Using Pulp Logic’s E-Tret circuit as a starting point, I made a 3U 4HP input module for stereo electret microphones. For each channel, it provides plug-in-power, pre-amplification, modular-level amplification with adjustable gain, and LED clipping indicator. I’m using it with LOM Audio Uši, but it should work fine with every pair of electret capsules.
It’s my first analog module, and the first time I designed custom PCBs: the green one for the front-facing components, and the black one to use as front panel. The other two circuits are arranged on protoboards.
Below is the schematic for anyone interested. The single-channel pre-amp and amp is a copy of Pulp Logic’s 1U E-Tret circuit. The clipping LED circuit is from here.
Here’s a link to the plan for the protoboards. It’s quite messy, it’s just a guide I used for placing and soldering components and wire, it’s not a PCB.
