Two-input audio mixer

How it works

VR1 and VR2 adjust the two input levels, while VR3 changes the balance between them. VR4 is an optional master output control. One possible experiment is combining a dynamic microphone signal with a music source.

Different sources can have very different output levels. Set the input controls to avoid overdriving the mixing stage; reducing the final volume cannot undo clipping that has already occurred.

On the bench

Check whether the microphone requires additional gain. Keep signal grounds consistent and use screened cable to reduce hum, especially on the microphone input.

Resources & provenance

Rewritten from the original circuits/aum/lj3on1t_aum013.php page. Component values and historical performance claims have not been independently bench-tested. The circuit figures have had their watermarks removed.