Adafruit electret microphone with built in amplifier adafruit 1063 the adafruit electret microphones with adjustable gain amplifier feature a built in microphone and use the max9814 microphone amplifier chip theres a small trimmer pot on each one to adjust the gain between 25x and 125x so that you can minimise volume related distortion they can be supplied with 24 to 5v dc and are capable of rail to rail output with a dc bias of vcc2 be careful when selecting your power supply 5vpp may