How to build Low impedance microphone amplifier

December 13, 2010 - category: Audio amplifier


The circuit is a microphone amplifier for use with low impedance (~200 ohm) microphones. It will work with stabilized voltages between 6-30VDC. If you don't build the impedance adapter part with T1, you get a micamp for higher impedance microphones. In this case, you should directly connect the signal to C7.

Schematic diagram

Low impedance microphone amplifier-Schematic diagram

Layout of board

Low impedance microphone amplifier-Layout of board

printed PCB

Low impedance microphone amplifier-printed PCB


  • R1=15k
  • R2= 150k
  • R3= 2k2
  • R4= 820
  • R6= 10k
  • R7= 10k
  • P1= 1M
  • C1= 3k9
  • C2= 100u
  • C3= 22u
  • C4= 4u7
  • C5= 470u
  • C6= 10u
  • C7= 100n
  • C8= 47u UNIPOLAR
  • D1= 1N4148
  • U1= TL081
  • CN1= SIL6

circuit from http://www.electronics-lab.com/

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