Ultra-Simple Mono Audio Mixer #1

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This project is an older design and has most likely been superceded by a newer one.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

The simplest mixer ever. You can change the 39K feedback resistor to change the gain. Make the resistor value higher for higher gain or lower for less gain. The input gain pots can be anything from 10K to 1Meg, the value is not critical. Adjust the 100K feedback resistors in the headphone amp section to change the gain, again higher resistor values make the signal louder, lower resistor values make the signal softer. You could run this off of two nine volt batteries too.

Ultra-Simple Mono Audio Mixer Circuit Schematic