XAOC Devices - Sewastopol 2

Sewastopol contains a number of circuits for integrating external audio and to extract signals from them. Use it as an input and output interface with optional soft clipping, as a FX send & return for using external effect units with your modular, as a comparator and as envelope follower. Latter two functions can be used individually with other signals than the external audio.

Please note: The following text still descripes the first version of the Sewastopol. An updated description will be available soon!

On the "studio side" the input and output channels have conveniently 1/4" sockets and there are potentiometers for adjusting levels: input-wise there's a pre-amp and output-wise an attenautor. Overload LEDs for each channel help to find correct gain setting. A jumper on the back lets you activate soft clipping.

Sewastopol can be used for a number of functions:
Audio interface: the EXPORT section sends signals from the Eurorack to your studio and is used as an Out. IMPORT is the input section for injescting external audio into the modular system.

Effect adaptor Export is used as FX Send with attenuation and import is the FX Return with amplification.

Envelope follower: A cleanly working unit generating a CV that follows on the volume of the input. Two speed ranges to select from - fast for transients and slow for smooth voltages. In addition the "Env. Release" control allows for adjusting the decay which is very hand when you insert very percussive sounds into the follower. Then there's a "Low End Cut" which is a highpass filter with switchable cutoff frequency (33Hz, 3kHz, off) for removing energy-rich low frequencies. It makes the follower less sensitive to bass that usually dominates much softer percussive sounds, and improves the overall response to mixed music.
The module implements a novel bipolar peak detector whose output is held until a subsequent waveform peak arrives. This results in a stable, ripple-free output voltage for a input signal with constant amplitude.
The follower has an individual input which is normalized to the Import's input. A LED shows if the follower's voltage is below or above +8V

Comparator: It compares the input signal's amplitude with the value set with the "threshold" potentiometer; when the input is higher it generates a gate and a trigger. LEDs show activity.
To prevent arbitrary switching when signals fluctuate very close to the threshold has the Sewastopol has a jumper-selectable hysteresis. This activates slightly different thresholds for the rising and falling voltages.
The comparator has an individual input which is normalized to the evnelope follower output.