[sdiy] Quantizer project.. incoming CV's switching point to change to quantized output CV's ...

Jean-Pierre Desrochers jpdesroc at oricom.ca
Tue Jul 6 16:27:38 CEST 2021

Sorry Richard but I lost you in many places
in your very detailed explanation..


So far I aim to use C scales only.

To transpose to other keys I would just change the incoming CV’s offset
with semitones steps. Primitive way to do this but easy.

Thanks anyway for your knowledge. 



De : Richard Wentk [mailto:richard at wentk.com] 
Envoyé : 6 juillet 2021 09:35
À : Jean-Pierre Desrochers
Cc : David G Dixon; SDIY
Objet : Re: [sdiy] Quantizer project.. incoming CV's switching point to change to quantized output CV's ...


I would ignore microtonal options because they’re impossible to set up and control on a device with a tiny panel, and hardly anyone uses them. 


So you get 12 steps -> oct with hysteresis on input, producing a numeric semitone + octave, through lookup tables which translate semitone + oct into various output scales. 


Don’t forget scales should be transposable. If you have semitone + oct on input that’s easy with a bit of extra arithmetic.


There are actually two kinds of transposition - modal and in-scale. 


You do one before the lookup table and one after.


Quantise -> modal transpose -> scale lookup -> scale root transpose. 



E.g. +n -> lookup to C Major -> +0 -> Various modes of major


You’re moving up and down a note range in the same scale with different lowest (‘root’) notes.


+0 -> lookup to C Major -> +n -> Various major scales


You’re selecting different major scales



Of course you can combine these options too. Voltage control of both separately is *very* useful for complex sequencing.


This looks super-complicated, but if you use C scales only in your lookup you can select different roots/modes with the transpose options. 


So you don’t need separate lookup tables for C major, D major…. C Dorian, D Dorian.. and so on. Just one for each scale type, and a bit of logic to select the transpositions.


This also works for “short” scales like Pentatonic, triads and other chord shapes, and so on.




On 6 Jul 2021, at 01:07, Jean-Pierre Desrochers <jpdesroc at oricom.ca> wrote:


This a very good point..


And the "equal voltage invervals between each note" approach
seems easier to implement in code using a lookup table with
a ‘definition’ for each scale..

This approach will effectively give a scale the same ‘luck to be played’
for all of its notes. And is less picky on the threshold voltage precision.


I’ll keep note of this. Thanks !



De : David G Dixon [mailto:dixon at mail.ubc.ca] 
Envoyé : 5 juillet 2021 19:43
À : 'Jean-Pierre Desrochers'; 'SDIY'
Objet : RE: [sdiy] Quantizer project.. incoming CV's switching point to change to quantized output CV's ...


I don't know diddly-squat about code, but I've been working on an analog quantizer with logic for generating various scales, and I must say that I'm a strong advocate of the "equal voltage invervals between each note" approach.


Of course, for the chromatic scale, this is a no-brainer: 83.33 mV per note.  However, if you want to quantize a major triad, I would use 333.33 mV per note.  For a major scale, 142.86 mV per note.  Et cetera.


Why?  Because if you are running the scales or arpeggios by playing the quantizer with a triangle wave LFO, you will want each note to last for the same amount of time.  Any other approach will impose a rhythm that will favour notes that are farther away in pitch from the others.


As usual, the right answer is the musical one, not the technical one.



From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Jean-Pierre Desrochers
Sent: Sunday, July 04, 2021 10:35 AM
To: 'SDIY'
Subject: [sdiy] Quantizer project.. incoming CV's switching point to change to quantized output CV's ...

[CAUTION: Non-UBC Email]

I'm starting a CV quantizer design and am wondering

about the following things:


Let's assume a normal quantized semi-tone scale:

All the incoming CV's are quantized to semi-tones like this:

incoming CV 'around' C, output quantized CV -> C

incoming CV 'around' C#, output quantized CV -> C#

incoming CV 'around' D, output quantized CV -> D

and so on..

12 equally spaced output quantized intervals. OK.


But if the quantized scale output is a TRIAD like

C-E-G-C-E-G-C, etc... ( 3 quantized intervals)


where are the switching bounderies of each incoming note CV's 

to change to the next outputed quantized note ?

This question is for ascending and/or descending notes..


Same question for a quantized PENTATONIC major scale output like

C-D#-F-G-A#-C-D#-F-G-A#-C, etc.. ( 5 quantized intervals)


I would think of dividing the octave range with 

equal intervals with the number of intervals

inside the actual quantized scale..

For example: 


That's 3 intervals

1 octave = 1 volt

so 1volt/3 intervals = 0.333v between each quantized notes (??)




PENTATONIC major scale C-D#-F-G-A#-C

That's 5 intervals

1 octave = 1 volt

so 1volt/5 intervals = 0.20v between each quantized notes (??)


But... I don't think that is working this way..

I think I must keep the incoming CV interval sizes

and use them for the quantized switch points.. (???)


Your opinion on that ??

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