Mic Preamp front panel

A 4-channel microphone preamplifier with lots of options, including bypassable inserts.

 

Overview

This microphone preamplifier is modular in design, with a set of circuit boards per channel, allowing as many or as few channels to be constructed as needed. In addition the metering module plugs into the preamplifier board and can be left out or replaced with a different one if required. The modules used for this project are:

  1. MPM-3 mic preamp module
  2. MPM-3 gain switch module
  3. MPM-3 metering module
  4. ABM-1 insert bypass module
  5. PSU-7 single rail 48V power supply module
  6. PSU-8 triple rail (+/-16V, 5V) power supply module

The preamplifier uses a rotary switch to set the gain in 6dB increments from -6dB to +60dB and also has a gain trim pot to allow further adjustment of +/-6dB from the set gain switch value. Two switches per channel allow switching of phantom power for the channel and activate the insert for any insert signal processing that may be connected. For example, a compressor, distortion, gating or just a transformer for colour or isolation may be selectively inserted with the switch.