[sdiy] Generating a large number of CV outputs

[Eric Brombaugh]

I did a PDM 16-bit stereo audio output with a low-end FPGA a while back 
and it worked pretty well - resolution and THD were both excellent. I 
could easily see extending that to many independent outputs, but I agree 
that absolute DC accuracy would likely be a challenge requiring careful 
electrical design and calibration at mfg time might be necessary.

Eric

On 12/7/23 18:21, Matthew Skala via Synth-diy wrote:
> On Thu, 7 Dec 2023, Danjel van Tijn / intellijel wrote:
> 
>> Let's say I wanted to generate 100 outputs with an update rate of a few kHz
>> and an equivalent bit depth of 12 or 16 bits.
> 
> Which is it, 12 or 16?  You've got your work cut out for you if you really
> want 16-bit absolute DC voltage precision on even one output.  The number
> of outputs isn't your biggest concern when that's a serious goal.
> 
>> Now that DACs are cheaper, is it better to chain a bunch of 8- or 16-channel
>> DACs?
>>
>> Or would it make more sense to use an FPGA and create a giant multi-channel
>> 1-Bit DAC?
> 
> Using an FPGA is going to require you to solve for yourself a lot of
> problems that would be solved for you if you used ready-made DAC chips.
> I wouldn't be eager to do that.  I also don't think 1-bit DACs are
> well-suited to generating precise DC voltages; as I wrote at length in my
> recent Web log series (https://northcoastsynthesis.com/news/dacs-and-bit-count/
> et seq.), they reproduce signals, not voltages.
> 
> However, if you do put in the effort to make it work, the FPGA would
> probably be cheaper.
>