Rungler

In his 2017 clinics at Manchester University, Rob Hordijk discusses his module designs, including one titled Rungler. He begins by saying that he wanted a noise generator for his system, but one that provided some parameters for interaction, rather than a fixed, static noise source - inspired by the work of Dutch composer Jan Boerman whose work explored the continuum of spectral complexity.

On his blog, he wrote: "The rungler is basically a CMOS shift register clocked by one oscillator and receiving its data input from [another] oscillator. The output bits of the shift register are used as a binary code 'to do something with'. The bits are then fed into a DA converter. This DA level output voltage is fed back to the oscillator frequency control inputs. The output of the DA is the 'rungler CV signal'. To describe the rungler waveform in similar terms as like a sine wave or pulse wave I call it a 'stepped havoc wave'."

Essentially, this is a stepped pattern generator which is useful at any rate for various purposes.

Rob Hordijk's Rungler module

This is my block diagram for a Rungler - two oscillators feed an 8-bit digital shift register whose last 3 bits feed a digital-to-analog converter (also known as Parallel In; Serial Out topology).

The XOR (exclusive OR) creates looping patterns that interact with the incoming OSC 2 data stream, giving instability to the patterns, otherwise known as chaos.

Here's my diagram for how the shift register and DAC work in tandem to produce stepped voltages from digital (high or low) signals. The voltages aren't representative of Hordijk's original design - I'm using a simplified model for pedagogical purposes.

Notice how the comparator is comparing the incoming voltage to a fixed threshold and outputting a logic high (1V for simplicity here, but usually ~5V in practice)

Each successive "Bit" output is delayed by one clock pulse, like a "bucket brigade" passing either full or empty buckets, depending on the comparator's output.

In the Rungler, there is an 8-stage shift register with the last 3 stages feeding the DAC, which produces the stepped analog voltage. Here's a more in-depth description of an R2R DAC.

In dissipative chaotic or dynamical systems, there's a dissipating factor that prevents infinite buildup. In population dynamics, this is individual deaths; in ant colonies, this is evaporation rate; in memory, it's forgetting.

A shift register functions like a memory, passing states along in time. An R2R DAC functions as a dissipating factor (evaporation, forgetting, dying, etc.) whereby each successive time step after sampling exerts progressively less influence on the system. Think about it like a fading memory: seconds after an impactful event, thoughts about the event are strong and affect your behavior and internal state directly. As time passes, and you accumulate more experience, the impact of the memory lessens until eventually, it's possible to completely forget about it. Similarly studies show

Much of my first album uses the rungler from a Benjolin for modulation of various parameters. I've recently been exploring using it to produce interesting rhythms with Destiny+ Czochralski Cells, which uses LFOs and a demultiplexer to produce complex rhythmic relationships.

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