[sdiy] Generating a large number of CV outputs

[brianw]

Yes, I mean mux applications, but also any DAC output needs reconstruction filtering if you want to avoid aliasing. There are some delta-sigma DAC that are oversampled and attempt to perform most of the reconstruction filtering in the digital domain, but a DAC without this oversampling and filtering will need a reconstruction filter whether it's mux'd or not.

I've recorded enough live electronic music performances to know that there is a surprisingly large number of commercial products out there with digital-to-analog conversion that has insufficient reconstruction filtering, as evidenced by the horrible aliasing. Granted, you have to record higher than 44.1 kHz to see this, since most DAC hardware is running at least that sample rate or higher.

Comparing a multi-channel DAC implemented via FPGA implies that each output is dedicated and has its own pulse-smoothing filter. At that point, you already have significant filtering components.

Brian


On Dec 10, 2023, at 4:03 AM, Mattias Rickardsson <mr at analogue.org> wrote:
> Den sön 10 dec. 2023 00:52brianw <brianw at audiobanshee.com> skrev:
> > 
> > Personally, given the long history of DAC and CODEC designs, I strongly recommend against designing your own converter. These filtered pulse solutions have much longer settling times than the 8-nanosecond setting time of that 125 MHz current output DAC (from Texas Instruments).
> 
> Here you only mean for mux-ing applications I presume? That's where it's important with fast settling. 
> 
> If you'd build a multi-channel DAC using an FPGA, the settling behavior of your homebrew solution wouldn't be as much of a problem.