OLD Turing Machine Random Looping Sequencer Documentation



The Turing Machine has been updated to a new version which is easier to build and more powerful than the original design.

Kits available from Thonk

Design files are on Github




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

    • Tom Whitwell says:

      Sorry, I can’t help with Bytes – you’d have to contact Circuit Shaman and ask him.

  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

  15. Arnaud says:

    Hi Tom,

    I was about to make an order for a turing machine kit on thonk, but they just went out of it ;( … Any chance you’ll be sending a batch soon ?

    Thanks for the great work,


  16. Dieter says:

    Hi, I’m brandnew in that module-world so forgive me my
    question: Is there sort of a “manual” for that turing -machine?

  17. Khew says:

    Hi Tom,

    I’m wondering if I could use a 500K or 1M pot for the “Scale” instead of the 50K? Would there be any major issues doing that?


  18. Norman says:

    Hi Tom,

    since I’m a novice in building electronic devices I’m wondering whether it’s okay to replace the MLCCs in the circuit with e.g. mylar caps. Are there any precautions (concerning frequency response etc.) to take into consideration?

    Greets from Germany,

  19. Simon says:

    Hi Tom

    Having seen the video from superbooth on sonicstate, I am no planning on building one of these fine modules. However before I place an order on pcbs for the mki, I would like to hear if you are releasing the gerber files, BOM and everything for the mkii?


  20. Ronald Vonk says:

    Hi Tom,

    I have build a Turing machine MKII and it works fine except one thing. The CV out is not random, but it builds up to max in a few steps. Clearing the buffer and filling it again does reset this behaviour, but then it starts from low to high again. I already asked this in MuffWiggler and other forums, but no response so far. Any idea were to look? I checked everything, tried to understand the schematics, but I can’t find a clue.

    Cheers, Ronald.

  21. Dave Bunch says:

    Halfway through assembling my Turing Machine Mk II & I can’t find ‘1N4148 diode’. I’ve been very careful with the many parts that came with the DIY kit – 1st thing I did was put them into 2 bowls as the instructions suggested. I guess I’ll have to get the missing diode at MicroCenter.

  22. David says:

    Hello,, im building turing machine mk1 with expanders,, so i have a problem on the random seq,, just turn on 2 lights on the display and when i connect the backpack expander it won’t turn on,,, any help , any tip ? i been searching for the problem but still don’t get it….

  23. Ben says:


    I’ve received My kits modules and it’s Nice as usual.
    But with the Turing machine i have a problem that i can’t solve.
    I’ve done everything as precautionly as it Can be, and follow all the steps. I verified twice, but the Turing machine don’t lock the sequence when i turn the potentiometer clockwise. I have a video imaging this. Can you help me, what Can i do… I see that there are some discutions about that on forums… Your job is awesome, thanks, cheers from France 😉


  24. Roy says:

    Say hypothetically I hooked a power lead to the pulses module by mistake. And say that broke the top two and bottom dual pulse outputs. I looked at the board and don’t see anything obvious. Any guesses which parts I might need to replace?

    • Tom Whitwell says:

      Was it hooked to the main module at the time? If not, the only active component is the chip. If so, you might need to replace the AND chips on the back PCB of the main module.

  25. Doug says:

    I see a previous question asked if it’s ok to use a 500K or 1M pot for scale control. I don’t suppose you see any possible issues using 100K for scale control instead of 50K?


  26. Mike says:


    Would it be possible to make a quantizer expander for the turing Machine that picks up values from the loop and uses them to allow steps in the scale? This would allow for evolving scales as another way of steering the melodic stream of notes.

  27. I’m desperate for a Turing Machine Kit! Only just getting into modular and Thonk have been out for weeks. Such an awesome bit of kit. Well done! 👌🏻