Very High Gain Microphone


This project is my father’s idea, he found in an old army surplus store with a radar dish and mount.  His idea was to make a very high gain microphone to be able to listen to almost anything, like birds or whatever else you want.  

The electronic circuit is simple, just an electret’s microphone mounted in the focal point of the dish. An amplifier made of two op-amps, the first to give more gain and the second and most important is the AGC "Automatic Gain Control." With the AGC the audio signal you hear weather far or near, will be the same.  In the schematic there is no power output for the audio, you can use a simple LM386 to drive a head phone. It is incredible what you can hear with this high gain dish mounted microphone! Have fun.



Amplifier Schemetic

11 Comments to “Very High Gain Microphone”

  • pharmacy tech April 10, 2010 at 1:26 am

    My cousin recommended this blog and she was totally right keep up the fantastic work!

  • admin April 10, 2010 at 5:12 pm

    Hi Chased,

    Thanks for your positive comments it’s always welcome


  • Armando Codina July 28, 2010 at 9:04 pm

    I have searched all over google for info on this topic, I finally found a good post, looking forward to coming back!

  • Kathryn August 27, 2010 at 12:43 pm

    The good article assited me a lot! Saved the site, very excellent categories everywhere that I read here! I appreciate the information, thank you.

  • DreamCat January 3, 2011 at 3:40 am

    R3 and R4 is real need in this circuit?

  • admin January 3, 2011 at 3:42 am

    Yes they are,

  • DreamCat January 4, 2011 at 4:03 pm

    the + input of U1A has been biased 1/2 VCC, and AC-coupled to ground.
    so I think they are not required.

  • Sylvain Bissonnette January 4, 2011 at 4:19 pm

    Yes you need those resistor the op-amp work with only a single supply

  • DreamCat January 5, 2011 at 4:50 am

    I still think they are not needed.

    beacause there has negative feedback, and the “+” input has been biased to 1/2 Vcc. so the “-” input can also got a 1/2 Vcc.

    this circuit has AGC, very nice. I will make one for my self…thanks.

  • Yajie Ji February 3, 2012 at 1:04 pm

    What's the type or the "C6-4700pF"? CBB or any others?
    Thank you very much!

  • titone January 18, 2013 at 9:11 am

    "dream cat" is absolutely right.
    R2 goes to Vcc2 and R1 goes away.

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Please note

All my source codes were taken from my personal projects.

Everything is for your information only. The C/C++ codes have been written
with ICCAVR. You can find the header and source CRT files by downloading their compiler.

All is for your information and everything is AS IS without any warranty of any kind. No other files are available and I don't make any modification for any body.



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