Make a carbon mic

Versión en español

Picture of a homemade carbon mic

:: Picture no.1 - A carbon mic in wooden box ::

The first microphone consisted of coal mineral grains in a Bakelite case. Two electrodes are connected and flow electrical current through the carbon grains. The current undergoes variations that depend on the resistance of the carbon grains that changes according to the pressure of the air that emits the voice on the microphone.

Picture of interior of carbon mic

:: Picture no.2 - A carbon mic circuit ::

The fidelity of the sound is not great, between 200 to 3000 hertz, but its sensitivity is because it manages to capture distant sounds from the environment.

The replica I built was inspired by the microphone built by Simplifier.

Recordings made:

J.S. Bach BWV 974 by Glenn Gould.

Chopin nocturne op.9 by Valentina Lisitsa.

S.L. Weiss, Chacona G minor by Mark Anthony McGrath.

Due to the limited range of frequencies that it can capture, the best results are obtained by recording music with a single instrument, for example a piano or guitar.


The main element is two bars of carbon extracted from type D batteries.

As a transformer I used one extracted from the power source of a cell phone.

Here the electrical schematic:

Carbon Mic Circuit

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