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
    15,648
    2,348
    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
    552
    76
    It requires a DC voltage, check the datasheet.
     
  4. crobertsbmw

    Thread Starter New Member

    Sep 7, 2011
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    0
    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
    16,343
    6,828
    I call it, "cranio-rectal inversion". We all suffer from it occasionally.
     
  6. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    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
    28
    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
    22,182
    1,728
    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

    New Member

    Dec 20, 2007
    9,411
    896
    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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