[sdiy] CV/Gate delay project..

Roman Sowa modular at go2.pl
Fri Jan 29 22:12:06 CET 2021


Few years ago I have selected MAX11100 for very similar application like 
this.
Cost me 5.41EUR for single. INL 2 LSB, quite acceptable. Comes in MSOP10.

Or you could try to make SAR ADC in software, using the same DAC as for 
output. This way you will never have any gain and offset issues to 
consider. Even linearity of the DAC will be not important then. And at 
requested 1ms sample rate it should be doable. Although I'm not sure if 
discrete solution like that can work better than any integrated 12-bit DAC.

Roman

W dniu 2021-01-29 o 20:18, Jean-Pierre Desrochers pisze:
>
> >Don't look for shortcuts when it comes to CV. Get decent 16 bit 
> ADC/DAC. They are dirt cheap now.
>
> Any ADC chip suggestions ??
>
> At Digikey, the cheapest 5v supply DIP 16bits ADC is Maxim’s 
> MX7705EPE+ 
> <https://www.digikey.ca/en/products/detail/maxim-integrated/MX7705EPE/1302785>at 
> $15.09US each
>
> 16 bits DAC’s are cheaper..
>
> JP
>
> *De :*Roman [mailto:modular at go2.pl]
> *Envoyé :* 29 janvier 2021 13:48
> *À :* 'SYNTH DIY'; Jean-Pierre Desrochers
> *Objet :* ODP: [sdiy] CV/Gate delay project..
>
> Don't look for shortcuts when it comes to CV. Get decent 16 bit 
> ADC/DAC. They are dirt cheap now. And I mean decent, because many new 
> 16bit converters have 13-bit linearity  and sometimes even only 10-bit.
>
> Might be a challenge if you require THT though.
>
> Roman
>
>
>
> ---- Użytkownik Jean-Pierre Desrochers napisał ----
>
> Hi list,
>
>
>
> I'm working on a new module for my DOTCOM modular.
>
> It would memorize incoming CV's and Gate's state for 2msec up to 10sec
>
> then spit the stream in steps of 1msec.
>
> The code for Gate memorizing is done.
>
> I'm now wondering if using a Microchip PIC 10bits ADC is
>
> linear enough to read incoming CV values (0 to 8vdc)...
>
> There will be an input buffer amplifier that will take care
>
> of taking down the 0to8vdc to 0to5vdc for the PIC.
>
> Incoming CV's 0-8vdc, 12 semitones/octaves.. that makes 1024 / (8 x 12)..
>
> around 10 steps between each semi-tones.
>
> My worry is the PIC ADC linearity precision..
>
> The 10bits memorized values will be output using a 12bits SPI DAC.
>
> I have a bunch of old PIC16F88 that I want to utilize here.
>
> Old but still usable for SPI.
>
> What do you think about PIC's ADC linearity wise ?
>
>
>
> JP
>
>
>
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