1222 VCO v 1. 1/2 (eurorack)

I was designing a Eurorack conversion for the LMNC 1220 VCO and
This is the actual progression on my conversion:

Some days ago i found this thread https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module-fixes-improvements/2072 and now i have to start all over and add these fix and improvements…

My skills are very limited and I’m still in the process of “notknowing>google>study>test>fail>redo>fail>redo>success” phase. I really dont want to give up on this project but with all the fixes and improvements to add in the project i’m lost. I Already have enough parts to build 8…
I really need some help to waste less time possible and finish this project.
Anyone interested and want to help me? :smiley:

At the moment i’m studyng the possibility to amplify and regulate wave signal outs with an added TL074 buffering the signals and normalize it with resistors of different values.
Is it possible and good for this task?

Feel free to post your opinions, hints and links.
Thank you.


The biggest issue with improving the 1222 design is the PWM frequency shift, and what to do about that is, to me at least, unclear. Suggested solutions range from adding caps to a resistor between the PWM and pitch CVs to adding a -5 V regulator to Alfa’s solution with a matched transistor pair and Zener to using a different chip (the AS3340-HYB is billed as being immune, and the AS3340A chips I’ve tested seem immune too, though Alfa doesn’t claim that and I only just received an AS3340 chip to compare to; maybe I was looking for the wrong thing). There’s lots of anecdotal claims and little useful data to go on in choosing which approach(es) to adopt.

Alfa does indicate the -5 V regulator is a good idea in any case. So for now my design (for a Kosmo VCO) uses an AS3340A and a regulator. For now.

Yes. There’s some discussion of that in the thread you linked. Also see designs by Kassutronics

and Thomas Henry



Can you share the KiCad files on GitHub or something (reason I say GitHub is that it’s easier for us to contribute and make edits with your permission) so we can take a look? Sometimes a pair of fresh eyes can spot errors easier than those staring the error in the face for hours on end :smiley:


I will try to upload all on github but i’m not used to upload project on this platform…
I need to clean all the schematic and learn how to post it :wink:


If you’re new to Git, I highly recommend GitKraken. It’s a no nonsense GUI for Git that’s easy to use. It’s free for public repositories, and integrates with Bitbucket, GitHub, and Gitlab.

1 Like

Tastes vary of course. I don’t find GitKraken suits me very well. It seems very team oriented so it pushes a lot of features that aren’t relevant for me and my small solo projects. It also constantly pushes you hard to move to the “Pro” paid version. It’s not open source. A simple open source GUI that covers the basics for an individual user without all the team-related bells and whistles would be nice, but I don’t know of one.


I used to use GitHub Desktop(ughh), found GitKraken, gave it a go, and liked it. Until I found I couldn’t use private repositories, which was a real bummer as I use Git to version control literally everything in my life(I currently have 134 private repos on GitHub).

I left GitKraken aside for a while until I discovered the GitHub Student Developer Pack which gives students a free GitKraken Pro license, alongside a whole ton of other stuff(free domain names, anyone?). The only feature I use in the Pro version is private repos, the team stuff is useless to me.

I think the free version is more than capable for basic needs, and while it isn’t open source, it is well supported and comes with excellent documentation, which is why I recommend it to newcomers.

1 Like