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Modular Diary – 073

“A chaotic signal is not a random signal.” I got round to taking a look at Rob Hordijk’s recent Rungler Demo at Modular Meets Leeds 2017, a nice complement to the Mallorca demonstration from 2012.

One detail that I found very interesting was his demonstration of the patterns that can appear within a chaotic signal – the bifurcations or period doublings that can create harmonic partials that are lower in frequency than the signal fed into the filter.1 I’d noticed something like this in James Cigler’s TwinPeak demo yesterday, and had some fun trying it out myself with the filters in my Audulus Blippoo patch.

In essence, since a filter is a feedback system, the moment you apply non-linear feedback, the system automatically becomes potentially chaotic.

I also managed to implement a sample & hold in the Blippoo patch. Hordijk’s inclusion of a S&H in the design is interesting since the Rungler modulations already have something of a S&H character. I take it that including it had something to do with his observation that frequency modulation has a stronger effect when the modulating signal is lower in frequency than the one it is modulating. Using a S&H provided him with a useful device for effectively modulating low frequency periods such as envelopes, for example. In the Blippoo context the S&H definitely seems to add to the chaotic character of the patch rather than simply adding an extra FM modulation band when the modulating oscillator is higher in frequency.


  1. Hans Timmen refers to this on his website: “By using a nonlinear feedback system, patterns are created that exhibit chaotic properties like attractors, bifurcations, etc. Second, the filter also uses a nonlinear feedback system that can go into ranges where bifurcations occur, which results in the creation of ‘undertones’, where the period doublings create harmonic partials that are lower in frequency than the signal fed into the filter.” — Rob Hordijk 

Modular Diary – 072

I made a little more progress on my Audulus Blippoo today, with a pulse-width signal generated from a comparator between the two oscillators and, perhaps most importantly, a form of Twinpeak filter.

Once again I found it very useful to take a look at James Cigler’s demo and overview of the Epoch Modular TwinPeak (despite its somewhat shaky start).

The filter adds a lot of character to the chaotic core of the Blippoo, and its ingenious (again cross-modulating) design makes it a lot of fun to play with. I can imagine it being well worthwhile putting together a standalone version of it for use in other contexts.

A standalone Audulus (µ)module would require a little more thought into how the controls are linked up and presented – for the moment I’ve simply kept everything loosely connected since I’m still in a process of learning and discovering how the different parts affect the whole.

The next step is to implement the sample and hold.

Modular Diary – 071

With the Hordijk Putney-Revox patch in place I spent some time taking a fresh look at the schematics of the Blippoo, Benjolin, and Rungler circuits, slowly getting to know them a little better and understand the differences between them.

I also found James Cigler’s video tutorial on the Epoch Modular Benjolin useful in that it starts with a demonstration of the most straightforward aspects of the module before diving into the more chaotic modulations it is know for.

With that in mind I went back to my Putney-Revox patch, replacing the delays with Robert Syrett’s µRungler and starting to fill in the other connections. It’s a small beginning, I still need to add the S&H and comparator, and take a look at what could be done with the filter, but it’s fun to learn about what’s possible with the few elements that are in place, each step of the way.

Modular Diary – 070

I thought it would be fun to go back to the beginning and make an Audulus patch of the Putney-Revox setup that initially got Rob Hordijk going with his Blippoo/Benjolin/Rungler circuits.

I remembered that Robert Syrett had put together a VCS3 inspired oscillator a while back and thought that I’d use that as a point of departure. My first tryout is the basic setup with two oscillators and two delays. It’s fascinating how much one can get out of such a simple patch, especially when bringing the waveshaping into play.

I made a second version with a square wave on the second oscillator so as to get a little closer to the differences between the two VCS3 oscillators, also spending a some time with the iVCS3 app taking a look and listen to what exactly is going on with them.

A next step could have been to try and recreate the VCS3 oscillators more accurately, but then I noticed Robert Syrett’s recent µWaveBender and thought I’d try out a quick version with the (anti-aliased) Audulus node oscillators and the µWaveBender. The principles of the original in an updated form.

Modular Diary – 60

The Rob Hordijk Benjolin Workshop video that I’ve referred to in recent posts also helps clarify the lineage of the Rungler and his Blippoo/Benjolin ‘patches in a box’. At the end of the video he explains how it was the Blippoo Box that was an attempt to most closely recreate the Revox–Putney (VSC3) cross-modulation setup:

…in the analog modular system there’s also a Rungler module that actually has five different modes and there’s different sort of things because you can make all sorts of variations on this shift register idea… this [the Benjolin] is basically the simplest that you can get, it is basically also just one delay, actually when I built the Blippoo Box before this one, the Blippoo Box has two shift registers because that was really sort of a copy of that Putney Revox idea, but for the Benjolin I thought well if I can do it with one chip and and the amount of op amps and transistors and the potmeters on the board and you should be able to build it in an afternoon, …let’s try to do the simplest and most interesting thing.

One thing that comes across in this and other of Rob Hordijk’s workshops is his enthusiasm for the elegance of a particular cicuit. How a simple setup can open up for a rich palette of results. The impetus for the form of his cicuits is often closely tied to their analogue implementions, and many of those forming factors may no longer binding when creating digital versions, beautiful as they may be.

Modular Diary – 057

Thinking further on the difference between analogue circuits and digital implementations of them, and how experiments in one form of technology can be carried over into another, I found it fascinating to hear Rob Hordijk tell a little about the origins of the Blippoo/Benjolin type circuits in a video that I hadn’t come across before:

…around the year 1980 we had these EMS Putney synthesizers and we had these Revox R-77 tape recorders and with with the Putney synthesizer you could make a really nice, always changing patch, by routing, by using two of the oscillators of the Putney and using the Revox as a delay, because the Revox had three heads, a recording head and a playback head and you could record and a little while later on the playback heads you could get a signal back and because it had two tracks you could make two delays, so what you would do you would feed the output of one oscillator in the left input of the of the tape deck, then the output of that left channel on the tape deck would go into the frequency modulation input of the second oscillator, the output of the second oscillator would go into the second track of the of the Revox and the output of the second track of the Revox would go back into the frequency modulation of the first oscillator, so you would have a cross modulation system and the Revox would introduce some time delay, so the cross feedback would be delayed, and this delay sort of makes the system completely chaotic and totally unpredictable and it could just go on for hours and constantly do different things, so I remembered that and I thought that is something interesting to do in the Benjolin…

Modular Diary – 056

A little side-note on the Turing/Quantussy/Rungler Audulus implementations: Something that I did notice while playing around with STS’s Copier and Turing Machine was that patches would open in exactly the same state as last, something that Richard Brewster also draws attention to in the post on his Audulus Quantussy.

One very interesting feature of an Audulus patch is that it will start off playing in the exact state in which it was saved. So, very much unlike the analog Quantussy, I think that the sequence of events created by the software Quantussy may be able to repeat exactly.

Following on that, Rob Hordijk’s thoughts on the differences between digital and analogue implementations of these kinds of cicuits:

Imho a rungler circuit works best in an analog electronics implementation. It is definitively more alive and surprising due to the slight instabilities in the analog circuitry. I did digital implementations, but they can’t beat the ‘organic behaviour’ of the analog versions. But this is just personal taste…

Modular Diary – 055

The Din Datin Dudero – ‘the original, esoteric analog synth for babies’ – something that caught my eye amongst all the unusual on the Ciat Lonbarde site. There’s also the Nobsrine:

It is for babies of DJs and noise musicians, who want to introduce their children to strange sounds, chaos magic, the idea of infinite degrees of relationship between tones, without the more complicated techniques involved in uper crust CIAT INSTRUMENTS.

I was wondering about the relationship between all these instruments and Rob Hordijk’s ‘patches in a box’, and sure enough, looking though the images for the Din Datin Dudero I stumble across:

Stuber shall have two knobs, a philter mechanism for audio and also for gesture, with Q control. The binary matrix reinterprets resonances, as a “Rungler.”

Here’s a video of their creator Peter B. explaining his Plumbutter.

Modular Diary – 054

After yesterday’s look at the striking Ciat-Lonbarde instruments, I got to thinking of Rob Hordijk’s Benjolin and Blippoo boxes, and specifically a comment of his about their potential status as objets d’art:

…a little device called the Blippoo box, and that type of instrument I always call a ‘patch in a box’ because it is sort of like a concoction of certain electronics that have a certain specific character of its own, …it should be playable of course, it can also be seen as maybe an objet d’art, what the French call an objet d’art, an ‘object of art’, instead of an instrument, but that is basically free for the people that have one to interpret whether you want to use it as an actual musical instrument on stage, or if you just want to have it in your room as something special next to your paintings and your other stuff…
—Rob Hordijk at Basic Electricity #15, Berlin

Modular Diary – 053

While playing around creating drone-like textures with STS’s Turing Machine, I got to thinking of Pugix’s Audulus Quantussy drones that I came across in the forum a few weeks ago. He has a nice post on his website explaining it all along with some sound examples.

I was curious to take a look at the hardware Quantussy (What is the Quantussy?) that provided the inspiration for Richard’s version, and that led me to some of the most unusual modules I’ve yet come across. As described on the website:

Ciat-Lonbarde specializes in intuitive analog organs for your atonal/chaos squishing needs. The following instruments are assembled in Baltimore out of local wood, and machine assembled circuit-boards that are hazmat free.

The circuit boards are works of art in themselves. Here’s a Reddit Inquiry into the artsy-hipster side of Synthesis, and an ilovefuzz.com thread with a number of videos of these instruments in action.