I’m working on a wavefolder and a euro rack format oscilloscope at the same time. Here is a short demo of the wavefolding shown via the arduino oscilloscope. The oscilloscope in its present configuration will only show positive signals, so I added a DC value to the output of the wavefolder. The voltages on the vertical axis are therefore not correct.
Now that is nice! Excited to see the finished products 
Cool! Always glad to see a west coast unit in progress. Is this like the Haible design? I tried to make one based on that (modified) but had no success.
The video starts with a triangle wave filtered so that it is more like a sine. Then I do some wavefolding, about half the video I turn back the filtering and do the some folding with the triangle.
I’m not sure. Any reference available?
Oh, wait-no it was this one (Elby):
No, it’s not that one.
The one I’m trying momentarily is based on 3 instances of the input signal multiplied by different gain factors. These signals are then limited by 2 LEDs or diodes connected in an anti parallel fashion. The 3 variants of the signal are then summed to form the output signal. Preceding this a DC offset pot that can be added to the input signal to shift the whole signal up or down the DC axis so that it can clip on the top side or bottom side of the wave making for more variations of the folding.
The drawing is not very clear I’m afraid. This is just my working draft. I’ll post a schematic as soon as I sorted out all the details.
I got this idea from a video on youtube but unfortunately I lost the reference.
how do you do that ?, you are like a modular building machine . its nice you set a high bar for us to keep up to but dam man …
I had a look at the video Adamski published showing a wave folding design. In his video Adamski speaks of selecting the emitter and collector resistors by using trim potentiometers:
What values did you use and what voltage is your power supply?
my power supply is 12V and put 15 k i think
i see that @EddyBergman make an article with schem and stripboard on his website
The value of these resistors do have a noticeable effect I’ve found.
i have made no test, (it’s difficult some time to me to understand in english what he said in vid)
you have test it with trimmpot ? and what values did you use ?
The circuit depends on the transistor’s Vbe and Vce which is pretty similar for all small signal transistors, and “ideally” you should provide ±1.2 V in and get ±0.4 V out, and the resistors mostly only impact the impedance of each stage (Vbe/Vce depends on current a bit, but you have to go up quite a bit before that starts to have noticeable impact).
But since you want to mess with the sound going outside the “ideal” can be entertaining. The amplifier stages may have more impact than the resistors, though.
(you can probably just poke around with your fingers and see what happens when you add your resistance in parallel with the resistors 
)
I have experimented a bit with trim pots but I have not decided on what to use yet. I guess the trim pots should balance one another so that both have the same value and the transistors operate on positive signal parts the same way as on negative parts. Choosing different values will vary the current through the transistor and depending on that I expect the gain factor of the transistor to change to a certain value. The transistors I think do the folding. But the folding I believe is introduced only for low voltage signal parts, the large signals are simply amplified. I find it a bit puzzling that the op amp stages multiply the signal by a factor of 4 and 6.8 because this must quickly lead to clipping (which is not folding). I would assume they are there mainly for buffering purposes. Now any euro rack level input signal must be attenuated quite a bit otherwise this factor 10 will drive it against the power supply voltage instantly. E.g. if the saturation pot is in its top position this will happen if the audio-in amount pot is set higher than 10% of the supply voltage (when applying a full range input voltage).
To summarize this: I’m still experimenting …
Diffrent capacitor but it still works
From the space somewhere between mignons and rack-ready modules, more polypanel-compatible mini modules:
Simple LM386-based speaker amps, for use with various noise makers. I considered populating all PCBs after testing the first build, but for some reason I used 0.1-inch spacing for the speaker outputs where 5 mm terminal blocks would have been more convenient. Might just drill an extra hole, we’ll see. Now off to print me some speaker panels.
Also in this picture, from left to right:
- Another MFOS noise maker, in progress (for use with these modules).
- Some unusually shoddy silkscreen work from JLCPCB
- The ultracheap potentiometers I ordered from Aliexpress finally arrived, so added a few of them to carriers.
Very nice - I want some of those little amp board haha.
You ever see the little amp circuit in lil sidrassi?
Down on the bottom
