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Originally Posted by Andrew
You need to start with a condensor microphone element (available from Radio Hut or from Digikey). A condensor mic takes sound waves and converts them into a change in capacitance.
You might be able to find a data sheet for the condensor microphone which gives you a circuit to preamplify it.
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Andrew,
Not exactly...True condensor mics have built in circuitry that make the conversion from capacitance to voltage internally and they are very expensive ($2000-5000). Most mic elements that you find (cheap at Digikey $2-$4) will be electret condensor mics. These elements have a permanent electrostatic field and as the plates of the condensor (capacitor) vibrate with sound the element outputs a real tiny voltage. This voltage is at a very high impedance so there is an amplifier to lower the impedance and add some gain built right into the mic. For this reason it is necessary to add a little DC power to the mic. Electret spec sheets will have typical power supply wiring, but it is usually very simple, a resistor to power supply is usually all it takes. Follow up with a coupling capacitor to a preamp and you are all set. LM324 are quad op amps optimized for single ended power. You still have to add bias wiring but they are cheap and available and have reasonable gain and distortion.