Hi,
I cannot figure out how to create the kind of waveshaping modulation described by BASTL in their THYME+ manual:
The on/off turning part is simple enough, but the inversion with XOR modulation I fail to grasp. I tried a lot of variants, but none of them give a scope result as in the manual. Can someone maybe point me towards the right direction? 
Thanks in advance!
I don’t think it helps, cause I am not sure. But I guess it means that one of the signals that goes into XOR is being modulated here. Well, maybe not modulated, but… modified. Cause it is a logic function, it shouldn’t output triangles, I think… So my theory is that it actually detects a slope (like delta or something), if it’s rising or falling. And then it modulates or changes the function. Before the output was 1 for rising and now it’s 1 for falling. And then it goes into XOR along with a constant +5v… and the output goes into VCA that mutes one of the section of a triangle wave and then it all goes into AM or whatever it is… So I’ll try to draw it in paint. (made a mistake there. So… in the XOR section the dotted line is actually what is being passed through here and the solid line is muted)
So yeah, I am not sure at all. Why is it XOR and not AND… I don’t know. I heard that XOR sounds like a ring modulator and that might be a lead. But I am pretty sure that XOR doesn’t output traingle wave, cause it is a logic function, so it probably modulates the signal that modulates the triangle wave… Yeah, that’s probably isn’t right, but that’s what I think makes sense.
Thanks for the reply! What I know is that XOR is indeed called a “poor man’s RM” and that it can be considered as a crude digital ring modulator. But I still can not create a similar waveshape effect as in the drawing of the manual. But I will keep experimenting!
Yeah… I mean, that’s not hard to emulate this waveform using the inverter or something like that, but with XOR… I don’t even know how to do it if not detecting the slope and all that stuff I already said…
Have you tried contacting the Bastl about it? They can give the definitive answer, haha. Even though it might seem like a small question, I would say - go for it!
Ha! I will try this and let you know!
I managed to slant the top segments to until 90°, but not in reverse (and not with XOR, lol)
see the yellow track
to do what you have in mind I think we need to track’n’hold the value of the “easy” (red) part (as above) and be able to rectify the wave compared to the point that white and red tracks intersect (I guess my white track is the same as the XOR logic, but more precise to look at in this environment)
I think I manage to do that with slope detector and logic and vcas BUT the scopes in VCV Rack gives us fake results because of samples loss with cables, with physical discrete devices and a proper scope (that works in MHz or even GHz) we would get a correct result
you are correct
that’s what’s inside the MS-20: a “fake” ring mod (which sounds lovely btw)
I will experiment with this, thanks!
Another -rather complex- experiment I did last days was:
analog → digital conversion
“flipping” bits (the xor part)
digital → analog conversion
Or use the rabBIT module of BiDoo where you can reverse/flip a bit with a button.
I did not get a clean result as drawn in the picture, but it was interesting enough to pursue.
All dac/adc modules in VCV are 8-bit. I wonder if I get better results with higher bits… which means I have to find a way to patch a 12 or 16bit encoder/decoder.
Anyway… thanks!
Here is a smaller version using only one polyphonic VCO Lab, with a cross fade to smoothly transition between the two shape extremes. I don’t understand how the Bastl Thyme treats the mid shape position, or how it transitions. But at least this provides something.
Bastl Thyme Shape 3 v2.vcv (4.6 KB)
