Late to the party – schematic

[scwis]

Great point Neil.

I’ve used this circuit (adapted from THIS ARTICLE) to combine stereo output into a mono input with a passive circuit.

I have also used resistors of lower Ohm values for inputs and outputs lower than line level.

1/8th watt resistors seem to work OK at low audio power levels

The circuit seems to work equally well as a splitter or a combiner.

Experimental broadcasting for a better tomorrow!