[sdiy] Digital accumulator VCO core?

Aaron B. aaron at zadzmo.org
Tue Feb 9 20:11:46 CET 2021

On Tue, 9 Feb 2021 11:06:55 -0700
Eric Brombaugh <ebrombaugh at gmail.com> wrote:

> FPGA-based approaches mentioned earlier allow very high sample rates 
> that reduce aliases into the noise floor. There are a number of newer 
> FPGAs like the Lattice ice40 series that are inexpensive and can easily 
> hit multi-MHz sample rates with full 16-bit resolution. Using 
> all-digital PDM conversion techniques enables simple and low-cost output 
> circuits with excellent audio characteristics. I've got an example of 
> that here:
> https://github.com/emeb/up5k_basic/blob/master/src/snd.v

I would absolutely buy FPGAs preprogrammed as sawtooth-only DCOs
like this, and build analog waveshapers around them. Sounds like a good
compromise across sound quality, tracking/temperature stability, parts
count, and ease of tuning.

Aaron B. <aaron at zadzmo.org>

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