Another CD40106 osc
and also a more complex old project with a 555 osc / a CD40106 osc/ seq CD4017 / filter clone MS20 / LFOs / sync …
controled by an external clock (my first gate seq and stylophone beat box hack)
it was fun 
behind here’s some spagghetti !
when i look to the mess in old circuit 
, i see that it’s really better clean now !!!
Analogue LFO. Just needs a piezo pickup or an electret Mic and preamp added.
I used to use either stiff card from a discarded cigarette packet or even an ice lolly stick. The latter tended to fail at low rates when the stick fell out of the back fork.
excellent ! me a piece of cardboard and a clothespin 
awesome! I was looking for a small and easy(ish) synth to gift a friend and this looks like the perfect option! I also have most if not everything needed so it’s extra perfect hahaha
if you have some questions …
I have a 8038 and a 2206 chip. Has anyone seen or even used these as proper v/oct vco?
For the 2206 there is Thomas Henry’s design :
It’s 8038 design isn’t V/Oct but linear :
Thanks Eric, I think I’ll build these…some day.
I am working on this VCO design on the last couple of weeks. My goal was to have a simple schematic with low count of components which are broadly available and not too expensive and 1V/oct tracking. This is what came out and I am actually very happy with the result.
The oscillator core is based on the schematic from the Jupiter 8 but with up-to-date components. I replaced the current sink by a simpler version and made it optional to use two matched transistors or one BC847BS. I built a few versions now with the BC847BS and tracking over the whole range of my Beststep Pro is very good.
So components per VCO are only a few bucks and I am currently working on a PCB layout with eight oscillators on it.
Feedback on this is very welcome!
Nice! Do you have a link to a source for the polypropylene cap?
I usually buy my stuff at Reichelt here in Germany, I use this one: https://www.reichelt.de/folienkondensator-1-0nf-63v-rm5-fkp2-63-1-0n-p172404.html
You might get away with some other film capacitor but I assume tracking over the whole range won’t be that nice.
Whaaaat, this is so awesome. How do you even go about starting a project like this?
You gotta give it a name!
I wanted a simple VCO with good 1V/oct tracking at the lowest price possbile. Many of the existing designs use parts that are hard to source or are very expensive (or both), eg. tempco resistors, pre-matched transistors, fancy op-amps etc. or are too complex. Also integrated circuits like the AS3340 are too expensive with the sourounding circuitry for my taste. The idea was always to have a board with many of these on it so it needed to be as inexpensive as possbile. I looked at schematics from polysynths from the early 80s and read the relevant websites on these topics and this came out. I think this is a good compromise of tracking quality and price, components are less than 4 euros when I buy them at a german retailer.
It already got a name, it’s the Polykit VCO. This will be the first in a series of schematics and PCBs in the same fashion. I will release all the stuff on Github when it’s ready.
noob question:
Gerbers are what I can use to print my own board from scratch correct? I bought some copper clad boards and ferric chloride from the Microcenter and wanted to give this a go.
LM358
