Ostrawa [ɔs’trava] is a full stereo four-channel voltage controlled mixer featuring a stereo mixing bus, one stereo auxiliary send per channel (switchable between pre and post VCA) with stereo returns, clickless muting, individual level meters, and a super clean and DC-coupled signal path designed with high-quality VCA and opamp chips.

We have carefully crafted Ostrawa's voltage control response to achieve what we believe to be the optimal user experience found in a Eurorack mixer. The design features an elaborate control circuit that combines the internal voltages generated by the panel potentiometers with external CV over volume and stereo balance. The result is a natural attenuator response that constrains VCA gain to a usable range while minimizing distortion.

Ostrawa is a sister module to Xaoc devices Praga. It features a very similar response characteristics and similar layout of controls with some functional differences resulting from stereo inputs and limited panel space. Multiple Ostrawa and Praga units may be chained for a custom configurable mixing system. An expander called Bohumin is also available.