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Thread: Using a "real" microphone?

  1. #1

    Using a "real" microphone?

    Hi all,

    I'm working on a project which needs a microphone input. For prototyping, the tiny electret condenser that's recommended for Teensy worked fine, but now I need something with higher audio quality, better rejection, etc. I'm using Teensy 4.0 with the Audio Shield.

    I'm fully prepared to cannibalize a "real" microphone, and it seems like my options are as follows:

    - use an analog mic, then use an amplifier to bring it up to line level for Teensy's line in
    - use an analog mic, then use an ADC to translate it for i2s input
    - use a digital/USB mic, and somehow feed that into i2s

    Would anyone be able to point me in the right direction here? Surely I'm not the first to need a beefier microphone with Teensy, but I'm having trouble finding other threads on the topic. Any suggestions would be much appreciated!

  2. #2
    i think the easiest/cheapest/most convenient solution is also the most common signal chain in professional audio surroundings - get a preamp to push the mic output to line signal levels, your first option. make sure you pick a microphone that does not need 48v phantom power, ie. use a dynamic microphone.

    there are plenty of very cheap mic preamping circuits out there, so that shouldn't be an issue. for example the famous 5$ mic preamp.

    of course your second option works as well, but depening on the ADC you might still need pre-amping/attenuation to get the mic output in the right voltage range.
    third option sounds like an ugly bandaid workaround to me.

  3. #3
    Thank you! This is very helpful. I will look into that $5 preamp, seems like the way to go. I'm glad not to have to resort to that third option...

    Thanks again!

  4. #4
    Senior Member ETMoody3's Avatar
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    The chip in the "5$ preamp" is more like $7 but it's still a great circuit.

  5. #5
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    Been reading this thread, since I also plan to hook up a handheld dynamic mic (eg.Shure SM58 or similar).
    Why couldn't I just use the mic input on the audio board to connect it to?

  6. #6
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    You can, although noise may be a concern.

  7. #7
    Senior Member ETMoody3's Avatar
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    The mic input on the teensy audio shield is designed to allow easy use of common electret condenser capsules.

  8. #8
    Senior Member ETMoody3's Avatar
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    Click image for larger version. 

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    The mic input on the audio shield isn't just an audio input, there's a biasing source.

  9. #9
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    Quote Originally Posted by alex_vy View Post
    Been reading this thread, since I also plan to hook up a handheld dynamic mic (eg.Shure SM58 or similar).
    Why couldn't I just use the mic input on the audio board to connect it to?
    Definitely rather noisy, dynamic mics are low impedance and a good mic preamp is needed to get a good
    noise figure - otherwise there's little point moving to a professional microphone in the first place. And without
    a differential input the EMI/hum pickup would be an issue.

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