This project is a simple balanced stereo line level mixer. One input module (LIM-1) is required per stereo input channel and one output module (LOM-1) per stereo output channel. The HPM-1 headphone amplifier can be used for headphone connection to the stereo bus.

This project makes use of the following modules:

LIM-1 (one per stereo input channel)

LOM-1 (one per stereo output channel)

HPM-1 (optional headphone amplifier)

MPM-3C (optional LED metering)

PSU-8 (triple rail power supply)


This project was designed to allow 4 stereo devices (balanced or unbalanced) to connect to the monitor feed separately from the DAW feed. Devices such as CD players, music players, mixers etc can be connected. The modules connect together in a power and signal bus along the front panel.

A switch on the front panel of the input channel can be used to disconnect the input from the stereo bus completely, using a relay for isolation. This is optional and can be left off and the relay pads bridged if not required.

The photographs show the MPM-3C LED metering attached, however this is probably unnecessary.

LMX-1 Internals











Line Mixer internal assembly showing modules along front panel


LMX-1 Front Panel








Line Mixer prototype front panel. This is 2RU high and a half-rack width


LMX-1 Rear Panel







Rear Panel view of the Line Mixer. Power was supplied externally due to space limitations.