a good starting point – stethoscope mic made from a contact mic and preamp
power supply for a condenser mic
Electret Microphone and Pre amp:
“Description: This small breakout board couples an Electret microphone (100Hz–10kHz) with a 60x mic preamplifier to amplify the sounds of voice, claps, door knocks or any sounds loud enough to be picked up by a microcontroller’s analog-to-digital converter. Each breakout comes fully assembled and works from 2.7V up to 5.5V.
The Electret Mic Breakout translates amplitude (not volume) by capturing sound waves between two conducting plates (one a vibrating diaphragm and the other fixed) in the microphone and converting them into electrical waves. These electrical signals are then amplified and picked up by your microcontroller’s ADC.”
This TI Precision design details the design process for a preamplifier to be used with electret microphone capsules. It explains the basic construction and operation of an electret microphone and uses an OPA172 to amplify the output of the microphone to common analog line level voltages.
Circuit Board Resources :