MAX9814 Microphone Amplifier Module 40/50/60dB Three Gain Levels 100Hz-4kHz Voice Band Automatic Gain Control
 
The MAX9814 module is a fancy microphone amplifier module. It comes with a 20-20kHz electret condenser microphone (ECM) soldered on, and has a few options the user can configure.
The default maximum gain is 60dB, but can be set to 40dB or 50dB linking the Gain pin to Vdd or GND. The Attack/Release (AR) ratio, from the default 1:4000 to 1:2000 or 1:500 can also be changed.
The final audio signal output from the module is about 2Vpp maximum on a 1.25V DC bias. Below are its key specifications: 
 
Automatic Gain Control (AGC)
Three Gain Settings (40dB, 50dB, 60dB)
Programmable Attack Time
Programmable Attack and Release Ratio
2.7V to 5.5V Supply Voltage Range
Low Input-Referred Noise Density of 30nV/√Hz
Low THD: 0.04% (typical)
Low-Power Shutdown Mode
Internal Low-Noise Microphone Bias, 2V
-40°C to +85°C Extended Temperature Range
Quick Note: The MAX9814 module’s output is not 0V in idle state as it has a 1.25VDC offset!