# Working Clock Multiplier/Divider/Phase Shifter with tolerance for uneven clocks

Possibly something like that… Im just a desktop user and use Linux on my ancient laptop in my workshop but Windows on the home pcs. I dont really enjoy programming or pc based music creation at all, that s why i first got in to making analog synths with real knobs - but i recognise that there is a lot of power in the digital if someone else writes the program and i build the hardware…

Bit of a correction here:

It seems that the clock outputs aren’t giving enough amperage to some modules that seem to need it.

I’ve built the Unauthorised Service Snare stripboard, and I’ve found that with this clock multiplier, it doesn’t get enough to do its job. Now I know I haven’t really gone over the snare that much yet, and perhaps there are things that can be tuned (though I feel like it might be the regulator itself not getting enough amps to get started), but looking at what I’ve done, I can see that 100k resistors on a 5V output (just something I did without thinking too much more beyond protecting the outputs) only delivers 0.05mA which feels very tiny.

Most other projects that use Arduino Nano appear to use 1k resistors which allows for 5mA output, for some reason I couldn’t find any here (travesty!) so I’ve chucked 1.8k resistors instead of the 100k resistors on the outputs and everything appears dandy again and I have my snare firing again.

I’ll update the stripboard layout unless anyone has any pointers or suggestions (other than using opamps on the output, I’m trying to keep part count suuuper low).

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Yeah, the “standard” output resistor for modules is 1k, I think. A single Arduino pin can put out up to 40mA (200mA on all pins together), so you should be safe with a 1k resistor when you short the output to GND (and also against -12V, I guess? ~18mA?).

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Right, output impedance of 1k is common, and input impedance of 100k. Not an absolute rule but typical. 100k output resistors are way too large to drive a lot of modules. If you worry about how much current the Arduino can source you can buffer the outputs with op amps or transistors.

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This is great to know - these kinds of little things are hard to find sometimes when getting into this stuff. It’d be nice to have this kind of info somewhere alongside the eurorack definitions or Kosmo definitions etc so you know what power things run on, the signal strength of CV and audio, and also just this kind of general interfacing info.

40mA per pin should be enough for most things per pin of the Arduino, some modules are super intense to build, I’d like to keep this one pretty basic in terms of hardware because the software was such a brain-burner.

Thanks!

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@jessecakeindustries

Im not sure if you have seen this thread yet, contains a spec for Kosmo modules

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Including, indeed, typical input and output impedances!

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ha! Well there you go - taking something from the Linux world: RTFM - lesson learned

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Hmmm now that I’m looking at this though, it specifies impedance, but sometimes voltages might be a little different etc, so would it not be more important to list currents for outputs?

I noticed some people make CV outputs 8V, some from Arduino based stuff are 5V, but a 1k resistor will be different current output depending on voltage. Not by massive amounts, but probably an important distinction to make?

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Well, it does list voltages, and that plus impedance will give you current. But it’s called control voltage for a reason, not control current; it’s the voltage that matters. And if the output impedance of one module is too large, or the input impedance of another module is too small, then the open circuit output voltage becomes a smaller, maybe too small, voltage when connected to the other module. Think voltage divider: 5 V at the top of a 1k resistor becomes 4.95 V when connected to a 100k to ground, but if you use a 100k output resistor instead, that 5 V becomes 2.5 V.

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That makes sense. I guess I always have in the back of my mind that some things have buffered inputs using transistors from time to time that need current, less so voltage so that’s where my mind went, but if using an op-amp then it’s more about that voltage following.

I do love how varied and weird modular synthesis seems to be. Definitely a world I’ve enjoyed throwing away my idea of what it was as I learn more. I guess it’s like most things, the more you learn, the more you realise you don’t know - there was real bliss in being 20 years old and thinking you knew everything about the world haha

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Ha! I literally just came on here to bring up this exact point based on my use of the modile last night, including suggesting the 1k output R instead of the 100k!
I realised what was wrong when i plugged in my synth scope and saw a 2.5v trigger pilse when plugged anf a 5v when free…
Normally i think i would have twigged sooner, if it were an analog module but im not arduino experienced…

Id agree that standard would be 100k in, 1k out.

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I agree that some kind of intro into electronics for modular synth would be nice! Like a collaborative online book where these basic things are explained… like: I know how to use a soldering iron, I can use the ohm law pyramid, but what else do I need to know to make my own modules?
So, the specs combined with some best practices, common circuit parts (buffers, led drivers, Arduino protection, …) our basic debugging infos from the forum… maybe in form of a Zine?!? XD

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I believe you just described Make: analog synthesizers by Ray Wilson

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I do love a zine, less formal and allows for each focal point to be a separate edition. I’d totally be in for helping on a photocopy vibe cool zine. Would make things nice and accessible

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Wow, so O’Reilly no longer sell their books?!

When did this happen? I just went to go buy the ebook and I can’t. Seems they’ve moved to some weird subscription setup.

When will places stop this whole paid rental membership madness?

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I’m not sure! I’m on the other side of the ocean, for me I can still order it from the local bookstore.

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I haven’t actually read that. I took a look at the Amazon reviews and found one that said

Just check out ‘Look Mum No Computer’ on YouTube instead. He actually shows you how to build a synth bit by bit.

Heh. Love Sam’s videos but I’m not sure he’s always the best builder to emulate.

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This subscribed DRM book nonsense drives me mad, even ebooks you think you are buying, you often only have the licence for as long as the provider wishes to maintain and can be revoked.

After losing access to a fair few reference books I had paid for, with a large reputable supplier, while studying. I have now reverted to buying hard copies of any such material. It is just too expensive and inconvenient to lose without notice. This is not very environmentally friendly, and could easily be avoided if it was not for the greed of corporations.

On a positive note, the author of the linked book, also has a website with lots of information and schematics, although navigation takes some patience.

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Yeah I know what you mean. I’ve always done my best to avoid DRM books, which is why I loved O’Reilly so much as their books were famously DRM free and they were always about making sure you had access to download your books with updates forever which is why I almost feel grief now I’ve gone to check in on my books from there.

I struggle with physical books sometimes as I like to read late at night, and my Kobo e-reader is light and easy to use for that, though I do appreciate physical media.

Even things I build from plans I print and keep in a “Bible” of schematics as the net is too fragile a place to be sure you can come back to it.

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