XLR Electret Preamp

A balanced electret microphone preamp powered directly from 48V phantom power.

Overview

The Electret XLR Preamp is a balanced microphone preamp designed to work with most electret capsules. It is powered directly from 48V phantom power. It provides a low-noise signal path while keeping the circuit compact enough to fit inside any tubing that could be used as a microphone enclosure.

The goal was simple: build a practical, self-contained preamp that turns an inexpensive electret capsule into a proper balanced XLR microphone, without requiring an external power supply or additional electronics.

The Build

It is really straightforward. There is only one SMD component in this build: the OPA1642 op-amp. You may or may not solder the XLR male connector directly to the circuit, it’s up to you.

You can also use a JST connector or a terminal block for the capsule. This allows for quick capsule swapping for different situations.