[sdiy] Quantizer DAC or PWM?

brianw brianw at audiobanshee.com
Tue Dec 20 09:49:41 CET 2022

I've always had good luck with external ADC and DAC. The internal ones are "convenient" but prone to picking up noise from the processor.

I'm curious, though. With so many people talking about lowpass-filtered PWM, what's the settling time between each new value? I suppose that's equivalent to asking what the maximum sample rate. I have worked with external DAC chips that have a settling time of 35 nanoseconds. I can't imagine the time constant for filtered PWM to be that fast.

On the other hand, if you want to implement portamento, then having a voltage-controlled filter on the CV output would be a feature.


On Dec 19, 2022, at 7:19 PM, Jay Schwichtenberg wrote:
> I'd go with a 15-16 bit external high quality DAC. Internal ones usually aren't high quality. I'm not a fan of using a PWM DAC for something like this. If you want a DAC that doesn't need to be fast or precision then PWM is ok. Also use a precision voltage reference for the DAC reference, not the digital power supply.
> On 12/19/2022 1:55 PM Didier Leplae wrote:
>> If I understand correctly, the ESP32-s3 got rid of DACs but previous versions had them. I was a bit surprised not to find any
>> On Dec 19, 2022, at 4:59 PM, The SynthiMuse wrote: 
>>> Literally today, I just received my first esp32 dev board to build :
>>> https://www.google.com/amp/s/www.instructables.com/Extremly-Simple-Oscilloscope-Clock-With-ESP32/%3famp_page=true 
>>> I was under the impression that the standard esp32 had native DACs. 
>>> Am I wrong?
>>> Gerry
>>> On Mon, 19 Dec 2022, 16:14 Didier Leplae wrote: 
>>>> I’m working on developing a quantizer module for eurorack. I made a previous version using a PIC chip with a DAC which I abandoned during the chip shortage. 
>>>> Now I’m looking at taking up the project again but possibly with an esp32-s3 chip instead. This chip only has PWM, though. 
>>>> Question is whether PWM with smoothing circuit is it accurate enough for a quantizer? Does anyone have smoothing circuit to recommend? 
>>>> Or is a DAC the better option? 

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