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A stereo output mixer of my own design
Front-Panel-Express MOTM style panel

A simple 4-IN, 2-OUT matrix mixer. Inside are two identical 4-input mixers. Each input is sent into both mixers, through separate level pots. Two extra inputs (1R and 2R) give a total of six inputs, these going only to the right mixer. 1R and 2R are normally taken from the 1 and 2 inputs. Gain is jumper-selectable to be either 1.0 or 0.5. The 50% gain is better for output to an external mixer, and reduces the chance of clipping when mixing strong signals.

This project was all DIY, built on a MUUB-4 PC board from Tellun. (One circuit trace cut per mixer was needed for the custom jumper.) It uses eight log taper Vishay-Spectrol pots, some of the last ones available from Synthesis Technology.

View the schematic, and the block diagram.

I chose to use tightly twisted pair wiring instead of shielded cable, due to the short lengths and the density.