Ultra-Simple Stereo Input Audio Mixer

Ray Wilson authored this content while he was actively running MFOS as the founder and resident genius.
We retain the content because it reflects a valuable point of view representing that time and place.

Article by Ray Wilson

This project is an older design and has most likely been superceded by a newer one. However, it is still a viable design and useful for your home-brew synth. Sorry but most of these do not have circuit descriptions, parts lists or PC board layouts (They really put the 'Y' in DIY). The designs are here for individual and educational use only and no permission is given for large scale production for sale.

This is an intermediate to advanced project and I do not recommend it as a first project if you are just getting started in synths or electronics. Only the circuit and some explanation are shown here. A lot of project building, troubleshooting and electronics experience is assumed. Additionally, electronic equipment ownership (scope, meters, etc.) is taken for granted. If you are interested in building this project please read the entire page before ordering PC boards to ensure that the information provided is thorough enough for you to complete the project successfully.

Introduction

This mixes stereo input sources. You can change R5 and R8 for more or less gain (higher value more gain lower value less gain). The input gain pots can be anything from 10K to 100K, the value is not critical. You could run this off of + and - 12 to 15 volts if you want to. Put a switch in series with the batteries so you can turn the unit on and off.

Ultra-Simple Stereo Input Audio Mixer Circuit Schematic