Hey guys!
First, thanks for all thanks for all your work Sam in popularizing easy-to-enter electronics and soundy-buzzy things : )
I design my eurorack and one of the first modules I wanted SSO. I experimented with some configurations and figured out, that when you touch the middle leg of the transistor (I use S9018) buzz goes down, really nice thing when I use low-capacity capacitor. However, when I tried to connect it directly to the ground it does not oscillate.
So, question is - is there any way to add a simple switch to activate second-mode of the oscillator?
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The oscillator depends on electrons sneaking through the collector-base junction when the voltage gets high enough, and continuing through the base to the other side, pulling other electrons with them and causing a chain reaction (“avalanche”) of electrons/holes that rapidly drops the effective resistance to near zero, so shorting the base directly to ground seems likely to interfere with that 
. Connecting it via a resistor might work, though (after all, your finger isn’t a ground point, it’s either a resistor or an antenna). No idea what a suitable value might be, but shouldn’t be hard to try some values (or use a pot).
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yes maybe with a pot
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Thanks guys, I will experiment next week and give feedback which values worked best for me : )
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Hi, today I’ve plugged in piezo electric thingy into middle leg of transistor (I am using “original” 2n3904).
Think the pot will be better idea but yeah - you can definitely use it for… somthing.
Mine mod looks weird, but It was fun to play and maybe I’ll use it in my project 
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Will try today and give report : )
Another question - how CV should be connected? I mean, I see 2 cables here, so for mono jack is GND and Signal, but witch is witch?
Or should I use one of them and GND as a GND for the CV?
is not for a jack directely, you must make a Vactrol (LDR + Led + resistor )
look at this for make your own vactrol (at 3.30)
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I created VCF like this - https://www.reddit.com/r/synthesizers/comments/9nkmhk/cheap_and_easy_vcf/
I through I could make one SSO with larger capacitor and use it connecting via this module module to the second SSO.
If not, purple and yellow lines are for LDR, how I should connect LED? - to the jack GND and + to the SIGNAL?
on the stripboard the purple and yellow come from the pot
you put the LDR on this purple and yellow wire (no matter for one or the other, the LDR have not polarity), with a Led at the end + a 1k resistor on + of the led, led ground to ground , and the resistor of the led on a jack + (and the jack - to gnd)
maybe a little schem it’s better (2seconds)
don’t forget to put led and ldr in black
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you can also add another pot for attenuate the CV in
i make another (bad) drawing, (another 2 seconds)
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Thanks!
I have another question. I use 5mm orange/amber LED (meter said Uf = 1.9V C=10pF) and they never light then meter is running. I connect - LED to the GND.
About your drawing - why do you suggest to use another pot? 10k, 20k, 100k?
And about the pod in the original drawing - I find out that 100K works best, it is a little higher spectrum in my opinion. Also, using S9108, if I do not input resistor between legs instead of metal wire, on the end of the spectrum seems like transistor crashes and audio is off. 22K for 100kK pot works great, 20k were to small.
EDIT: Seems like my test speaker is taking to much energy - should work with amp : )
That’s to adjust sensitivity to the CV. I would guess 10k would be best but it’d depend on the vactrol and the fixed resistor.
Interesting. When I built this with a 2n3904 and 18V I found the oscillator shut off when I turned the pot up above about 4k.
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I use +12V - I guess thats important to mention.
Today I will go with one panel 1uF, 3,3uF and 22uF, every each CV out without pot. Just to check if that have any sense and try with my another panels.
I experimented with middle leg. If I connect resistor, diode or capacitor, only to the leg - second output of the component does not go to the ground - sound changes, goes more harsh I guess. I thing going with the dip switches and connecting different values of the components may give interesting results. Maybe will try another time.
about the drawing : it’s an Attenuator pot for the vactrol, with that you can act on the voltage of your CV in (100k is certainly good, but maybe try other value)
but you can let this if you want and just do like the first drawing
some people use an Attenuator module, but personally I prefer to put attenuators directly on each of my modules
sorry I opened the post to answer, then a phone call, and after finishing my answer I saw that Analogoutput had already answered you
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SSO only seems so simple in my case, gets me furious last days : )
In my case I get sound when I connect into positive of leg output, not left leg of the pot.
So, when I added LDR and rest of the components from your drawing(this without second pot) pot does nothing. When I connected together legs of LDR accidentally, pot works fine. But as I assume, then CV will not work?
Really, have no idea why I`m having so many problems with so simple scheme - but I wanted to learn basic from the beggining.
As mentioned here and elsewhere, the SSO is really not so simple. The problem is that while the design is simple, the circuit can fail to give you your result even if you do everything right. This can be discouraging, so i advise building something else. Maybe an OSC based on a 555 like the atari punk console?
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Thanks.
I`m waiting for sockets to arrive, then will build APC according to this design:
https://www.matthewedmondson.com/atari-punk-console
Maybe this is issue with transistors I use - S9018. I will use it with +12V, so if there is any better transistor on my list please give me a note - https://docs.google.com/spreadsheets/d/1Uc5IQkfyYyc6F4a9HeAyHm1NZzXp7JpVXM0wtl_J_ik/edit?usp=sharing
LED is 5mm orange/amber LED (meter said Uf = 1.9V C=10pF).
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FOR MORE HELP WITH THIS BUILD A SIMPLE TUTORIEL STEP BY STEP HERE :
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