Have finished my first two Kosmo modules, the first was a clone of the CR78 bassdrum, that I mentioned earlier, the second is a master clock generator with 8 divided outputs: ÷2 to ÷256, it also has an ext clock, gate and reset inputs and a CV input that provides a limited degree of variation of the clock speed (using pin 5 of a 555 being used as the clock generator)
Iam about halfway through a third module a utility module with power input, passive multiples and 2 passive attenuators. Will get photos posted soon!
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Now all working, except one of the 3350 filters - awaiting a new chip which should be here Monday. Then I can close it up and do some proper demos.
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Metallic Chaos (Metal-o-tron) from @illucynic is up and running. This thing is weird and fun, as a module should be.
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Woah, haven’t seen that before… sound demo please?
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That video only hints at what you can get out of this module. It would take a very long demo to go through all sounds.
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V1.2 of Distortion VCF. This time I tried balsa wood for the panel, and since I had more space, I soldered several components “point-to-point”.
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Nice.
I like that you added a switch to select between diodes or LEDS. Does it make a big difference to the sound?
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There is a notable difference in the volume drop when the gain is cranked up, as the 5mm red LED’s have a forward voltage of ~1.8V compared to the ~0.65V of the 1N4148. A higher the forward voltage means that there needs to be more signal for the diode to start conducting and to clip the signal. More clipping means more distortion, compression, and volume drop. Apart from the difference in the amount of clipping based on their forward voltage, diodes also exhibit a difference in the softness of their clipping based on the whether changes in the current lead to changes in the forward voltage. Unfortunately, these are very subtle differences when it comes to simple waveforms that do not vary in their dynamics. In a dynamically played guitar, however, the difference is considerable.
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The same hobby shops that carry balsa also carry the much sturdier Bass Wood (I can’t make this stuff up!), which is available in the same thicknesses as balsa. Bass wood is heavier than balsa. Unless you intend on flying your modules, the extra strengh is a bonus.
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Final VCF chip arrived today, so it’s all done and ready for handing over to my brother.
Here’s a pic:
And two contrasting demos… a poly thing and a mono thing, both just ZOA running midi into it.
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Next on my list of simple/basic modules was a clock. I looked for schematics for a simple 555-based clock, and after browsing through the schematics by Gerbrand Sterrenburg (aka Gerbster), Syntherjack, Steffen at “Bumm Bumm Garage”, and R.A. Grockett Jr. in an old article in Polyphony magazine, I settled on the Tick/Tock module by Circuit Abbey (which has since gone offline but you can find archived here).
As I’ve ran out of toggle switches, I used a small DIP switch that I had around, and wired it on a little panel that will live in a small box along with other 9V modules.
The DIP switches activate a couple of capacitors for the following range:
~0.13 to ~4.3Hz
~0.14 to ~4.7Hz
~1 to ~43Hz
~14 to ~480Hz
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Classic, straight forward, well done!
In addition to dip switches you can use 3 header pins and a jumper as a toggle switch.
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Its been a while since I posted my last update. I’m super happy with my new solid oak case. Since I don’t nornmally do woodworking, I was kinda stuck on that project until I received some help from a friend who had the right tools. 
I basically made two cases that I could possibly connect together with seperable hinges and latches in order to be able to move them, though it won’t be a super portable setup.
I designed some power busboards myself and then realized I forgot to put filtering caps on them 
. So for both cases, I bought a proper power bus board from modular synthlab and also added an extra one that I made myself to have room for 27 modules.
Some pictures:
In the meantime I got some synth gear. A Roland TR8S and a Korg SQ1. I still have to learn how to get the most out of these and will need a proper audio mixer as well.
here are some jams for you to enjoy! I hope to record some tracks someday.
Next up, I want to build a clock divider, a quantizer and learn PCB design so I can build a few more VCO’s. I like playing with multiple synth voices and using more oscillators per voice.
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I have yet to see a cogent explanation of what capacitors on a bus board are supposed to do. For instance this design, the first one my search just turned up, no other reason for its choice:
You call them “filtering caps” but a capacitor by itself doesn’t filter: For a filter you need a resistor too. And here there are no resistors accompanying the capacitors. (There are resistors but they’re current limiting resistors for the LEDs.) So the caps aren’t filtering anything. Instead they appear to be intended as bypass capacitors.
But the whole point of bypass caps is to sit near the ICs and supply them with current when their need spikes. These caps are miles away. In between, on the module PCBs, there almost certainly are similar size bypass caps much closer to the ICs. So these bus board caps seem useless as bypass caps too.
So… what good ARE they?
No one’s ever given me a better answer than “well, they can’t hurt” and even that is not obvious — they’ll add to inrush current, for sure.
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I’d always assumed they had a similar role to ‘filter’/smoothing capacitors in amps that condition the rectified power supply, meaning the DC you send off around the amp isn’t noisy and you’re minimising hum. Those caps fail, are you’re guaranteed 50/60 cycle hum.
But I don’t actually know if that’s right or required in a modular build.
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Maybe. I don’t know anything about amps though. I know in a linear PSU you have smoothing caps, and you don’t have resistors, but they come after a rectifier diode. Without a diode or a resistor, it seems to me you’re connecting the caps directly to a voltage source, and by definition of a voltage source they can’t affect the voltage. Of course in the real world there aren’t perfect voltage sources, so maybe there’s something going on I don’t understand.
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I think you’re right about the caps on a bus board being redundant. If it’s not part the linear power or next to the ic of a module the only benefit of capacitors in the bus is to stress test your modules as you power up. If in doubt - leave them out.
I like to think of these kind of caps as little reservoirs of charge that can dump current where it’s needed quite fast, while the regulator might struggle a little with peak current draw. The regulator charges the reservoir at a kind of steady rate and then the reservoir can handle any spikey current peaks that may be required.