Simple Microphone Amplifier

Discussion in 'The Projects Forum' started by John Paul Senosin, Oct 3, 2016.

  1. John Paul Senosin

    Thread Starter New Member

    Sep 29, 2016
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    Guys, i need help.....
    I want to build a simple microphone amplifier, also i dont have an electret microphone (all of the local electronics stores dont have them) but they have a condenser microphone and also i have a 3 watt 8 ohm speaker =)
     
  2. Kermit2

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  3. AlbertHall

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  4. Kermit2

    AAC Fanatic!

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    He said the stores have CONDENSER microphones.

    I do not see any mention of ribbon mics...

    So where did I go wrong Albert?
     
  5. AlbertHall

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    Neither do I.
    Should've gone to Specsavers.
     
  6. AnalogKid

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    Aug 1, 2013
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    An electret microphone element is a special case of a condenser or capacitor microphone. many places use the terms interchangeably, although technically they are different. The odds are that your local stores have some electret mics. Are you talking about complete microphones, or just the microphone element inside? Any makes or model numbers?

    Also, the circuit in post #2 has problems, and cannot drive an 8 ohm speaker well. If you are not dedicated to an all-discrete transistor circuit, consider circuits based on the LM386 audio power amplifier. It was built from the ground up for this application. Depending on the sensitivity of your microphone, you might need to ad a 1-transistor preamp ahead of it.

    ak
     
  7. John Paul Senosin

    Thread Starter New Member

    Sep 29, 2016
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    So i need to connect my microphone to a preamp using transistors and the output of the preamp goes to the amplifier, right?
    And also im talking about the microphone element itself and not a complete mic
     
  8. John Paul Senosin

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    Sep 29, 2016
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  9. Kermit2

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    If it is driving an 8 ohm speaker and you want 1/2 watt of music it will overheat. If you just want to amplify a mic and send the signal to a REAL amplifier then it will work ok.
     
  10. AnalogKid

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    Correct. It won't overheat because the 1.2K resistor in the Q2 collector limits the max current to a minuscule 4.2 mA. Even if this were the continuous output current, which it is not, the output power into 8 ohms is 140 microwatts. As before, this circuit will amplify something, but cannot drive an 8 ohm load without very low output power and significant distortion.

    ak
     
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