Turing Machine Random Looping Sequencer Documentation

The Random Looping Sequencer is a circuit that produces clocked randomly changing control voltages. These can also be locked into loops that repeat every 8, 16 or 32 steps.

This is an open hardware project – all the project files (Eagle CAD projects, Gerbers PCB files, a Mouser BOM and Illustrator/PDF front panel designs) are available on this page, covered by a Creative Commons Attribution Share-a-like license, which allows for commercial use.

This is a relatively advanced DIY project, and I’m not able to provide support. I am not selling PCBs, kits or finished modules, but hopefully all the information you’d need to get your own is here: Getting the parts to build a random sequencer. Update: You may be able to buy full kits from thonk.co.uk

The obligatory video demo:

A few audio demos:

As a sequencer:

One random sequencer controlling a Dixie oscillator clocking a second random sequencer acting as a wavetable oscillator (phew!):

Documentation and build documents 

(All CC licensed)

The latest version is v2.1, which fixes the capacitor polarity issue in v2. V2 schematics and documents are below.

random sequencer documentation v2.1

– This PDF file contains the schematic, block diagram, how the circuit works and how to build the PCB.

random sequencer v2.1 schematic 

– Large png image of the rather scruffy schematic. It’s all there. If you want to examine the schematic in detail, the Eagle version might be easier to navigate.

random_seq_2.1_gerber files
– This is a zip file of the files required to make a random sequencer PCB, optimised for iTead studio’s PCB prototyping service. Step-by-step instructions are here.
random_seq_2.1_eagle files 
– These are the Eagle project files if you want to work on the schematic or PCB layout yourself. They’re compatible with the non-commercial version of Eagle 6.1.

Random Sequencer Panels – pdf + illustrator

Random sequencer panels – pdf only

– These contain the files used to create two different styles of panel for the sequencer.

Background and research documents 

Random Sequencer Reading List

– A collection of web-sourced background material about the history of random voltage sources and shift register sequencers, including: pages from Allen Strange and Hal Chamberlin’s books, interview transcript with Don Buchla, documentation for modules from Grant Richter and Dieter Doepfer and an essay on process music by Steve Reich.

Random Sequencer Datasheet Collection

– PDF datasheets of many of the ICs and other components used



Old versions – these contain errors: 

random sequencer documentation_v2

– ImportantPlease read this addendum before building using the v2 instructions above.

Random Sequencer v2 Part Placement image

Random Sequencer v2 Schematic

Random Sequencer v2 Gerbers

Random Sequencer v2 Eagle


Licence: This is an open source hardware project. You can use this design however you like, including any modification or commercial production, so long as you credit Tom Whitwell and share your own changes. Random Sequencer by Tom Whitwell is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
Creative Commons License


  1. Michael Hank says:

    Hey Tom,

    First of all thanks a lot for your Turing sequencer project. I’ve built two for myself and love them to bits!

    Now I’m considering building a run of 10 or 20 to sell at a profit.

    I understand this is licensed under creative commons.
    Nevertheless, I’d find it just fair to have you participate with the proceeds if this pans out.
    Do you have a specific amount per module in mind?
    I’m also willing to donate to NGOs or muffwiggler if you prefer this.

    Are there any other things to take into account besides crediting you as the creator of the project?

    Thanks again, greetings from Berlin


    • Tom Whitwell says:

      Hi, you’re completely within your rights to sell these at a profit, so long as you make it clear that you are the manufacturer, and not me.

  2. vogelmach says:

    Thanks for this.Great Module !
    Keep up the good work.


  3. John says:

    This could get addicting. The random loops sound very interesting. For someone writing songs this technology could be a starting point for melodies. A good composer could take some of these random patterns, work with them a create a song.

  4. Matt says:

    This looks amazing! Does it work on +/-15V as well?

  5. SirSickSik says:

    Hey there, just found out about the existence of your module as I’m taking over a pre-build module of someone.

    I haven’t yet tried it myself, but seeing from the video’s I get the feeling your setup could be well used for an arpeggiator I came up with last month as a vst. Instead of outputting random voltages or very basic arp, non-changing patterns, it creates ever changing patterns based on several steady input-values (which could be randomized very well using the turing machine’s already existing architecture).

    I’ve combined several (already existing) simple ideas and combined them into an arpeggiator which can go from all basic arp-patterns up to very complex, but ‘followable’, patterns, using just a couple of knobs.. The only part that took 8 extra knobs, could be interchanged with the turing machine’s random voltage generation, which could make it one of the best arpeggiators around, using only about 4-8 knobs, BUT having the possibility of creating ANY melody there is while just using an arp…

    This probably all sounds very arrogant, but I rather think about the fact that I just want everybody to have this possibility for a low price. So I would like to propose a collaboration to put this vst-module into modular existence :)
    For demo’s of the arpeggiator (+chord progression vst and my own build vsti synthesizers and effects):


    (for communication just send a message to my e-mail if you can see it or, otherwise, follow the link and send me a message through soundcloud)

    • Tom Whitwell says:

      Hi, sounds like a fun project for someone wanting to do an Arduino/microprocessor based module – that’s not something I’m really interested in at the moment, I’m afraid.
      Best wishes, Tom

  6. Damo says:


    I’ve just completed my first ever pieco of modular kit, turing machine (baptism of fire I know) and i was wondering what power supply best would suit it for there in the uk?
    I’m also wondering if there are any midi – cv adaptors on the market that would allow me to send my midi clock from ableton live via my interface to the turing machine? I fully intend to integrate this into my live techno setup once complete with the expansion in order to give an element of total randomness to each and every appearance, will prob be trying it through a sherman filterbank also.

    Apologies for the noob questions,



  7. Tom Whitwell says:

    @dano There are lots of solutions out there – many people swear by Expert Sleepers as a good way to integrate software with modular without having to go via Midi at all: http://www.expert-sleepers.co.uk/

  8. Toby says:

    Hi Tom

    Sorry if the answer to this is the same as above, although having looked I am not entirely sure it is? A luddite question….

    I have to confess to being a newbie to modular synths.

    I have done DIY midi projects before etc – and actually without sounding lame I really just would like to build the turing machine as a stand alone sequencer that I can have in a tiny case to sequence my outboard hardware 303 & other monosynths, as opposed to going into a full modular setup.

    so presumably I need to covert the output of the Turing machines / CV ? Gate or the relevant components to a midi out signal. I have been reading the forums but they seem much deeper that this. I was wondering if you could provide guidance. Is what I am saying possible and sensible?

    Ideally it would take a midi clock in so the tempo could be slave to a DAW and it clock off that, or via USB. And then it would need a midi out generator which I guess would have to patch in the relevant outputs of the turing machine.

    I am not going to lie, I don’t entirely understand all the outs on the Turing machine despite fairly lengthy reading so I was thinking you might be able to provide me with a definitive answer.

    Really price is an issue, I don’t want to blow loads, so something effective and simple would be good – I have looked on modulargrid and been going thourgh that but the welath of choice is overwhelming for someone who knows so little.
    any help hugely appreciated.

    Many thanks


    • Tom Whitwell says:

      Turing -> Midi?

      You’d need a power supply/case for the Turing, and a clock of some kind – a square-wave LFO, and a CV-to-MIDI converter.

      That’s a LOT of infrastructure!

  9. Chris says:

    Hi Tom!

    I got a turing sequencer on ebay built by a guy in france, worked like a charm and love it, but now it does not power up, it’s dead! are there any online references for where I could check what’s wrong with it? I have built some other modules on my own and have service techs at hand for stuff that’s out of my league. big thanks!


  10. randal says:

    Hey love this website! I’m an engineering student/musician. I love how hardware is becoming more opensource like software. Ever hear of upverter? It’s like the github for electronics. Its sorta new (2010)

  11. Kyle says:

    Turing Machine is a work of genius!
    That with a quantizer (Penrose) is so addictive!!

  12. Hi everyone, i really enjoyed turing machine with both expander, everything went well but when i added bytes expander by circuit shaman i have now weird sequences repeating from high to low notes very often with the lock knob at 12 oclock. I’m posting here because he doesn’t really know why… Maybe someone had the same issue, i would really appreciate some help. I made a video if it can help. Thanks ! —> https://www.youtube.com/watch?v=1SErd4bfeek

  13. Hi Tom, i finnaly removed bytes expander because of the issue i just posted before, but i still have the same issue without bytes expander… Do you have an idea why ? It was working fine before i tried to add bytes… Here’s a quick video, thanks https://dl.dropboxusercontent.com/u/369715/Modular/still-same-problem.mp4

    • Tom Whitwell says:

      Hi, sorry to hear that. I don’t know how Bytes works, and I’m not sure exactly what problem you’re seeing. You seem to have random changes, I can’t quite tell if you’re getting normal locking/looping. Problems with locking are most commonly caused by the noise transistor – LOTS of discussion of that in the Muffs thread.

  14. Hi Tom, i build a new turing machine (only the main turing, without expanders and backpack). It has the same weird behavior as my other one. It was a new kit, from thonk and i really made sure everything was perfectly soldered and spending extra time to do it right. So now i have 2 turing machine that have the same issue. I thought the first one was because of the bytes expander installation but now that i built a new one with a new kit i really don’t understand what is going on… Is it possible to talk with you by email or something ? Thanks

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