2 x 3:1 mixer (or 6:1)

Output of top mixer is normalled to the bottom mixer to give a 6:1 mix.

Outputs are phase correct (e.g. the output audio is not inverted).

The input signals are neither boosted nor attenuated (unity mixing). their resultant sum is the output.
e.g. if input 1: 2v, input 2: 4v, input 3: 3v
then output1: 9v (input1 + input2 + input3 = 2v + 4v + 3v = 9v).

NOTE: Version 2 of the Unity Mixer has two sets of jumpers on the main pcb. These allow the top and bottom sum to be set to -6dB attenuation instead of unity gain. This creates more headroom when summing higher amplitude sources like raw VCO signals.