Electret microphones are capable of high-quality output, and are prized for their smooth frequency response. However, unlike other types, they can’t simply be plugged directly into a mixing desk. Instead, they require special high-impedence circuitry to extract the audio signal for recording. [DJJules] is a big fan of these microphones, and decided to build a high-quality, easy to use circuit that he has shared with the community.
The goal of the project was to create a circuit to match the TSB2555B electret capsule that could be used with phantom power, and that could be built with easily obtainable parts. [DJJules] had used FETs in the past, but grew tired of routinely having to hunt for obsolete parts. Instead, this design relies on a dual OPA1642 op-amp, with its low quiescent current meaning it’s perfect for running off phantom power. This means the microphone needs no batteries, and using a dual op-amp enables the circuit to properly drive a balanced audio connection.
The circuit is designed to fit inside a common BM700 or BM800 microphone body, and the PCB can be ordered from PCBWay for those interested in building their own. There’s also a saddle on Shapeways that’s designed to neatly mount the electret capsule within the housing.
The final results are impressive, and this project would make a great entry into the DIY microphone space for anyone eager to start building their own gear. Of course, there are simpler b ..