Introduction

The MAX9814 is a complete microphone amplifier with automatic gain control (AGC), featuring low-noise amplification and adjustable gain settings. This module provides clean audio signal conditioning for Arduino sound detection, voice recognition, and audio recording applications.

Key Features

Technical Specifications

Pin Configuration

Pin	Label	Description	Arduino Connection
1	VDD	Power (2.7-5.5V)	5V
2	GND	Ground	GND
3	OUT	Audio Output	A0 (Analog Input)
4	GAIN	Gain Selection	See gain selection table
5	AR	AGC Release Control	Optional capacitor to GND

Gain Selection

Basic Wiring (Arduino)

// MAX9814 Connections:
// VDD → 5V
// GND → GND
// OUT → A0 (Analog Input)
// GAIN → (See gain selection table)
// AR → (Optional 1μF capacitor to GND)

// For best results:
// - Keep microphone away from noise sources
// - Use shielded audio cable for long connections

Basic Sound Detection

const int micPin = A0;

void setup() {
  Serial.begin(9600);
}

void loop() {
  int soundValue = analogRead(micPin);
  
  // Remove DC offset (approx. VCC/2)
  int adjustedValue = abs(soundValue - 512);
  
  Serial.print("Sound Level: ");
  Serial.println(adjustedValue);
  
  // Simple threshold detection
  if(adjustedValue > 50) {
    Serial.println("Sound detected!");
  }
  
  delay(50);
}

Advanced Applications

// FFT analysis with Arduino
#include "arduinoFFT.h"

arduinoFFT FFT;
#define SAMPLES 128
double vReal[SAMPLES];
double vImag[SAMPLES];

void setup() {
  // Sample audio at consistent intervals
}

void loop() {
  for(int i=0; i

// Add capacitor to AR pin for:
// - Smaller value: Faster AGC response
// - Larger value:  Slower AGC response
// Typical values: 1μF to 10μF

// Example wiring:
// AR pin → 4.7μF capacitor → GND
// (Better for music with dynamic range)

// Detect sudden loud sounds
unsigned long lastClap = 0;
const int clapTimeout = 500;

void loop() {
  int peak = 0;
  for(int i=0; i<10; i++) {
    int val = abs(analogRead(micPin) - 512);
    if(val > peak) peak = val;
    delay(1);
  }
  
  if(peak > 100 && millis() > lastClap + clapTimeout) {
    lastClap = millis();
    Serial.println("Clap detected!");
  }
}

// Record to SD card
#include 

File audioFile;

void setup() {
  SD.begin(4); // CS on pin 4
  audioFile = SD.open("audio.raw", FILE_WRITE);
}

void loop() {
  int sample = analogRead(micPin);
  audioFile.write(sample >> 2); // 8-bit conversion
  delayMicroseconds(125); // 8kHz sampling
}

Troubleshooting