Ultra-Simple Mono-in Panning Mixer Parts Layout

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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