Full Stereo Voltage Controlled Mixing Console
Model of 1966

  • Ostrawa
  • Ostrawa
  • Ostrawa
  • Ostrawa


Ostrawa [ɔs’trava] is a fully 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, a sister module to Xaoc Devices Praga, features similar response characteristics and layout of controls with some functional differences due to its stereo inputs and limited panel space. Multiple Ostrawa and Praga units may be chained for a custom configurable mixing system.

For detailed description, please refer to the manual.

  • Full stereo architecture
  • Natural volume response
  • Channel level indicators
  • Stereo auxiliary send and stereo returns
  • Clickless channel muting
  • Expandable by chaining more units and optional expander modules
Technical details
  • Eurorack synth compatible
  • 20hp wide, 46 mm deep (including the ribbon cable and bracket)
  • Current draw: +180mA/-150mA
  • Reverse power protection
  • Multiple Ostrawa and Praga units may be chained to provide a cascaded sub-mix setup
  • A dedicated Bohumin expander adds a second full stereo AUX bus with voltage control over the amount of the effect on each channel of Ostrawa. Bohumin also features manual attenuators for stereo returns of both AUX buses, as well as four gate inputs for automated clickless muting of each stereo input channel.
  • There is a passive breakout panel called Ustka planned, offering individual VCA outputs that may be used for multitrack recording.

Demos & Tutorials