Benjolin patch for VCV - Show me what you can do with it!

In 2009, Rob Hordijk designed a “primitive” synth instrument called the Benjolin and released the design to the world for DIY enthusiasts, as well as developed a kit and conducted many workshops. It consists of two oscillators, a multimode state variable filter, and a pseudo random circuit called the rungler. It is a shift register sample and hold using oscillator 2 pulse as the clock, and oscillator 1 triangle through a comparator, XORed with the end of the shift register as the data input. Three of the shift register values are treated as binary bits and converted to analog voltages with 8 possible values, which is the primary output of the rungler. Another comparator uses the triangle waves from both oscillators to create variable width pulse waves that are fed as input to the filter.

The magic comes with multiple cross modulation paths, and knobs to attenuate the various signals. The deceptively simple design can create an endless variety of sounds with a few twists of the knobs - with lots of auto generative possibilities. Nothing is truly random, but there is chaos galore. A complete self contained experimental electronics instrument in a box.

Since then there have been various enhancements, as well as adaptations to create Eurorack Benjolin modules. After Later Audio collaborated with Rob Hordijk to create the Benjolin V2 Eurorack module. It has all of the original components, with some really useful enhancements, as well as a patch bay. It still works wonderfully as a standalone instrument, but also integrates well with larger modular rigs. Here are a couple nice demonstration videos.

I have studied the extensive user manual, and I believe I have fairly accurately replicated the functionality of the Benjolin V2 as a VCV patch using free modules.

Note - There is a newer version (more compact and lighter CPU usage) in a later post below

I have already spent hours exploring the sound possibilities with this instrument. It is so easy to get lost in this world. I haven’t even begun to explore what is possible by incorporating the instrument into a larger patch, other than incorporating some reverb.

Here is one chill recording that I created that is mostly auto-generative, with only a few tweaks strategically placed throughout the 12 minute piece.

Now I encourage others to try out the patch and see what you can do with it. And please, please, please - post your results to this topic. Try it as a standalone instrument as I have done, or show me what you can create using the patch bay and additional modules. Just don’t make any modifications to the benjolin itself - all of the intended user controls and patch bay inputs/outputs are clearly labeled.

If you are unable or unwilling to share a recording or video, at least post a response describing your experience with the patch. I would love to hear some feedback. Or if anyone owns the actual hardware, tell me how close the emulator is to the real thing, and maybe make suggestions for improvements if I got any of the design wrong.

I have never had the opportunity to work with any Eurorack hardware. If I ever invest in my own hardware system, I am pretty sure I will include the After Later Audio Benjolin V2. For those that already have a Eurorack system, maybe playing with this patch may convince you to purchase the module.


Dave, I don’t have anything to show you (yet), but I wanted to thank you for sharing this. I’ve spent a couple of hours playing around with it, and enjoy the unusual sounds it can produce.


I look forward to hearing some of your discoveries!

Hello @DaveVenom, thanks for the opportunity. I just downloaded the patch. I look forward to exploring, experimenting, creating. I will let you know, what I come up with . . .

Here is a fully autogenerative patch derived from my Benjolin emulator.


So, after a lot of fun with a lot of noise, finally something musical emerged, presumably a soundtrack of a soviet 1970ies cartoon “Литтле Ред Ридинг Хоод”


Musical indeed - I love it!

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I realized I could shrink the Benjolin patch down and improve CPU usage by using 2 VCV Fundamental LFOs instead of the 4 Nysthi oscillators. I don’t notice any qualitative difference in the output after making the change.

Then I stumbled on a configuration that sounds remarkably like an irritating avant-garde jazz sax solo.


Love the benjolin. Here’s a screenshot of my take on a simple benjolin patch. HetrickCV rungler makes this very, very easy to setup… (Here’s Hetrick’s description of the module (somehow it’s not in the vcv manual): Rungler | Cherry Audio Store)

I went for the bog VCO because the slow switch makes it easy to go down to lfo rates (which we want for slower, more melodic rungler behavior), but can also just be a vco if you want to explore the noisy mess side of the patch.

I went for Freak as my filter because I just love Vult filters.

I also really like this overview of benjolin inspired patch strategies by Eric Schlappi:

Edit: here is my patch. I added 2 vco variations (bog vco & tides) because it’s fun! (Tides is so nice in this patch! It also allows us to make the patch stereo.) Benjolin Variations | Patchstorage

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I downloaded your Benjolin patch, and it’s silent until you put an effect in the host-fx right before the master recorder. FYI. Took me a minute to work that out.

Sorry for being stupid but where are the Stoermelder-P1 modules from?

There are links scattered in many places in this forum. But I included a link for the Stoermelder modules at the bottom of my PatchStorage post in the original post from this topic - the same place where you can get my original patch.

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Got it. Thanks!

Great! Ben’s collection of modules is amazing, and there is a horde of people eagerly awaiting the official release for Rack version 2. But thankfully we can still use them early if we are willing to use a plugin that has not been fully tested.

I can’t imagine building my benjolin without them. The uINFIX and INFIX make it really easy to create a clean patch bay with inputs that have normaled connections. I could have used other means, though perhaps not as elegantly.

But even more important is the GLUE that provides beautiful labels. I spent a long time arranging and labeling so the user interface is in two places (controls upper left, patch bay upper right), and avoided cables that cover any of the controls or inputs. The ability to place labels directly on any module is really a game changer. It really facilitates a clear, easy to use and understandle UI.

There is soooo. much more in his collection. One of my favorites is TRANSIT, which lets you take snapshots of parameters scattered throughout your patch, and beautifully morph between settings upon demand.


Definitely a simplified version, but I imagine it still demonstrates some chaos nicely.

My goal was to emulate all the functionality from the After Later Audio version.

Thanks for the manual reference. I found that module, but dismissed it out of hand for my benjolin because I didn’t want to take the time to figure out how it worked, and I knew how to build one from other modules.

But now that I have seen the manual (and also did some testing), there is a critical difference between the Hetrick module and the original rungler design (and all variants since then).

The true rungler input is an XOR of the last stage of the shift register with the external input. This is an important aspect of the pseudo random data that it creates. The original simply took the pulse from oscillator 1 and XORed with the exiting shift register value. Later versions provided a switch to use the osc1 pulse, constant 0, or constant 10. The osc1 input creates pseudo random values, the 0 input loops the 8 steps, and the 1 input loops the steps, but alternates between original values and inverted values (16 steps instead of 8). The final version that is used in most implementations I have seen, including the ALA module that I emulated, is to switch to using the OSC2 triangle fed into a comparator with a variable threshold, and then XOR that result with the exiting shift register value. The two comparator extremes replicate the 0 and 1 options, and everything in between gives varying degrees of probability of looping, or using a pseudo random value.

The Hetrick “rungler” uses the comparator, but fails to implement the XOR.

Count Modula has a nearly identical module from a functionality standpoint - the Gated Comparator, which is an emulator of a CGS module made by Ken Stones

The gated comparator uses OR instead of XOR, which is still a major difference. A nice feature is it lets you choose which bits are used by the DAC. But it is striking how similar the gated comparator is to the rungler.

As far as I can tell from reading various sources, both Rob’s rungler and Ken’s gated comparator were developed in the 80’s. I’m curious who was influenced by whom? Or did they both happen to dream up the same basic design at roughly the same time?

The benjolin oscillators span between 18 and 19 octaves. I chose the Nysthi LFO, (and later the VCV Fundamental LFO) because they each can cover that range continuously to better emulate the hardware. I think I tested Bogaudio, and it could not cover the full range without switching. The benjolin is designed to go from 45 seconds per pulse, to about 8kHz.

I also intentionally set the FM attenuation at ~.93 because the benjolin is supposed to not quite track 1V/Octave.

Absoultely - Vault filters are amazing! It looks like you used the Steiner Parker mode. I chose the Unstabile module because the benjolin is designed to use a 2 pole state variable filter. I also tried Sabile, but got better results with the former.

I spent some time calibrating the resonance control so that it would not self oscillate unless you feed back the BP filter output into the external input, as described in the hardware manual. The Unstabile creates some gorgeous pings.

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I remember when you were making a Subharmonicon and I asked why you didn’t use mine. The answer was that mine didn’t allow the two sides to be used independently. I had never heard that before. Perhaps when you find these things you could log an issue or ask if it’s intentional? I’ll bet that would be useful to some people

I did check the CGS documentation for the actual hardware, and indeed Adam’s module appears to be a faithful emulation that uses OR.

I also put a feature request into the CountModula github a few days ago, asking for XOR as a context menu option!

oh, cool. Those devs are lucky to get your input.

Yeah - I did not document that version quite as well as some of the others. Glad you got it working.

As I tersely mentioned in the PatchStorage post, the effect I used is the free Valhalla SuperMassive, with the Dark Horse preset (preset found under SFX/Nebulae)

WooHoo! - Adam just replied on github that he implemented the enhancement for the next release!

That can certainly simplify my benjolin emulator :smiley: