, USA
    Screwed up isolator?

    Try RevFE
    The best resurrected frontend I've ever used, period.

  3. #3
    Low Bitrate
    Join Date
    May 2006
    Well I used a brand new one to test that and it had the same results.

  4. #4
    Join Date
    Jul 2001
    You shouldn't have to use a ground loop isolator. Are all of your components grounded to the same ground plane? In my car I try to ground everything to the floorpan because it's the biggest solid piece of metal in the car. The floorpan runs all the way from the firewall to the bumper in the rear.

    Also, have you upgraded your battery and engine ground?

  5. #5
    Low Bitrate
    Join Date
    May 2006
    I have a ground distribution block which grounds the amp (and PC when done) to the car chassis in the boot.

    The headunit is just stock ground in the ISO connector.

    I haven't upgraded the battery and engine ground, I tried to by buying some new gold battery terminals ( but it looked like it was going to be a lot of hassle doing the job.

    If you think it will make a lot of difference, I will look into it again.

  6. #6
    Join Date
    Jul 2001
    First, get rid of the ground block. Just put the terminals on the same bolt or screw. If that won't work out, then just put them close to eachother but don't extend any wires over 18". If they're all spread out, ground them as close to the component as possible.

    Your battery ground should be at least 4AWG. Find a bolt on your engine block and just get some setscrew type terminals or even better some Tsunami lok-nut or Stinger centerpin connectors and put one terminal on that bolt and another on your firewall if you can find a bolt there. If not, run it over to your battery.

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