The simple audio mixer circuit is built on common base principle, where input voltages are transformed in alternative currents wich are summed to form the alternative current component for the ...

This audio mixer circuit schematic we propose here is built around four amplifiers, which are current controlled, all of them incorporated in IC SSM2024, produced by Precision Monolithics Inc. (PMI).

That's it. Now we've got a simple audio mixer that'll keep the inputs from driving each other, and get the audio out from two sources to your speakers or headphones on demand.