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SSM2167 Microphone Preamplifier Board Low Noise Mono Audio Amplifier 3-5V

$15.52 USD

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SSM2167 Microphone Preamplifier Board — Low Noise, Built-In Compressor, 3–5V

The SSM2167 is a complete microphone preamplifier and compressor IC from Analog Devices, designed for voice capture applications where consistent audio levels are required regardless of speaker distance or volume. Unlike a simple op-amp preamp, the SSM2167 integrates a voltage-controlled amplifier (VCA) with automatic gain control (AGC) — automatically reducing gain when the input signal is loud and increasing it when quiet, producing a compressed, normalized audio output ideal for voice transmission, recording, and speech recognition.

This breakout module mounts the SSM2167 with all required passive components, an onboard electret microphone capsule, and exposes power and audio output pins for direct connection to Arduino, ESP32, Raspberry Pi, or any audio ADC.

Key Specifications

IC: Analog Devices SSM2167
Supply Voltage: 3V – 5V DC (single supply)
Supply Current: ~1.5mA typical
Input: Onboard electret microphone capsule (omnidirectional)
Output: Analog audio (single-ended, AC-coupled)
Frequency Response: 100Hz – 10kHz (voice band optimized)
Noise Floor: Low noise design, suitable for quiet voice capture
Compression: Built-in downward expander + compressor/limiter
Compression Ratio: Adjustable via external resistor (COMP pin)
Attack/Release Time: Adjustable via external capacitor
Output Level: Adjustable via onboard potentiometer (some board variants)
Operating Temperature: −40°C to +85°C

How the SSM2167 Compressor Works

The SSM2167 uses a feed-forward VCA architecture. The input signal level is continuously measured by an internal RMS detector. When the signal exceeds the compression threshold, the VCA gain is reduced proportionally — preventing clipping and maintaining a consistent output level. When the signal drops below the noise gate threshold (downward expander), gain is further reduced to suppress background noise during silence. The result is clean, consistent voice audio with minimal clipping and reduced background noise — without any DSP or software processing.

Compression Ratio Adjustment

The compression ratio is set by a resistor connected to the COMP pin:

COMP open (no resistor): ~1:1 ratio (no compression, linear preamp mode)
COMP = 100kΩ to GND: Moderate compression (~2:1)
COMP = 10kΩ to GND: Heavy compression (~10:1, limiter behavior)

Most breakout modules include a fixed resistor for moderate compression suitable for voice applications.

Pin Connections (Typical Breakout Module)

VCC → 3.3V or 5V DC
GND → Ground
OUT → Audio output (connect to ADC input, audio amplifier, or line-in)
Onboard electret microphone is pre-connected internally

Connecting to Arduino (Analog Audio Capture)

VCC → 3.3V (preferred) or 5V
GND → GND
OUT → Arduino A0 (analog input)
Read with analogRead(A0) at 8–10kHz sampling rate for voice quality audio
For better quality, use an external I2S ADC (e.g., INMP441, MAX9814) or audio codec

SSM2167 vs. MAX9814 vs. MAX4466

SSM2167: Built-in compressor/limiter + noise gate. Best for voice transmission where consistent levels are critical (walkie-talkie, intercom, IoT voice). Requires 3–5V.
MAX9814: Auto gain control (AGC) preamp, adjustable gain (40/50/60dB), no compressor. Better for general audio capture with variable gain. Requires 2.7–5.5V.
MAX4466: Simple fixed-gain preamp (adjustable 25–125×), no AGC or compression. Best for applications needing a specific fixed gain. Requires 2.4–5.5V.