vostok-instruments-sigma

Vostok Instruments Sigma

Hybrid rhythm computer

12 HP Eurorack module

Sigma is a four-channel gate-length processor for rhythm and timed-event manipulation. It produces adjustable copies and inversions of incoming pulses, then derives new gates from adjacent processed channel pairs with analog Boolean logic.

Features

  • Generates up to 23 simultaneous gate signals from four gate inputs.
  • Four CV-controlled processors create copies of incoming pulse signals with lengths adjustable from 1 ms to indefinite sustain.
  • Each LGTH CV input is summed with its channel's knob setting; negative voltage reduces the resulting length.
  • If negative length CV exceeds the current manual setting, the channel stays at minimum length until its CV input rises above zero.
  • When pulses arrive faster than the selected length, the main output drops low for 200 microseconds and immediately returns high rather than ignoring the new pulse.
  • Each adjacent channel pair provides analog AND, NAND, OR, NOR, and XOR results, and every channel has a dedicated NOT output.
  • A channel's NOT output inverts the processed main output and can function as a length- and CV-controlled gate delay.
  • Remember: At very high length settings, some destination gate inputs may miss hits; reduce the applicable LGTH setting until the destination responds correctly.
  • Remember: Turn the Eurorack case off before installing or removing Sigma, and orient the power cable's red stripe to -12 V at both ends.

Controls & Jacks (39)

  • Channel 3 LGTH— Sets Channel 3's processed gate length from 1 millisecond to 10 seconds, with external length CV summed with this setting.
  • Channel 2 LGTH— Sets Channel 2's processed gate length from 1 millisecond to 10 seconds, with external length CV summed with this setting.
  • Channel 1 LGTH— Sets Channel 1's processed gate length from 1 millisecond to 10 seconds, with external length CV summed with this setting.
  • Channel 4 LGTH— Sets Channel 4's processed gate length from 1 millisecond to 10 seconds, with external length CV summed with this setting.
  • Channel 1 Gate Input— Receives the pulse signal processed by Channel 1.
  • Channels 1-2 XOR Output— Goes high while the processed outputs of Channels 1 and 2 differ.
  • Channels 3-4 OR Output— Goes high while either processed output of Channels 3 and 4 is high.
  • Channels 3-4 NOR Output— Goes high only while the processed outputs of Channels 3 and 4 are both low.
  • Channels 2-3 XOR Output— Goes high while the processed outputs of Channels 2 and 3 differ.
  • Channels 2-3 NOR Output— Goes high only while the processed outputs of Channels 2 and 3 are both low.
  • Channel 3 NOT Output— Outputs the logical inversion of Channel 3's length-processed main output and can consequently act as a length-controlled gate delay.
  • Channel 3 LGTH CV Input— Adds an external voltage to Channel 3's manual length setting; negative voltage reduces the resulting gate length.
  • Channels 1-2 NOR Output— Goes high only while the processed outputs of Channels 1 and 2 are both low.
  • Channel 4 OUT— Outputs a 5 V copy of Channel 4's incoming pulse with its length adjusted from 1 ms to 10 seconds or held indefinitely in Infinite mode.
  • Channels 3-4 XOR Output— Goes high while the processed outputs of Channels 3 and 4 differ.
  • Channel 4 NOT Output— Outputs the logical inversion of Channel 4's length-processed main output and can consequently act as a length-controlled gate delay.
  • Channels 1-2 OR Output— Goes high while either processed output of Channels 1 and 2 is high.
  • Channels 2-3 NAND Output— Stays high except while the processed outputs of Channels 2 and 3 are both high.
  • Channel 2 LGTH CV Input— Adds an external voltage to Channel 2's manual length setting; negative voltage reduces the resulting gate length.
  • Channels 3-4 AND Output— Goes high only while the processed outputs of Channels 3 and 4 are both high.
  • Channel 3 OUT— Outputs a 5 V copy of Channel 3's incoming pulse with its length adjusted from 1 ms to 10 seconds or held indefinitely in Infinite mode.
  • Channel 2 OUT— Outputs a 5 V copy of Channel 2's incoming pulse with its length adjusted from 1 ms to 10 seconds or held indefinitely in Infinite mode.
  • Channel 2 NOT Output— Outputs the logical inversion of Channel 2's length-processed main output and can consequently act as a length-controlled gate delay.
  • Channels 3-4 NAND Output— Stays high except while the processed outputs of Channels 3 and 4 are both high.
  • Channel 1 NOT Output— Outputs the logical inversion of Channel 1's length-processed main output and can consequently act as a length-controlled gate delay.
  • Channels 1-2 AND Output— Goes high only while the processed outputs of Channels 1 and 2 are both high.
  • Channels 2-3 OR Output— Goes high while either processed output of Channels 2 and 3 is high.
  • Channel 2 Gate Input— Receives the pulse signal processed by Channel 2.
  • Channel 1 LGTH CV Input— Adds an external voltage to Channel 1's manual length setting; negative voltage reduces the resulting gate length.
  • Channels 2-3 AND Output— Goes high only while the processed outputs of Channels 2 and 3 are both high.
  • Channel 4 LGTH CV Input— Adds an external voltage to Channel 4's manual length setting; negative voltage reduces the resulting gate length.
  • Channel 1 OUT— Outputs a 5 V copy of Channel 1's incoming pulse with its length adjusted from 1 ms to 10 seconds or held indefinitely in Infinite mode.
  • Channel 4 Gate Input— Receives the pulse signal processed by Channel 4.
  • Channels 1-2 NAND Output— Stays high except while the processed outputs of Channels 1 and 2 are both high.
  • Channel 3 Gate Input— Receives the pulse signal processed by Channel 3.
  • Channel 1 Output Signal— Indicates the state of Channel 1's length-processed output signal.
  • Channel 2 Output Signal— Indicates the state of Channel 2's length-processed output signal.
  • Channel 3 Output Signal— Indicates the state of Channel 3's length-processed output signal.
  • Channel 4 Output Signal— Indicates the state of Channel 4's length-processed output signal.

How-To Guides

  • Create a length-shaped logic rhythm
  • Create a gate delay
  • Sustain a gate indefinitely

Explore the interactive Sigma panel on BleepDex — tap any control to learn what it does.

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