741 Electret Pre-Amp

Discussion in 'General Electronics Chat' started by Razor Concepts, Jan 22, 2009.

  1. Razor Concepts

    Thread Starter Active Member

    Oct 7, 2008
    212
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    I want to make an electret pre-amp as a sound sensor for a microcontroller. Here is a circuit I found:
    [​IMG]
    I don't need precision, I just need to tell the difference between loud noise and soft noise - will this circuit do the trick? I also have a lm311 lying around but I'm thinking that the 741 will be good enough. Thanks!
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
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    I don't seem to be able to open your attachment.

    hgmjr
     
    Last edited: Jan 22, 2009
  3. Razor Concepts

    Thread Starter Active Member

    Oct 7, 2008
    212
    1
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    It should amplify. How are you going to indicate loud and soft?
     
  5. Razor Concepts

    Thread Starter Active Member

    Oct 7, 2008
    212
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    I will be using a 10 bit ADC. I think 5v over 1024 is a 5 millivolt resolution.
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    You could rectify the sound to DC and use a voltage comparator. If you still go with the ADC, it will still be a good idea to rectify the output.
     
  7. italo

    New Member

    Nov 20, 2005
    205
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    I don't see a preamp i see a lousy switch. A comparator will do you more good.
     
  8. flat5

    Active Member

    Nov 13, 2008
    403
    17
    [​IMG]

    You get what you pay for?

    There is no base bias on the transistor.
    Not a great circuit. You can find a better one...for free.
     
  9. bertus

    Administrator

    Apr 5, 2008
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  10. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The lousy old 741 opamp is too noisy (hisssss) to be a mic preamp.
    The circuit with the 741 and with the unbiased transistor on the right side is a joke. It shows a 3-wire electret mic that is very rare. A 741 is spec'd with a 30V supply and most will not work from a 5V supply.
     
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