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Thread: Ground loop sound, how to fix?

  1. #1

    Ground loop sound, how to fix?

    Good day guys and gals,

    I'm using the teensy in an automotive environment. The sound recorded through the teensy is fine until i connect the teensy to the ground of the car.
    AGND is used on the audio line, and GND for the ground.

    Once both are connected i get alternator whine sound. Is there any trick I can use to minimize this?

  2. #2
    Hi donperryjm.

    Just to start:
    What Teensy model are you using?
    Are you using a USB car charger to power the Teensy?
    If not, are you using a linear regulator or a switching power supply? What part/model?
    From where do you get the positive?
    What do you use to record and play the sound? Paul's Teensy audio shield? DAC on capable Teensy? Another way?
    How do you record the sound if Teensy it's not plugged to ground?
    How do you know the sound recorded is fine and the problem it's not there?

    As you see you are missing almost any useful information needed to diagnose the issue, and that questions are really basic.
    The less details you give, the less chances that you get a useful response because there is no enough data.

  3. #3
    Quote Originally Posted by donperryjm View Post
    Once both are connected i get alternator whine sound. Is there any trick I can use to minimize this?

    It sounds as though you have two ground connections. One for input power and another with your signal. The problem being that both are connected to the vehicle body. Creating a nice big loop to couple magnetic fields into. The usual solution is to eliminate the loop by having exactly one ground connection.

  4. #4
    That's what I did and it works OK now.

  5. #5
    Was wondering if i could join AGND and GND.

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