Adafruit Industries 1713

This elegant microphone amplifier module features a built-in automatic gain control (AGC) function. The AGC in the amplifier means that nearby "loud" sounds are attenuated to prevent the amplifier from overloading and "clipping," while faint, distant sounds are still amplified. This amplifier is ideal when you want to record or detect audio in environments with varying sound levels without frequently adjusting the amplifier gain.

The core chip of this amplifier is the MAX9814, which can be configured via the breakout board. The default "maximum gain" is 60dB, but it can be set to 40dB or 50dB by connecting the gain pin to VCC or ground. You can also change the attack/release ratio from the default 1:4000 to 1:2000 or 1:500. The amplifier output is approximately 2Vpp maximum at a 1.25V DC bias, making it easy to use with any ADC with an input voltage up to 3.3V. To connect it to a line input, simply connect a 1uF DC-blocking capacitor in series.

Each order includes one assembled and tested PCB with a pre-soldered electret microphone and a short section of header pins.

• Supply voltage: 2.7V - 5.5V, current 3mA
• Output: 2Vpp at 1.25V bias
• Frequency response: 20Hz - 20kHz
• Programmable attack and release ratio
• AGC with selectable maximum gain: 40dB, 50dB, or 60dB
• Low input-referred noise density: 30nV
• Low THD: 0.04% (typical)