I thought rungler was exclusive to Benjolin (as in, not a generic element existing beyond that context). Looking it up, it seems as though that is correct. Moreover it is quite a specific thing and any other instances would presumably follow the same design. You could extend it by using longer shift registers (different IC or chaining), or put more bits into the DAC, but my suspicion is other versions will be basically the same circuit.
Specifically, it looks like a hysteretic comparator (with an extra feedback element) feeding a regular 8 step shift register. That has an external clock input and the last 3 stages feed a standard resistor ladder+opamp summer D to A. It has a fixed feedback from the final output to the input which sums with the input. In benjolin it’s fed from the output of oscillator 1, with a switch to add in an offset voltage from a pot. The second oscillator’s output clocks the shift register. To use it without these two elements you therefore need to add a clock source (intended to be audio rate, e.g a square wave VCO, perhaps a Schmidt register+pot or V/Oct tracking one) to replace the input from oscillator 2 (clock) or an external input, through a comparator with an adjustable reference voltage, to allow you to turn arbitrary audio rate signals into squares (hysteretic would be an asset). The oscillator one input could be a jack (similar to the clock I described), driven be another internal oscillator, or by a switchable noise source.
I guess my observation is the “rungler” in itself is quite simple, but how you’d build a module around it depends on what you want it to do. Benjolin is the canonical example but it would be fairly easy to come up with many variations on that theme. I suspect breadboarding it and trying out several configurations would be the best way to find a design that feels useful. In particular, conceiving of them in the abstract, given the core of the circuit, it’s quite hard to visualise (or audiate) the result.
