Simple condenser mic preamp circuit using 2N3904

If you want to learn about microphone or little use. This is a simple condenser MIC preamp circuit diagram. It changes the sound to electrical signals before sending to a power amplifier. To drive a general speaker.
You can read how condenser microphone works later.

Simple condenser mic preamp circuit using 2N3904

How it works

First of all, we connect a 9V power supply to the circuit. Secondly, a resistor R1 passes an electrical current to biased the Microphone (MIC1). The R1 is a current limiting resistor for MIC1.  It is ready to work. When we make a sound to MIC1, it causes the electrical signals to change.

Then, the sound signal flows through a coupling capacitor-C1. Because It will block DC current not pass.

But the signal is very weak. So, it needs helping with a transistor Q1 to increase the signal up.

Next, the signal goes to B of Q1 to amplify more power to out of C—output.

After that, the coupling capacitor C2 pass the AC signal to the output, a tone control preamplifier.

Also, you can connect the output with a headset to convert an electrical signal into sound.

The function of many resistors

  • The R1 is a current limiting resistor for MIC1.
  • Resistor R2 is biased feedback signal from output to input by connecting between  B and  C of the transistor Q1. To provide stability for the good work.
  • Both R3 and R4  act as to keep a bias voltage level to be suitable.

How to apply it

If you are beginner, here is Connecting a Condenser Microphone Preamp with an amplifier system. Look at below, You should have a tone control preamplifier. Because the output of circuit has lower signal.

Connecting a Condenser Microphone Preamp with an amplifier system

Circuit kit

This circuit does not have a PCB layout. But you can solder them on the universal PCB Board. Which it may be that difficult for you.

Condenser Microphone Preamplifier circuit kit

I recommend you  Condenser Microphone with Pre-Amp 9VDC Electronic Circuit Kit by Manie Power (Future). I love it.

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I always try to make Electronics Learning Easy.


  1. sachin

    Can u understand even 1 word of what you have typed ?

  2. John-Michael Holmes

    does this work with other mics?if not why and what would change?

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