Ostrawa 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.
Features
- 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
Expandability
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.
Ustka is a simple passive expander module that offers direct access to four pairs of stereo signals before they are combined into the mixed signal at the output of Ostrawa. Ustka’s main application is interfacing with external multichannel devices like computer audio interfaces and hardware multitrack recorders.
- 20HP wide
- 46mm deep (including the ribbon cable and bracket)
- Current draw: +180mA/-150mA
- Reverse power protection
How much is my shipping?
Shipping is automatically calculated before you submit your payment information. Simply add items to your cart and proceed to the checkout page, where you'll be offered shipping options and their prices. In the UK, 'next working day' shipping is free if the order value is over £150, and £5 otherwise. We can also ship on a 'next working day before 12pm' service, which costs £6 for orders over £150 and £7.50 for orders under £150.
Shipping to mainland EU typically costs between £7 and £20, depending on the shipping method and the size and weight of the order.
Do you ship to my country?
Almost certainly - the site will give you an estimate of shipping costs if you add an item to the cart and then enter your country and postcode. If you have specific requirements (such as if you prefer UPS over FedEx, for example) then let us know in advance and we'll try to work something out for you.
Shipping methods
We use a combination of DPD, Royal Mail and Parcelforce for the UK, and for international orders it's either DHL, FedEx, UPS, Royal Mail or Parcelforce depending on where you are in the world. If you have a particular preference then try to let us know BEFORE you order so we can look into it for you. Please note that there may occasionally be additional shipping charges if you live in a remote area, depending on what surcharges are applied by the shipper. We'll get in touch to discuss this with you in such cases.
Dispatch times
For UK orders, we aim to dispatch the same working day if we get the order before 16:00. If you have a really urgent situation then of course drop us an email before ordering and we'll always do our absolute best to accommodate you.
For international orders, we normally dispatch the same day if we get the order before 13:00 but again, occasionally it might be the next day before we can send it out, and sometimes the couriers may come to collect a little earlier than scheduled which would also push an order into the next day.
Saturday/Sunday shipping
If you're in the UK and you order before 16:00 on a Friday then we can send something for a Saturday or Sunday delivery with DPD. This is FREE for order values over £350, £5 for order values between £75 and £250, and £7 for order values under £75. (NB: this applies to UK mainland addresses only). Please note that any orders placed after 16:00 on a Friday will ship on the Monday.
International shipping times
Since April 2020, the couriers we use have suspended guarantees for shipping times, so even though we're paying them for priority services - 24-48 hours for most of the world - in practice it's often an extra day on top and sometimes it can be longer. There is absolutely nothing we can do about this, unfortunately. If you are outside the UK and it's a life-or-death situation where you absolutely MUST have that passive mult for the next day then... it may be better to find a local supplier.
Pre-orders
If a product is listed as a pre-order, it means we've ordered it from the supplier but it's not physically in stock yet. The product listing will include an estimated shipping date based on the best information we have from the supplier, but do bear in mind this is subject to change and is not a guaranteed date.
If you place an order containing a mixture of in-stock and pre-order items, we'll normally hold off on shipping anything until the pre-order item(s) have arrived, rather than splitting it into multiple shipments. If you need the in-stock items sooner, we'd recommend placing separate orders. As always, please get in touch if you have questions.
Product Overview
Ostrawa 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.
Features
- 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
Expandability
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.
Ustka is a simple passive expander module that offers direct access to four pairs of stereo signals before they are combined into the mixed signal at the output of Ostrawa. Ustka’s main application is interfacing with external multichannel devices like computer audio interfaces and hardware multitrack recorders.
Technical Specs
Shipping Details
How much is my shipping?
Shipping is automatically calculated before you submit your payment information. Simply add items to your cart and proceed to the checkout page, where you'll be offered shipping options and their prices. In the UK, 'next working day' shipping is free if the order value is over £150, and £5 otherwise. We can also ship on a 'next working day before 12pm' service, which costs £6 for orders over £150 and £7.50 for orders under £150.
Shipping to mainland EU typically costs between £7 and £20, depending on the shipping method and the size and weight of the order.
Do you ship to my country?
Almost certainly - the site will give you an estimate of shipping costs if you add an item to the cart and then enter your country and postcode. If you have specific requirements (such as if you prefer UPS over FedEx, for example) then let us know in advance and we'll try to work something out for you.
Shipping methods
We use a combination of DPD, Royal Mail and Parcelforce for the UK, and for international orders it's either DHL, FedEx, UPS, Royal Mail or Parcelforce depending on where you are in the world. If you have a particular preference then try to let us know BEFORE you order so we can look into it for you. Please note that there may occasionally be additional shipping charges if you live in a remote area, depending on what surcharges are applied by the shipper. We'll get in touch to discuss this with you in such cases.
Dispatch times
For UK orders, we aim to dispatch the same working day if we get the order before 16:00. If you have a really urgent situation then of course drop us an email before ordering and we'll always do our absolute best to accommodate you.
For international orders, we normally dispatch the same day if we get the order before 13:00 but again, occasionally it might be the next day before we can send it out, and sometimes the couriers may come to collect a little earlier than scheduled which would also push an order into the next day.
Saturday/Sunday shipping
If you're in the UK and you order before 16:00 on a Friday then we can send something for a Saturday or Sunday delivery with DPD. This is FREE for order values over £350, £5 for order values between £75 and £250, and £7 for order values under £75. (NB: this applies to UK mainland addresses only). Please note that any orders placed after 16:00 on a Friday will ship on the Monday.
International shipping times
Since April 2020, the couriers we use have suspended guarantees for shipping times, so even though we're paying them for priority services - 24-48 hours for most of the world - in practice it's often an extra day on top and sometimes it can be longer. There is absolutely nothing we can do about this, unfortunately. If you are outside the UK and it's a life-or-death situation where you absolutely MUST have that passive mult for the next day then... it may be better to find a local supplier.
Pre-orders
If a product is listed as a pre-order, it means we've ordered it from the supplier but it's not physically in stock yet. The product listing will include an estimated shipping date based on the best information we have from the supplier, but do bear in mind this is subject to change and is not a guaranteed date.
If you place an order containing a mixture of in-stock and pre-order items, we'll normally hold off on shipping anything until the pre-order item(s) have arrived, rather than splitting it into multiple shipments. If you need the in-stock items sooner, we'd recommend placing separate orders. As always, please get in touch if you have questions.
