MIC Pre-amplifier

  • Rajkumar Sharma
  • 24427
  • moderate
  • Tested


This project is a microphone pre-amplifier based on LM358.


This is easy to construct microphone pre-amplifier project using compact electret condenser microphone. The pre-amplifier is important building block of many audio communication systems. Circuit has been built around Op-Amp LM358.

  • Power supply : 5 to 12 VDC @ 10 mA
  • Output: Gain Approx. 100
  • On-Board electret condenser microphone
  • Header connector for connecting of power supply input and audio output
  • Power-On LED indicator
  • Four mounting holes of 3.2 mm each
  • PCB dimensions 35 mm x 40 mm


Parts List



  • robert

    thanks for this

    4 years ago
  • Caleb

    Could I replace the mic you used with an XLR input? Trying to figure out how to make an adjustable XLR preamp for cameras.

    4 years ago
    • Electronics Lab

      The mic output is in the range of mV and needs a bias resistor R2 in order to work. In addition you can feed a small signal like that directly on C3 and omit R2 resistor so you get an amplified signal on the output.

      4 years ago
  • Sivanand

    LM358 is not a low noise IC, Use of TLO71 / TLO81 would give better low noise response, cheap and easily available.

    4 years ago
  • Pablo

    The foil side of the PCB image has to be mirrored. In that case your logo and the “800A” would be backwards.

    2 years ago
    • I’ve uploaded PCB in PDF file in the downloads above. Thanks

      1 year ago
  • Pratyusha

    Hello, I have given the same circuit in the bread board, & i have given input from my phone with the help of 3.5 mm audio jack…..but i couldn’t hear the output through earphones or audio jack. I can guess some processing is happening. The earphones are working properly,and i couldn’t find out where the problem is…..please help.

    1 year ago
    • Could you explain a little more about your setup. Have you removed the mic and R2 bias resistor? I would suggest to start a new topic on forum. This is the best place to discuss your project. https://www.electronics-lab.com/community/

      1 year ago

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