September 07, 2018

The Rungler

The purpose of the rungler is to create short stepped patterns of variable length and speed. One could categorize the circuit somewhere halfway between a plain S&H and a shiftregister-based pseudorandom generator. It needs two frequency sources to work and basically creates a complex interference pattern that can be fed back into the frequency parameters of the driving oscillators to create an unlimited amount of havoc.

The rungler is basically a CMOS shift register clocked by one oscillator and receiving its data input from the other oscillator. The output bits of the shiftregister 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'.

When the rungler signal is fed back to the frequency parameters of the oscillators it will change the triangle waveforms and pulse widths of the oscillator outputs, making other types of havoc waves, like a 'pulsed havoc wave' and a 'sloped havoc wave'.

The rungler will try to find a balanced state. In this way it behaves according to principle from Chaos Theory. There seems to be an unlimited amount of possible balanced states and when a balanced state is just slightly disturbed it can be noted that it takes a little time to find the next balanced state, with noticeable bifurcations, etc. Note that a new balanced state is defined by the exact position of the control knobs plus the previous state it was in.

The two wide range oscillators (not compliant to the 1V/Oct standard response) can cross-modulate and/or can be modulated by external signals. Oscillator A produces a Sine wave and provides clocking for the shift register. It has fluct modulation with rate controlled by Osc B Rate. As Osc B can go in audio range, fluct can cause sort of soft sync effect. Oscillator B produces a Triangle wave and provides the material for the shift register. Oscillators A & B are available as direct outputs. The output of the shift register can be applied to oscillator A in Stepped, Smoothed and Pulsed modes simultaneously. These Stepped, Smoothed and Pulsed signals are also available as direct outputs. Smoothed and pulsed are derived from stepped signal. Smoothed is sort of filtered stepped signal. Pulsed has 2 states : On and Off.

Clock In & Out makes syncing to other modules possible.

The Rungler has different operational modes that can be selected with a switch.

Random - Constant change when VCO B is lower freq VCO A, locked when higher. At audio rate, if Osc B is tuned higher than Osc A there is a sort of noise pattern but that’s loop quicker than the normal digital noise. By lowering VCO B Rate there is noise & every time you increase it, it has different kind of timbre.

Sparse - VCO A Rate can be very slow, can have sort of stepped signal. When modulating pitch, you have a short sequence of 32 notes. VCO B is locked when higher than VCO B.

Dense - Chaos increases with VCO B frequency. It never locks.

Here is the flowchart of the Rungler :

Check these videos for sounds and more explanations :

I wasn't able to upload the video of the Rungler at Novars Workshop so here's the link :

Thanks to Todd Barton who provided the picture of the module.

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