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

Mike Bryant mbryant at futurehorizons.com
Mon Jul 5 12:12:39 CEST 2021


It's not so much the number of octaves but how closely you want to get to exact ratios for non-equal temperament scales.   It is easy using linear oscillators over a limited range but assuming log VCOs then getting to exactly 3:2 ratios for all notes on a Pythagorean scale is actually quite awkward, and the ones that are off slightly really stick out.  

Also if you are using piano tuning rather than equal temperament on the keys then you need to have an accuracy of better than one cent just above A440 according to the Railsback curve, though in this case the inaccuracies can occasionally make it sound better rather than worse.


-----Original Message-----
From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Brian Willoughby
Sent: 05 July 2021 03:49
To: SDIY
Subject: Re: [sdiy] Quantizer project.. incoming CV's switching point to change to quantized output CV's ...

It depends upon how many octaves of range you want the DAC to cover.

5 octaves (5 V) with 12 bits gives 1.46 cents per step ... if I did the math correctly.

There are some 14-bit DAC chips if you don't think you need 16-bit accuracy, but sometimes the price is less for 16-bit due to supply and demand.

Brian


On Jul 4, 2021, at 16:30, Mike Bryant <mbryant at futurehorizons.com> wrote:
> I'd personally recommend a DAC with more bits as this allows you to implement non-equal temperament scales more accurately.  For example in Pythagorean tuning do you accept 702 cents as being good enough for the 3:2 ratio, or do you want it dead on.  
> 
> -----Original Message-----
> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Jean-Pierre Desrochers
> Sent: 05 July 2021 00:19
> To: 'Brian Willoughby'
> Cc: 'SDIY'
> Subject: Re: [sdiy] Quantizer project.. incoming CV's switching point to change to quantized output CV's ...
> 
> I agree with you Brian.
> Yes, the use of dead zones are necessary around the threshold points to  avoid any glitches on quantized output..
> I think my PIC micro's  10bits A/D would be Ok to read the incoming CV signal.
> The quantized output though will be from an external SPI 12bits DAC.


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