Need Some Clarification From Modular Veterans (Time-Sensitive)

  • EDIT: See bottom for newest question. I've kept the conversation for those interested in my thought process from noob to semi-noob.

    Hey there guys, I've been working on my newest project, building a DIY small-form modular, and I'm not sure of some of the technical issues.

    1. I'll be building an Octomod to control the modular fairly cheaply, I priced all the components and the price came out to about $90 for that.

    2. I was thinking of getting one of the Doepfer A-100 mini cases ( and building a VCO and VCF, to start. Was thinking about these:
    Particularly the VCO and the miniMoog VCF.

    I'm fairly confident with electronics, and am pretty sure I can get through tuning the VCO with the gear I have at my college campus, but not sure about certain things relating directly to modulars.

    First, his VCO claims to be +/- 15 V (actually 14.2 V), is that alright with the case that claims to be +/- 12 V? Would it not correctly power my module?

    Secondly, in terms of the connection ribbons, the case looks like it uses something like an 8 pin cable, whereas his DIY modules only use 4. Is there some conversion factor or difference between older and newer cables?

    Last, don't I also need a VCA? I just realized I might have to build one of those as well.

    Thanks in advance for any help, it's just boggling my mind right now and I don't want to blow anything up haha.

  • Hey MCDELAT,

    In terms of what you need it depends what you want it to do, a VCO and VCF are just going to produce straight tones with some filtering on it, without an envelope it's going to be fairly limited.

    What do you want to use it for sound wise? You probably at least want a VCA and you'll need a midi/cv converter of some sort as well to control it.

    I'm currently building a DIY modular as well, since it's my first one I started with a thing called the ASM-2 from elby designs, it has a moog ladder filter on it.
    A good example here
    the early 90's looking product page is here

    It's a big PCB with a whole lot of discreet modules on it that you can wire up to make a whole modular synth. I'm calling mine deathklok and I'm building it as a 6 rackspace monolithic panel for now so that later I can use it as part of a euro rack rig. I've just started researching case designs.

    Research, designs and build log here

    If you want something simpler to start with you could consider the music from outer space sound lab, it's modular but it's self contained so if you're starting from scratch it's fun right away. They also have an insane amount of DIY resources.

    badass example of the soundlab here

    I kinda figured since I didn't already have a modular that if I was going to do DIY I should build something fun out of the gate, once I have my system up and going I'll probably start making more individual modules. I also have a vague plan to build a spare arduinome kit I have into the synth rig and run stuff lik polygome as part of the modular rig on an EE PC.

    Sorry I couldn't answer the technical questions, I have to google for that stuff myself =)

  • Dur, I just realized what the octomod is, I guess you'll already have a CV interface then......

  • You should have no issues with eurorack power with the octomod. I've been talking with Greg since day one (I'd like to think it was my advice that made him actually go ahead and build these things ;-) I have an octomod (unassembled) and I'm on Eurorack power, it's just designed to work with both, it spits out +/- 5v for the CV.

    It's well worth emailing Greg, octo build isn't the best detailed online, but he's super helpful.

    re ribbon cables, as long as you have the right cables going to the right pins you don't need all 16 of them, check here for more info


    VCA, yes indeed you will. As it is with your 3 module setup, you'll have a vco that makes a constant tone based on a cv from the octomod, that is filtered controlled by other parts of the octomod. VCA's are thankfully pretty cheap to make or buy, and come in very small sizes.

    last tip, head over and register at you'll thank me later. ;-)

  • Thanks guys for your advice, you've resolved most of my questions, but there's still a couple of things I need to figure out.


    I'm not quite into the soundlab mini-synth myself. I'm looking to the future where I have a full modular, so I want to start building now.

    I understand that my 'musical palate' will be a little limited with just a VCO, VCF, and VCA, but that's all good. I'll just do stuff in Ableton to process it if needed until I find more funds to increase the size.

    Octomod build seems relatively easy, so even without documentation it makes sense. Throw his code onto the teensy, get all the components on the board, and you're pretty much there.

    My main concern here, which wasn't addressed was:
    Since all the yusynth (link above) modules are +/- 15V won't the Doepfer case that only carries +/- 12V fail to power on my modules completely?

    Any other recommendations on DIY modules that fall into that voltage?

    EDIT: Seems like every DIY site is using +/- 15V. Am I going about this backwords? Should I be looking for a different case that supports this voltage?

  • if you looking for a VCO module i have an SN voice kit with pcb plus voice chip that i'd like ot sell on.


  • "most" diy stuff handles +/- 15 but works great on 12v, my guess is it's easier to handle more than boost less.

  • @JP
    So any modules I build should still work fine on 12V? Theoretically?

    What price would you think about for the SN voice? He doesn't have it listed on the page anymore as far as I can tell.

  • cost me 140 euro or so altogether (chip + pcb + parts kit)...

    100 euro plus shipping? will be shipped from ireland.

  • re the SN Voice, it has almost everything you'd need, but it also needs tweaks to work with 12v.

    EM seems to be down at the moment, but there's a whole giant thread on there about it, including what's needed to do the conversion and some panel designs.

    Google cache:

  • IIRC, there are 1 or 2 part subsitutions (nothing major just caps and resistors) that may be required to use the SN on a 12v system. some seemed to think it would work fine as is.

    when electro music is back up, do a search for sn voice 15 volt/12 volt and you'll see a thread on the subject with details.

  • It's also worth looking at something like Doepfers new all in one DIY synth panel.

  • Public question:

    I'm noob at the modular format, sorry.

    It seems I'll end up going with the SN Voice, but I have one last question that will help me out a ton. I can't seem to find a guide on how to actually attach the ribbon cables from a module to the case.

    I just want to more or less, how this is done, because the SN voice appears to have 3 sets of 12 PIN cable locations. Since the A-100 mini case only has the two cable formats (10 and 16, seen above) what do I do?

    What about the cable set found here:

  • @custardweasel
    Hey, I'm building an ASM-2 as well. I'd be interested to see how yours turns out as that there don't seem to be many out there completed... mine's been sitting for a while. The hard part for me is deciding how exactly I want this thing to patch out and how small I can make the front panel without it being cramped.

    I was thinking of using 1/8 inch jacks instead of the usual 1/4 inch. Any thoughts from anyone?

    ...aha! reading up on the deathklok as we speak ;-)

  • @talks.

    Per 1/8" vs 1/4":
    That mostly depends on if you think you'll be adding others modules to the rack. If you don't plan on adding anything else to your rack besides the stuff from the ASM-2, then go with what your hearts contends. In terms of noise I don't think either cable is more susceptible to it.

    If you think you might want to add other modules in the future though, go with the same size, that way you don't have to do a bunch of 1/4 to 1/8 conversions.

  • Personally I can imagine patching with 1/4" but MCDETAT is right, it's about the format you choose. I know nothing about the ASM so don't know if it's Euro compat. If it is, it would be a no brainer to go 1/8" and tap into Euro format.

    Quick google brought up this

  • Can anyone answer my question about how you make the ribbon cables and wire the module to the case? (See above)

    I've been staring at the problem for a while and don't think it'll just come to me.

  • hey MC, not sure if i follow you correctly, but those headers and the other ednd of those ribbon cables will go straight to the jacks and pots. is that what you mean?


    You should head over here and read through and if no one has asked, ask.

    j1, j2, j3 are the power +15 ground -15, you'll probably just need to make your own cable to header so that it can plug straight into the euro busboard.


  • @JP

    Okay cool, I think I figured it out once oootini pointed out that the posts are for the pots and 1/4" jacks. So correct me here if I'm wrong:
    I'd buy a cable that has the female header end already in place, with the other end just cable, then I can separate them and either solder directly to board or put my own headers on.

    Which reminds me: is it more customary to solder the jacks and pins directly to pin or to to put down headers and put the wires directly into that, so they can theoretically be removed?

    Thanks for all your guys help, I think this project makes a lot more sense now. Steep learning curve it is.

    I'm planning the to heavily document the process and perhaps even turning it into an instructable? Mostly because I want the leap for some to seem less scary, because currently it's not truly documented in any one place.

  • the ribbon cables you need with the headers on one end and bare at the other end are included in the kit (i think). will check when i package it later. if not, the connectors definitely are, which means all you need to do is buy a roll of suitable ribbon cable.

    so basically you solder up the board with components, and then snap the ribbon cables to the board, no need to solder them down. this allows you to easily remove the pcb later for mods, etc. the other end of the ribbon cables are soldered directly to the various control pots, jacks etc.

    it'll all be fairly obvious once you have the kit in your hands though.

  • O ok cool. That makes a million times more sense. I probably will figure it out, but just want to make sure, because I don't want to blow any of the DIP packages.

  • you'll put a socket down for all the chips, which will allow you to test the circuit with power before putting in the chips.

    like this:

  • HEY there guys, I have a really important question and I was wondering if you can help me on it.

    As some of you may know, I am leaving the country very soon (on wednesday in fact) so I'm trying to finish up my modular build, but in case it doesn't happen the way I plan I absolutely need this question answered:

    I'm building an SN Voice. I'm about 60% done wiring things up and then I'm done. I might be able to finish it, but between packing and preparing everything else I might not. So my question is can I go ahead and test it without the front panel all wired up and properly tying itself to the circuit.

    Aren't wires such as this "conditional" parts of the circuit? If so, I plan on wiring up just the last few jacks of importance that meet it's "functional" state. I.E. I can use my CV controller and get all the different sound waves out. Wether I can modulate them is a different story. I just want to test if it is working.

    Is that doable? Suggested?

  • you mean you have all the pots hooked up but no grounding for them via a faceplate?

    AFAIK you will need to have the pots wired up though. if you do, you could totally give her a test run! you might get a wee bit of noise from the ungrounded pots but it'll still totally work...

    go for it!

    pics/samples or it didn't happen :)

    and good luck with the south american adventure.

  • No. I have 60% of all the components hooked up. A row of jacks, most of the pots, and 1 switch. Wondering if I can just hookup the input (outputs are done) jacks to see if it even makes sound.

  • maybe just split the difference in value for the remaining pot values with temporary resistors? ie for a 100k linear pot, just plop in a 50k resisistor.

    not sure about equivalent log pot values though...

  • ok yeah. I'll take a look. Really hoping I have time to get some sound out of it today, but the odds are shaping against me because I still haven't boxed up anything in my house for storage.