This is a strictly DIY project, I've only built it on plug-in breadboard to prove the operation.


It is intended for the traditional "bare electret capsule" style PC microphones that have a capsule in a casing or stand with a cable and plug - no other electronics.

Or, for use with your own electret capsule.

It gives a useful amount of gain, without needing any additional power supply - it runs from the PC supply for the mic and passes that on, somewhat reduced to the mic capsule.


You may need to adjust the series power filtering resistors, or adjust the bias resistor value, to get optimum results; it's a "proof of concept" design that may well need tweaking for different mic capsules and different PC (or other) mic inputs.



The proof-of-concept build, working on a breadboard:

For this, a mic capsule was connected directly at the input & the PC plug cable has red and black to tip & ring, with the bare wire being the scree to the plug body (sleeve).

The green wire connects the negative of the power decoupling capacitor at the top to the circuit ground at the very bottom.

This did not have the 0.1uF across electrolytic cap, that is an optional refinement for better HF filtering. Likewise the emitter resistor shown on the schematic above; that may improve quality slightly - try without it or experiment with different low values, in the 10 Ohm to 100 Ohm range & wee what works best!