Matrix mixer with four input and two output channels plus headphone jack.
Mix 01 is an extensible 4 in / 2 out matrix mixer with a dedicated stereo headphone output. The module is suitable both for audio and control voltage mixing. Several Mix 01 modules can be combined to make a bigger matrix with more inputs and outputs.
http://www.rebeltech.org/products/mix-01/
This Module is currently available.
$115