Eurorack module testing tool (DIY)
  • I had to face two problems during the development of the modules:

    • How to power and test them during development? A bench-top supply and signal generators? Too big and overkill. My rack loaded with precious stuff? No way I would let a scope probe shorting two pins impact them!
    • What kind of setup to use for factory testing? A Doepfer mini case loaded with LFO/signal generators? Too expensive, and hard to operate.

    I decided to find a DIY solution, and designed the following box.

    It serves the following purposes:

    • +/-12V and +5V power supply with euro connector.
    • 4 signal generation channels dedicated to clocks (tempo, resolution, pulse width); gates (period, pulse duration); CV (several waveforms, sequences stepping through 1V/Oct octaves or scales); and audio (fixed note/frequency tone generator with various waveshapes).
    • 2 signal acquisition channels, one is audio with frequency and note interval measurement (for V/Oct calibration) and the other is digital for clock testing/calibration (frequency/tempo measurement; and pulse width).

    Maybe this might be useful to those of you building DIY modules and wanting a quick test/debugging setup less cumbersome than signal generators or your modular setup?

    It won’t go farther than Board+programmed MCU+Mouser BOM with very minimal assistance provided (no building instructions etc). This might be useful to hardcore DIYers only anyway!

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  • Very interesting tool Olivier, leave it to you to innovate this way.

  • a diy diy tool – very self-referential. ;)

  • oh nice.

  • Very cool I’ve been wanting something like this for ages!

  • yep where do I sign up ….

  • I think this will be helpful for me (and probably many others) make friends for my surely inevitable MI modules in my now inevitable eurorack case

  • Oh yes! Will free up a bunch of eurorack modules currently being pressed into service as signal generators, and I’ve been looking for a better frequency measurement solution than my multimeter for a while. Want!!!!!

    PS What sort of MCU does it use?

  • Good old ATmega… It’s a very simple Shruthi-like through-hole board.

  • Its the 3nd most usefull thing right after sufficient gravity/air/light and a Scope when developing something Eurorack/DIY

  • Interested…

  • Hmm, this will go into the cart when available.

  • Will there be a FrankDanielsPlexiCase™?

  • Available on request.

  • I think I’ll get one of these when it’s available, I used to be powering my breadboard modules using a one meter long ribbon cable plugged to my euro case, and was always worried I could fry my real modules, then I started to use a separate Euro PSU, but it’s cumbersome… This will come handy!

  • Could this be modded to other modular synth formats, i.e. +/- 15V and MOTM?

  • +/- 15V -> change the regulators. MOTM: this is the format of the connector, right? Or any other change?

  • yeah i’m up for this one too¬¬!

    really great idea.

  • @pichenettes: yeah, power connector format… if there is a place on the pcb to add an extension connector with +/-15V and all I/O so one can build a break out box with MOTM and style power connectors and a bunch of 1/4” 112AXes.

  • @kvitekp: There’s always this :)

  • Yeah, however if I only use 1/4” investing in a bunch of 3.5mm conversion cables just for testing purposes may be an overkill… besides, it could lead to a Euro rack project start which is not currently my plan ;)

  • That’s awesome. Where do I sign ?

  • Any updates on this? Planning to start euro DIY projects in a few weeks. This would be a perfect first project :)

  • I don’t have much time at the moment to document this. The only thing I can do is order boards, flash chips and post a BOM...

  • That’d be enough for me. Especially considering that I’m sure there are other folks who will be building as well and we can act as a self help group a la fcd72 programmer

  • Plus, I am guessing it will be at least reasonably intuitive given MI tradition. More likely will feel like second or perhaps first or <1st nature…

  • +1 to Joshuagoran’s comments…

  • I think this one is a tool for the more sophisticated DIYer, so there might be next to no problems ahead. Someone eho isnt able to source the Parts according to a BOM or just stuff the PCB couldnt hardly make any use of this device anyways….

  • +1 on above. Boards, schematics, & BOMs should be more than enough.

  • yep. that’s all i was expecting anyway.

  • PCB ordered. I will publish the BOM soon. It would be great if you team up for buying the fancy parts (switches, Erthenvar jacks…) and dispatching them within EU. This is not something I have the time to do.

  • Code posted on github . I’ll create a page on the website to mention this and that’ll be all for today. See you in 2 weeks when the PCBs will be delivered!

  • If anyone is interested in a Case…. i guess Olivier won’t dispatch these, too.

  • want one !

  • I want one too!

  • +1 for case too fcd.

  • +1 on both a PCB and a case.

  • Now who organizes the rare parts???

  • Case and PCB for me!

  • Should there be an announcement over at Muffs?

  • Please not…... else Olivier would be rushed to make 1000s of these ;-)

  • +1 for a case. I just ordered the jacks. I’ll give some away since they aren’t needed.

    Anyone in Europe want 50 jacks and nuts to pass out for this? I rather send them to one person….trusted by post count. Damn I forgot the washers.

  • How about Frank? Order a case, go nuts ;)

  • Please do not announce this project elsewhere for the moment. Let’s do a first (small) run, and see how it goes. I suspect this thing might end up costing me more time/money than it will bring, so the last thing I want is seeing this loss getting bigger as more people get in. This project is very similar in parts/design to other MI products so I’m sure you won’t have any problem building it. Random guy on muff? Not sure.

  • “Random guy on muff” – nice outlining ;-)

  • i’m in for one PCB too with an fcd case :-)
    Will there be programmed chips with the PCB? I don’t have a programmer (yet)...
    Did I just say programmer??
    What are the rare parts here, apart from the erthenvars?
    I think the lm4040 vref was not so easy to find… as well as those caps (I have a few of them left, in white).
    The erthenvars jacks can be found at for europe, they go for 14 euro a bag of 50 jacks with nuts.
    I have about 80 of them left that I can ship, and I might place a new order to Thonk quite soon for their new Turing Machine expanders so wouldn’t mind getting more jacks if needed and shipping them.

  • okay, I suspected this might be the case, so I am glad I asked! just wanted to see if more = better :)

    I do think once any kinks are worked out, there may be lots of interest, though! if that means expensive PCBs or whatever to make it worthwhile, I bet folks would still sign up.

  • Maybe you can talk me into providing the Rare parts (Jacks, LM4040) to be bundled with a case?

  • Yes, that’s a very good idea. :-)

  • I have a bag of 100 of these jacks. willing to spread the love for the price of a stamp :)

  • Yay!!!! +1 for case!!!!!!

    PS maybe thinking aloud – would a 7805-replacement switcher be OK to use in this device, such as this one ?

  • I would love to have one. :)

  • I actually have one board left from the initial run – it’s working but there are two or three parts values which have changed (10nF becomes 1nF ; 100k is swapped with 150k for one or two resistors – cross-check with the blueprint!). If you are interested, write “Preum’s”, check that nobody else has posted before you, and buy an Ambika voicecard of your choice + drop me a message about your need for the board. I don’t have flashed chips at the moment, so I’d rather see this one go to someone who will know how to flash the chip!

  • Preum’s

  • and this one goes to stimresp!

  • Jacks arrived very quickly from Erthenvar. :dance:

  • There were a few confusions about the order that caused a delay in the processing of the order (I had ordered… white soldermask with white silkscreen! and the revised Gerber layer with fixed component values did not line up with the one from the previous order because I now work with two Eagle .CAM setups) – but finally everything is sorted. Scheduled for May 18.

  • @pichenettes: awesome.
    @fcd72: + 1 case and +1 in trying to talk you into providing rare parts ;)

  • @pichenettes: Just one thing on the project page on the site-it refers to a “+/- 12V AC” supply…

  • Yeah, another wall-wart to buy :(

  • 12v ac ac. the -+ part: does that mean I need to look for an adapter that swings 24pp? or will the 12v acac I have already be ok?


  • I see, this is not clear. The one you have linked to is OK. Basically the same thing as for Ambika, but with 12V output instead of 9V.

  • ah. perfect. thanks.

  • +1 for PCB only (if I’m not too late …)

  • count me in for PCB only variant

  • nice.
    am I right in thinking this could power a single Euro percussion module/mega percussive synthesiser or something and also act as a MIDI-CV converter so that I could trigger said module from octatrack?
    Would this be limited to just one throughput or could you run more than one MIDI-trigger pathway through in like manner?
    or am I getting the wrong end of the stick? I know this isn’t the primary purpose :)
    Thanks – jk

  • @bendyjohn
    It only converts MIDI to ONE trigger, thats enough for testing purposes but doesnt quite match your specs. You obviously want a MIDI>Trigger converter like this or that

  • The design of the mysterious C would shurely fit nice into the death star !!!

  • Apparently it is part of the DeathStar™ you can spot it in Episode 4 and 6 in the Death Star Laser Firing sequences.

  • Now reminding hits me…Bye, bye Alderaan !

  • Please update sir. :-)

    There was a KS to build a death star. I think it failed to reach its goal.

  • Delivered on next tuesday

  • Je vous remercie!

  • ...And a PCB? I would buy it.

  • sorry for delayed reaction – thanks fcd72 for answer there, couldn’t follow yr first link [& kind of expected the second ;) ]
    but that’s what I needed to know – just one MIDI to trigger, probably I’d better leave this one to the big boys with rigs to test! Will figure out a budget solution. Big C happening with royalties of first hit I make without it! ie – get real john :)

  • i’m in :)

  • :-D yawn….now I can sleep well.

  • Cases also available… if you can make use of this you probably know where to ask….

  • @fcd you have mail ;)

  • purchased-yay! bedtime now….

  • Fcd72 how much for a case?

  • I will have to calculate, about twice the Shruthi i guess since its about twice the size.

  • huh? does the board fit into 3U euro rack?

  • I don’t think it does, and let me tell you, you are having very evil thoughts.

  • i’m totally innocent :)
    i was thinking of putting some tools in one big metal case but that would make it kinda stationary. i guess a mobile testing tool would be more useful since i only build them at home and it’s a quicker job to take the tool with me when something’s wrong

  • It doesnt fir as long as you want it parralel to the Panel. Sadly. I tried.

  • yeah portable box for sure. racks are bad mkay.

  • My envelope arrived in my non-rioting part of Stockholm. That was seriously quick! And there was much rejoicing.

  • what? you take notice of what happens off-synth? or off bench
    i was too late for pcb+ ATMEGA tonight so i’ll have to learn flashing again :D

  • Bizarro, ain’t it? I figured I’d also do the flash and the pan for this one.

  • ETA on more PCBs with programmed chips? Waited until payday and poof! Chips sold out.

  • I have flashed a few chips and update the stock status. But I don’t understand… You’re buying this because you do a lot of DIY, why don’t you spend a bit (at most 30€) to get a programmer?

  • Because I keep convincing myself that I don’t need one, that the Shruthi, then the MidiALF, and now this is the last Atmel project I’ll have for awhile. Of course, I think you know my habits and those of similar folks better than I know myself :)

  • Programmer will pay itself off very fast-if you’re like me, once you’ve used it once you’ll feel astonished how easy it is to use, and ashamed you ever bought pre-programmed chips-get a cheapo betemcu one from eBay, I’ve done 2 Ambikas worth of chips with one!

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