#muvco — Public Fediverse posts

Was laying out the #kicad #schematic for #muvco and it started to seem too pedestrian.

Went back and realized I had been using the #pcm5102 wrong and it does indeed do exactly what I originally wanted.

Now making a waveform generator instead of using the dds #ad9833. Much more flexible in shape and can be semi-polysynth ("chordal #synth"?) #synthdiy

Can now generate a perfect 5th in 260us! In mostly-unoptimized #micropython! Just dyads still--need to generalize to larger chords + diff shapes.

Ugh, there's a problem with the through-zero linear fm "just flip the phase 180" idea for #muvco.

#AD9833 works with a phase accumulator. Meaning it just counts up in a ramp at a rate given by the freq. Then it adds the phase register.

When I flip to the other phase register, it's a discontinuous jump = an audio pop.

Can't count backwards. Don't know where I am in the phase (I think) so I can't just add 180 to that (the #math way)

Maybe just a low-pass #filter to drop the pop?

#synthdiy

I threw an FM knob on the #muvco just b/c I thought I oughtta. Getting to that part now, it looks like I'd prefer linear FM with "through-zero"

Conceptually, that's really simple to add purely in software with the #esp32 + #ad9833 b/c it has two phase registers. Init them to 0 and 180 and flip when the frequency sign toggles.

Hopefully takes just an hour or two today. Then I could hook the VCO into existing VCF/VCA #eurorack modules and retry Bach a little more musically.

Well, #adhd did it again. Right now my Interest List is:

- #muvco
- assemble mixer pcb that came back last week
- read #midi files
- two voices
- think about low-part-count implementation idea for #polysynth #synthdiy
- work on #geometricalgebra problem sets (from good-so-far book: https://geometricalgebra.org/)
- take birthday present manim course (https://www.manim.community/, but more than basics)
- read Empire of the #Ants and #DawnOfEverything

That on top of a real job and a #honeydew

Fixed ramping on #synthdiy #microcontroller #micropython (#python) #muvco by eliminating high-pass input on CV. Had a mess on the front end and now have a theoretically correct and practically simple setup

Now to fix #ad9833 output--still a mess of ideas. One problem is it outputs <1V for sine and triangle but 5V for square. Fortunately you can't really clip a square, so I can slam everything to 12V and then scale down

One opamp to scale and bias, another to reinvert and unslam...?