Overview

The MAX9814 is a low-cost, high-performance electret microphone amplifier IC manufactured by Maxim Integrated (Analog Devices). It features an integrated Automatic Gain Control (AGC) system that automatically adjusts signal amplification based on ambient sound levels.

When quiet whisper sounds occur, the AGC automatically boosts gain up to 60 dB; when sudden loud noises or applause occur, the AGC dynamically reduces gain to prevent output clipping and distortion. It is widely used in sound-reactive LED strips (FastLED, WLED), voice recording, and noise detection systems.

Quick reference

Operating Voltage (VCC)2.7 V to 5.5 V DC
Selectable Max Gain40 dB, 50 dB, or 60 dB (configured via GAIN pin)
Automatic Gain Control (AGC)Active compression & limiting to prevent audio clipping
Microphone Bias VoltageIntegrated low-noise 2.0 V2.0\text{ V} bias output
Output Voltage BiasDC-biased at 1.25 V1.25\text{ V} (2 Vp-p2\text{ V}_{\text{p-p}} output swing)
Attack / Release Ratio1:500 (default), 1:2000, 1:4000 (configured via A/R pin)
Operating Current3.0 mA active, 20 µA shutdown

Pinout

Standard 5-Pin Breakout Header

PinNameTypeDescription
1VCCPowerSupply voltage (+2.7 V to +5.5 V DC)
2GNDPowerGround (0 V)
3OUTAnalog OutputDC-coupled analog audio output signal (1.25 V1.25\text{ V} DC offset)
4GAINDigital InputGain setting pin (Unconnected = 60dB, GND = 50dB, VCC = 40dB)
5AR / A/RDigital InputAttack/Release ratio selector (Unconnected = 1:500, VDD = 1:2000, GND = 1:4000)

Specifications

ParameterSymbolMinTypMaxUnitConditions
Supply VoltageVDDV_{DD}2.73.3 / 5.05.5VDC
Supply CurrentIDDI_{DD}—3.04.0mAActive mode
Shutdown CurrentISHDNI_{SHDN}—2035µASHDN = LOW
Maximum Gain (Unconnected)GmaxG_{max}596061dBGAIN=UnconnectedGAIN = Unconnected
Maximum Gain (GND)G50G_{50}495051dBGAIN=GNDGAIN = GND
Maximum Gain (VCC)G40G_{40}394041dBGAIN=VCCGAIN = VCC
Output Offset VoltageVOUT,DCV_{OUT,DC}1.151.231.30VDC bias voltage
Total Harmonic DistortionTHD+NTHD+N—0.04—%f=1 kHzf = 1\text{ kHz}

Gain Configuration Options

GAIN Pin ConnectionMax GainTypical Application
Unconnected (Floating)60 dBQuiet rooms / Long-distance whisper pick-up
Tied to GND50 dBNormal speaking voice / General audio input
Tied to VCC40 dBLoud environments / Concerts / Loudspeakers

Wiring

MAX9814 Breakout Pin→Microcontroller (Arduino / ESP32)Notes
VCC5V (or 3.3V)Clean power source recommended
GNDGNDGround
OUTAnalog Pin A0 (or ESP32 ADC)Analog signal centered at ~1.25V
GAINGND / VCC / UnconnectedSelects 50dB / 40dB / 60dB gain

Common mistakes

  • Power supply noise bleeding into audio output: Amplifying small microvolt signals by 60 dB makes the MAX9814 sensitive to power rail ripple. Add a 10 μF10\text{ }\mu\text{F} capacitor across VCC and GND.
  • Assuming 0V baseline output: The OUT pin has an internal 1.25 V DC offset. Subtract the 1.25 V DC offset (or ~400 ADC counts on a 10-bit 3.3V ADC) in software before calculating peak-to-peak sound amplitude.
  • Using 60 dB gain in loud environments: Leaving the GAIN pin floating in loud rooms causes constant AGC compression, flattening audio dynamics.

Notes

  • Ideal for WLED / FastLED sound-reactive ambient lighting projects using peak-to-peak amplitude measurement (Vmax−VminV_{max} - V_{min}).

Assets & downloads