Dual Electret Preamp

A dual-channel electret microphone preamp designed for simple, low-noise audio applications.

Overview

The Dual Electret Preamp is a compact PCB I designed to amplify the signals from two electret microphone capsules. It brings both preamp channels onto a single board, making it a practical starting point for homemade stereo microphones, experimental capsule arrangements, and sound-recording projects. The idea is to make it easier to explore microphone building—from trying different capsules to discovering how their placement shapes the sound.

The Build

The board is built around an LM358 dual op-amp, with two independent preamp channels. Each channel has its own jack output and gain control, while the electret capsules can be quickly replaced to experiment with different microphones. Other pin-compatible dual op-amps can also be explored, provided their electrical requirements suit the circuit. I housed this prototype in a simple plastic enclosure, but the PCB can be integrated into a custom microphone body or another enclosure suited to the project.

Small Board, Simple Build

Shown here beside an electret capsule for scale, the PCB makes a compact, beginner-friendly project with entirely through-hole components that are easy to handle and solder. It runs well on a standard 9V battery, providing a quiet power source without the hum that some external supplies can introduce. Battery life will depend on the components and battery used, but the circuit’s modest power requirements make it well suited to extended recording sessions.