Electret Mic Breakout Board Hookup Guide
LightningHawk 
Hardware Overview
Hardware
The Electret Mic Breakout Board only has three pins: VCC, GND and AUD. You can power this device from 3.3V to 5V, so it is a great compliment to most microcontroller units. For the amplification, we used Texas Instruments OPA344 rail-to-rail precision amplifier to give you maximum output swing.
Schematic
The gain of the amplifier is set by R5/R4 which is approximately 82V/V. Simulation and testing puts the gain closer to 60V/V.
Frequency Response
What this tells you is that you will see the same gain across the frequency spectrum that is picked up by the mic (100Hz-10KHz). The input of the amplifier is biased at 1/2 VCC. The very small AC voltage output by the mic rides on the DC offset and gets amplified through the OPA344. The output from the "AUD" pin is also at 1/2 the supply voltage, so it can be connected directly to the ADC of microcontroller. In quiet conditions, the ADC will ideally read 1/2 the full scale or 512 on a 10-bit converter.