Electret condenser microphone

Discussion in 'General Electronics Chat' started by crobertsbmw, Sep 13, 2011.

  1. crobertsbmw

    Thread Starter New Member

    Sep 7, 2011
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    So I bought one of these microphone's off digi-key.
    http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&KeyWords=CMA-4544PF-W&x=0&y=0
    I don't know much about them at all. But I was thinking that if I sing into this thing I should at least be able to create some type of a voltage difference on the two leads. I have it hooked up directly to an o-scope and no matter how much audible noise I create I can't seem to get my o-scope to see any signal. What do I need to know about these microphone's in order to make them useful?
     
  2. bertus

    Administrator

    Apr 5, 2008
    17,381
    3,118
    Hello,

    Did you have a look at the datasheet?
    CMA-4544PF-W

    On page 2 there is a schematic.

    Bertus
     
  3. Veracohr

    Well-Known Member

    Jan 3, 2011
    611
    89
    It requires a DC voltage, check the datasheet.
     
  4. crobertsbmw

    Thread Starter New Member

    Sep 7, 2011
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    Now I just feel dumb. I did look at the data-sheet, that is my problem. I should try reading the entire datasheet before I post, then I won't miss things like schematics that are posted. Sometimes I just need someone to help hold my hand. You know what I mean.
     
  5. #12

    Expert

    Nov 30, 2010
    17,958
    9,423
    I call it, "cranio-rectal inversion". We all suffer from it occasionally.
     
  6. Audioguru

    AAC Fanatic!

    Dec 20, 2007
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    When the electret mic is properly powered then its output level is very low, it needs a preamp with a gain of about 200 to bring the level up to 1V.
     
  7. crobertsbmw

    Thread Starter New Member

    Sep 7, 2011
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    0
    Without amplification I just get a signal of 60hz and a couple milli-voltsno matter how hard I yell. If I amplify this am I really going to see my audio signal? I feel like if I am already seeing a 60hz signal (that I am assuming is ambient) without any amplification over any audio signal then amplifying it won't help.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
    22,194
    1,770
    You have 60-cycle hum from your supply. I'll bet you're trying to use an unregulated wall wart; they won't work very well.

    Here's a preamp for an electret mic; AudioGuru posted almost this exact same circuit a few years back. VR1 should be 500k instead of 470k.
     
  9. Audioguru

    AAC Fanatic!

    Dec 20, 2007
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    The electret mic needs to be connected to the preamp with a shielded audio cable because ordinary wires will pick up mains hum radiation.
     
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