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Thread: My mic input into the audio shield is super distorted/hot

  1. #1

    My mic input into the audio shield is super distorted/hot

    Hey guys,

    Iím using the audio shield and am getting major distortion/crazy high gain with electret mic audio entering via the ďAUDIO_INPUT_MICĒ
    input.
    Basically the mic signal is super hot, picking up things like my computer fan from across the room.

    Changing shield volume doesnít effect the distortion nor does changing the mixer levels of the signal coming in

    Is there perhaps a circuit I should be building for the electret mic prior to entering the mic input area? I just have the + and - leads connected directly into the mic input at the moment

    Thanks for any ideas!

  2. #2
    Senior Member oddson's Avatar
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    Your mic must have too hot a signal. A buffer amp with below unity gain might be needed.

    Make and model? (or better a link to the data sheet?)


    edit -- Are you sure the polarity is correct?
    Last edited by oddson; 04-30-2018 at 10:26 PM.

  3. #3
    Hey it's just a pretty basic mini electret:

    https://www.ebay.com/itm/20Pcs-Elect...72.m2749.l2649

    Product Name : Electret Microphone;

    Model : 6050

    Material : Metal;

    Sensitivity : 36-38dB

    Size(Not Included Pin) : 6 x 5mm / 0.24" x 0.2"(L*D);

    Frequency Response : 40Hz-13KHZ

  4. #4
    Hey so I had about 18 inch leads coming off the mic because of how it was situated in my device, and I tried just jamming the 2 legs of the mic straight into the GND and MIC inputs, and that seemed to solve the problem, no more distortion. The mic still is really hot though, and picks up the whole room pretty strongly, I'll look into building a little circuit before to reduce the gain

  5. #5
    Senior Member oddson's Avatar
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    The DAC chip has input gain settings in the audio object for line in and for the mic input.

    SGTL5000 chip audio ibject

    micGain(dB);

    When using the microphone input, set the amplifier gain. The input number is in decibels, from 0 to 63.
    You shouldn't need an extenal circuit. I've not used the mic input but hot seems wrong... are you very sure about polarity?

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