A huge drop! An amazing non-3340 VCO circuit with v/oct and FM, finally with a stripboard layout!
From EB, here: https://www.eddybergman.com/2020/12/synthesizer-build-part-37-thomas-henry.html
9 Likes
What does it mean for the 2N3906s to be “matched and thermally connected”?
1 Like
Look up a little breadboardable transistor matching circuit and hook up to your multimeter to match them. Thermally connected just means they are touching and share same temp
4 Likes
Matching:
Thermal contact:
4 Likes
Matching can be done with a bag of transistors and a mutimeter. Just try to have them all at room temp and touch as little as possible.
Oh and a dab of thermal paste to hold them together never hurts
4 Likes
it is crazy how much the values change just by having them between your fingers for a few seconds . try it
1 Like
Hi I’m really a beginner and I have a question that might be a bit stupid:
I found some pcb schematics for this circuit but I don’t understand how to use them
Is it just a guide or a schema of how to use it to make your own pcb for example?
I mean I’d like to make some pcb’s like this one but I have a little bit of trouble to go from a circuit diagram to a pcb layout. I use Fritzing but my software doesn’t want to do the autorouting of the pcb so I have to put all the cables one by one and put the components in their place. that’s why I’m really wondering if it’s really useful and makes it easier to make your own pcb?
You can buy a (“authorized”) PCB at several places, just google for “MFOS VCO PCB”.
Soundtronics, ModularAddict show up on the first result page.
[Edit]
Here is the official page of this module/PCB :
http://musicfromouterspace.com/analogsynth_new/VCO20120618REV0/VCO20120618REV0.html
1 Like
Ah yes it’s sure it’s quite easy to find!
But then if I wanted to make my own was this scheme really practical or is it just if we want to print ours with a copper plate and acid?
You can build it on stripboard…
Don’t use what you posted, the PCB is double sided so it doesn’t show all the connections…
The full schematic is on the linked page.
But stripboard is nothing for me 
ok thanks a lot I think I’m going to buy one of these pcb it’s going to be easier than building the circuit on a stripboard!
Yes, easier, and you know the PCB is working because a lot of people have built it.
If you do your own stripboard layout there is a big chance you make at least one mistake which will take ages to debug… some people find that fun
3 Likes
Haha yeah personally I prefer when it works fast but sometimes you have to take your time and be patient!
Debugging IS fun, if it’s your own design !
But debugging something that has already been is not my cup of tea…
1 Like
it is sure that if the circuit which we have just built is of our coseption it is simpler to find the origin of the problem because we know well the functioning of the circuit. Whereas with the schematics of another one it is sometimes necessary to spend a lot of time to take again the circuit to understand its functioning.
For clarity, in case anyone is confused, this board is for a different VCO than the TH-555.
I’ll be building this MFOS VCO myself soon (bought the PCB). Maybe if there are further questions they can go in a new topic.
1 Like
There’s an autorouting solution that can be used in conjunction with KiCad, but I haven’t used it. As I understand it, basically autorouting really works well only if you’ve first placed all the components in good positions, and my experience is that’s about 80% of the work. (And you don’t get to be good at it without doing hand routing for a while, to learn what goes into good positioning.)
Brief experience with Fritzing leaves me thinking it’s good for making breadboard layout pictures, not so much for doing PCBs. Your mileage may vary. For me EasyEDA was better but KiCad is best. There’s a lot to learn but once I got going I found it actually easier to use.
2 Likes
It takes quite a long time to watch all of them, but for me, this DigiKey KiCad tutorial playlist explained everything I needed to know in great detail:
It would be way to overwhelming to learn without something like this, I think. I’m considering trying to make this TH-555 as a Kosmo-board once I’m done with the Arduino project…
3 Likes
It’s the “component designator view” from this page that has schematics, instructions, PCB layouts, silkscreens, etc. And points out that this is in no way a beginner’s project.
3 Likes
yes but even doing that the software crashes and shuts down so sometimes I can’t even do the routing…