The Slightly Nasty Model 2241 Voltage Processor is a useful control voltage and signal processor that combines a handful of commonly-used functions into a single panel. It includes four attenuverter units, two 3:1 mixers, two static voltage sources, two voltage comparators, and a level conversion unit.
Each of the attenuverters can either be used in isolation via their own outputs, or as part of a mixer stage that takes two attenuverters (A and B) and one unscaled direct input (C) and sums them together at the A+B+C output, along with a useful bicolour LED level indicator showing the output voltage. The B attenuverter input can also be switched between the B IN jack and an internal regulated +5v source, allowing it to be used as a static voltage source, or as an offset for signals going through the mixer section.
The C input is intended mainly for when pitch CV signals need to have other signals added to them, such as an LFO vibrato for example. It is important to maintain the scaling of these signals to avoid pitch tracking errors, and so the C input allows these signals to pass through to the output accurately.
The comparator of each stage compares the post-attenuverter input signals from A and B and outputs a “high” (+5v) logic signal if A is greater than B, or a “low” (0v) signal if the reverse is true. These logic outputs are diode-coupled to allow for wired-OR operation if desired – meaning that they can be connected with other diode-coupled logic outputs to feed a single logic input within a patch.
The bottom of the panel features a simple level converter that allows bipolar (+/-5v) and unipolar signals (0-5v) to be easily converted from one to the other. This can be useful when things such as feeding a bipolar LFO signal from a module like the 2231 Asymmetric Slew Limiter to a VCA with a unipolar GAIN input, or when using the envelope mode on a 2231 to do subharmonic generation, where the output will be a 0-5v signal.
UPDATES: Documentation updated 28/3/2022 – fixed BOMs, which had not been correctly updated from last prototype revision. Missing capacitor values added and switch type corrected. C105 changed to 10uF, but can be left as 100uF if already soldered.
v1.0 PCB – Current Documentation (v1.0 Rev A) :