So a few months after getting infected with the LMNC virus, I finally started my modular build.
I’m not even really into synths (yet, but I’m getting there, I can feel it) but I love DIY, electronics and music, so this looked like the perfect hobby.
I ordered the full Microbus kit from Frequency Central, the reasoning being that I don’t want the most crucial part (the power supply) to be my first from scratch build.
The biggest struggle was finding a not to expensive 12V AC/AC adapter.
After melting two LEDs, struggling to get the holes in the PCB open again and soldering in new LEDs, the power supply was done and worked on the first try.
The next step was the Simple CEM3340 VCO
I ordered all the parts, got the AS3340 instead of the CEM3340.
Then I built the stuff on the breadboard.
It worked on first try BUT the coarse tune was ultra sensitive.
So I did some troubleshooting.
First issue was that I forgot the 100k before the coarse tune.
So I put that in and caused the second issue: because the breadboard is so small, I shorted that new resistor to the 10n cap, so I still had the same sensitivity.
That was quickly fixed and the last issue was that I didn’t connect the 100k pot to ground because the schematic doesn’t say so.
In hindsight, I guess Sam didn’t draw it in because his frontpanel acts as ground and I could also have guessed that it’s necessarty to create a voltage divider.
So here is the core module on breadboard.
For my front panel (I’m going eurorack) I struggled a long time to find something suitable.
A week ago I found these aluminium pieces in my local hardware store.
They come in 1 or 2m long, 2mm thick and 20, 25, 30 or 40mm wide:
So I got a 1mx30mm to start and cut a piece of 128,5mm.
In the next days I’ll probably be soldering and drilling the panel.
I’ll also have to think about the future.
The next modules will probably be a VCA followed directly by a filter.
I also need to stock up on supplies.
Open question for those reading: which parts do you use in all/most projects.
Here is what I thought of getting:
I don’t think the LM324 is that popular… 5 will be plenty.
Also you’ll need 10K lin pots, they are almost as common as the 100K.
A handful of 2N3904 and 2N3906 (or the BC equivalents).
Another handful of 1N4148.
A cheap bag of mixed colors LEDs, in your preferred size (hum… eurorack… go for 3mm ).
Trimmer pots. Get a “starter pack” with several values.
100nF ceramic caps (you’ll need 2 per IC).
10uF electrolytic caps (two per module)
If you want added protection for your modules, you’ll need two 1N5817 per module.
I would go for nano’s. They are often used and dirt cheap. If you want to do some dsp then go for a Teeny or a Daisy Seed. But if you are a starter I would not buy any of that stuff until you find a project that needs them. Once you get the hang of it you’ll get the feeling what you’ll likely use in future projects you haven’t even thought of.
Can you elaborate on this part ?
I guess the 1N5817 would be connected in series with +12V and -12V to provide reverse voltage protection.
But what about the “2 per IC” and “2 per module”, what’s their usage.
@Jos Agreed, but I’m comfortable now with programming AVRs directly and always preferred the lean aspect compared to an entire Arduino. I might actually use them for other stuff.
That said I already saw some projets that use AVRs specifically, especially MIDI stuff
The caps are for power “filtering”/“smoothing”/“conditioning”/whatever people call it…
A typical power circuit for a module looks like this :
(PWR_FLAG are KiCAD’s way of telling that’s the point power enter the circuit, they have no physical counterpart)
OK, I still have BAT85 in my schematics… but in real life I put 1N5817 there, they have better specs for this job.
They are for reverse polarity protection.
The 10uF are close to the power connector.
They are a sort of energy reservoir for the whole module. Some people questions their utility as they are a big load (if you have many modules) for the power regulators, and they argue the power regs can do a better job than these caps. I don’t have an opinion on this yet
I put them in, they are easier to remove if need be than to add if nothing has been planned for them.
The 100nF are as close as possible to each IC, one pair per IC (if it’s only powered with one rail, one 100nF is obviously enough)
They also form a small reservoir per IC, and filter some high frequency noise produced by the IC out.
Sam tends to omit bypass caps especially on the stripboard layouts. In audio electronics, things tend to work more or less okay without them. But in principle they should be included and they’re almost always indicated in schematics. They’re cheap and don’t take up a lot of room, so I always use them.
The holes for the pots aren’t exactly there where I drew them and I’m not entirely sure why.
I’d guess that it’s either my very cheap drill (that vibrates quite a lot) or the fact that I went from center punch to a 3mm drill bit to directly a 7mm drill bit.
Since the panels cost me about 1,10€/piece, I’ll simply try a second one)
Even using a drill press and a step drill, my first couple of panels’ holes were alignment challenged. You’ll get there. (And that’s one thing I like about FR4 panels, I can align things to the micron in software and the fabricator will get them more accurate than I can.)
Always glad to hear my sharing is helpful…just not sure how I feel about being an example to copy from as I’m still not very sure of my own work I’m still experimenting with different footprints each time trying to figure out which really are the ones I like. Most of the ones I’m happy with I actually took from @analogoutput’s projects
I took a quick look at yours and nothing jumped out at me…but that doesn’t mean much as I’ve looked carefully over mine many times and missed errors I didn’t find until I etched the boards or soldered them.
Started another stripboard today from the @juggle github - got half the board done, hopefully finish the other side up and mount to the faceplate tomorrow.
).
I’m still experimenting with different footprints each time trying to figure out which really are the ones I like. Most of the ones I’m happy with I actually took from 
