Eurorack Quantussy Cells

This diagram shows a generic quantussy cell, as I call it. See What Is The Quantussy for more information. It’s the name of the five oscillator cluster in Peter Blasser’s Cocoquantus. My Quantisise is based on it.

Generic Quantussy Cell

A quantussy cell can be made from any LFO that has both pulse and angular outputs, plus a pair of sample and holds. The LFO clocks both sample and holds and also outputs an angular wave form, either a ramp or a triangle. One of the sample and holds is labeled ‘Castle’, the name taken from the corresponding output on the real quantussy.  Its input and output are patchable. The other sample and hold samples a control voltage that is internally applied to the frequency modulation input of the LFO.  The colors red, gray, violet, and green correspond to the jack colors I used on the Quantisise and serve as a shorthand way of referring to the two inputs and two outputs of a quantussy cell.

A few Eurorack Implementations

 

Tromsø Quantussy Cell

Tromsø is a Bastl Instruments module containing a VCO/LFO, a comparator, and a sample and hold.  Adding another external sample and hold, such as one from a 2hp Dual Sample & Hold, creates a quantussy cell.  The internal S&H samples a CV, which is routed to the FM input of the LFO.  The triangle of the LFO is the main output.  The 2hp S&H serves as the Castle.

 

Disting plus Slew Quantussy Cell

This implementation uses the Dual S&H from a Disting.  A single gate/trigger samples each of two inputs to two outputs.  It’s perfect for this.  For the LFO here I can use a Make Noise Function (or half a Maths) or a Mini Slew.  EOC is used to trigger the dual S&H.  One S&H samples a CV, which is applied to the Rise CV input.  (Fall CV or Both CV could be used.)  The slew output is the main out.  The second S&H is the castle.

 

Twin Waves LFO plus URA Quantussy Cell

This interesting variation uses the Ultra Random Analog Dual S&H module for both sample and holds, plus the clock.  The internal clock (a square wave) clocks both sample and holds.  One of them samples the CV and routes it to the clock FM input.  The second S&H is the Castle.  For the angular wave we use an LFO from Klavis Twin Waves in external sync mode, which turns it into a tap tempo LFO.  The LFO will try to match the rate of the pulses on the sync input.  The LFO output is the cell output.  Any angular wave form can be selected, but often a ramp wave is more useful.

The Ring

Quantussy cells may be patched together in many topologies.  The two inputs of each cell must come from the two outputs of another.  The main out is patched to the Castle input and the Castle out is patched to the CV input.  This results in the FM of the cell being taken from the Castle output of another.  Since it is sampled again internally, Peter calls this re-castling.  In the real quantussy, each of the five cells has a two pole, four way selector switch allowing it to be controlled by any of the other four cells.  In a modular application, we use patch cords.  I’ve found that the most effective way to compose cells is to arrange them into a ring of an odd number of cells.  Quantussy offers a maximum of five in a ring, but you can patch as many as you have hardware for.  I made a patch of seven.

Seven cell ring

All the way round we patch Red to Violet and Green to Gray.  The outputs from this ring are the Main (green) and Castle (red) outputs, which in addition to controlling the next cell in the ring can be used to control anything in your modular.  From the main outputs you get sloped waves, useful as envelopes for VCA, filter cutoff, etc..  From the Castle outputs you get stepped waves useful for oscillator pitch, etc..  While you could use the CV S&H output and/or the LFO pulse output in your patches, I invite you to look at these as internal to the cell.  This will simplify an already complex structure.

Example

Ring of Seven Quantussy Cells in Eurorack

That’s what a ring patch looks like, before taking outputs from it to control other stuff.  By using stack cables, it’s easy to tap the outputs.  A fun thing is to try different orders of the different cell types when patching up the ring.  I made the following recording using some of the outputs to control various parameters of the Loquelic Iteritas VCO and also to control the level.  This is a single voice.  Imagine what you could do with multiple voices!

 

An earlier example shows where I used four Tromsøs plus the Sport Modulator in a ring of five.

Once you have a ring of quantussy cells, it’s wide open what you can do with it to automate generative patches.  Tuning of initial parameters for rates, frequencies, modulation depths, etc., is essential to obtaining a more musical result.  Nothing ever repeats exactly in this kind of patch, even from one moment to the next.  But there is enough self-similarity to create a character.

For a lot more example of this technique, not necessarily using Eurorack, please visit the Quantisise tag.

 

Share

Leave a Reply

Please use your real name instead of you company name or keyword spam.