MAX9814 Electret Microphone Amplifier with Auto Gain Control
I use these in all of my audio reactive projects, I use them with FFT, the Automatic Gain Control and adjustable Attack/Release ratio are really handy and can be controlled on the fly from your code. Just connect the AR and AGC to pins on your controller and then set them High, Low or leave them floating Input). I also use a 100uF blocking capacitor in series between the Out pin and the controller.
// Set Gain LOW 50dB, HIGH 40 dB, INPUT 60dB
// pinMode(gainPin, INPUT),
digitalWrite(gainPin, HIGH),
// Set Attack and Release Ratios
// LOW 1:500, HIGH 1:2000, INPUT 1:4000
pinMode(ARpin, INPUT),
// digitalWrite(ARpin, LOW),
This fully assembled and tested board comes with a 20-20KHz electret microphone soldered on. For the amplification, it uses the MAX9814, a specialty chip that is designed for amplifying electret microphones in situations where the loudness of the audio isn't predictable.
This fancy microphone amplifier module is a step above the rest, with built-in Automatic Gain Control. The AGC in the amplifier means that nearby 'loud' sounds will be quieted so they don't overwhelm & 'clip' the amplifier, and even quiet, far-away sounds will be amplified. This amplifier is great for when you want to record or detect audio in a setting where levels change and you don't want to have to tweak the amplifier gain all the time.
The chip at the heart of this amp is the MAX9814, and has a few options you can configure with the breakout. The default 'max gain' is 60dB, but can be set to 40dB or 50dB by jumpering 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 output from the amp is about 2Vpp max on a 1.25V DC bias, so it can be easily uséd with any Analog/Digital converter that is up to 3.3V input. If you want to pipe it into a Line Input, just use a 1-100uF blocking capacitor in series (100uF sounds best).