4ms SISM: Shifting Inverting Signal Mingler

The SISM is a 4-channel voltage manipulator that can scale, invert, attenuate, shift (dc offset), mix, split, and slice your CV and audio signals.

A plethora of red and blue LEDs (14) show exactly what each channel and output jack is doing: red = negative voltage, blue = positive.

Each channel is independent and has an input jack, output jack, a knob for attenuating/inverting (Scale), and a knob for applying positive or negative DC offset (Shift).

Four jacks on the bottom combine the four channels in different ways. Mix is a straight mix of all four shifted inputs, Switched Mix is a mix of all channels that have nothing plugged into the OUT jack, Positive Slice is the sum of all output voltages greater than zero volts, and Negative Slice is the sum of all negative voltages.

By Shifting some channels positive and some negative, the + Slice and - Slice jacks can be used as sub-mix outputs. Also, by running a slow triangle wave into one channel, the remaining channels can be made to "dirty pan" between the Slice jacks: the signals are half-wave rectified as they span between both outputs.

Channels 1+2 and 3+4 are normalized together on the input jacks, which is handy for splitting a signal into two or more altered forms. Jumpers on the back allow you to disable this normalization.

Each channel also has a jumper to make the Scale knob unipolar (no inverting, attenuate only). This is useful for mixing audio instead of CV. A breakout header allows for padding of the signal (useful for fine-tuning a precise voltage such as 1V/oct).

Input and Output headers for connecting to QCD, QPLFO, VCA Matrix, or other manufacturer's modules such as Toppobrillo Mixiplexer or Circuit Abbey Intermix.

Basic features

Four independent voltage processor channels, with four mix/mingle outputs

Each channel has:

Input jack

Scale knob (from inverted unity, to zero, to unity

Shift knob (adds/subtracts DC offset from -9V to +9V)

Output jack

Red and blue LEDs to indicate + or - voltage, as well as intensity

MIX jack outputs sum of all channels

MIX SWitch jack outputs sum of all channels with nothing plugged into their output jack

+ SLICE jack outputs positive portion of mix (voltages greater than 0V)

- SLICE jack outputs negative portion of mix (voltages less than 0V)

Red and blue LEDs on all four mix/mingle jacks display what the signal is doing

Advanced features

Channels 1+2 and 3+4 are normaled together on the input, so plugging into Channel 1 (or 3) will split the signal: A jumper can disable this normalization

Scale knob has three ranges that are selectable with jumpers:

Bi-polar: -1x to +1x (inverting unity to unity) --default

Uni-polar: 0 to +1x (level fader)

Boost: 0 to 2x (twice the voltage gain)

Input Header (2x4) for connecting the output of a QCD or QPLFO to the SISM's inputs. Plugging into the input jacks overrides the signal on the header

Output Header (2x4) for connecting to the input of a VCA Matrix or other compatible module

PAD breakout header (2x4) for connecting to a breakout module that applies a pre-set pad (attenuation) to each channel.

Usage

Attenuator (quad)

Inverter (quad)

Level shifter/DC offset (quad)

Mixer (4 inputs)

Splitter (dual 1->2, or single 1->4)

Voltage slicer: + and - portions of a signal are outputted independently to the SLICE jacks

"Dirty" panning: apply a large slow wave to one channel, and the other channels will "pan" between the SLICE jacks. The signals are half-wave rectified as they span both outputs

LFO mingler: connect QPLFO outputs to SISM inputs and have complete control over each channel as well as four different mix outputs

Sequencer: connect QCD outputs to SISM inputs (or any clock divider/multiplier) and take the sequencer output from the MIX jack.

Add attenuation and inversion to any CV jack on other modules

Keep all your fine-tuning controls for CV inputs on several modules in one place

Module size The SISM is 12HP and 0.86 inches (22mm) deep.

Power consumption

+12V rail: 51mA max -12V rail: 51mA max