[sdiy] Interesting blog with Roland Alpha Juno details

[John]

On Fri, 01 Nov 2024 16:45:39 +0000
rburnett at richieburnett.co.uk wrote:

> The DCO is entirely digital.  There are no integrator capacitors
> around the chip, and you can see the stepping in the sawtooth output
> on a spectrum analyser when generating really low pitch notes.  You
> can also see aliasing in the spectrum when you generate really high
> notes, but it's quite a long way down in amplitude due to the
> multi-MHz sample rate at play.

Ah, I was right the first time, then. The more you know...

Still, that means the bitdepth on the sawtooth is higher than the
Poly-800's, which is just a 4-bit ramp made by weighting the 16' - 2'
ranks it already generates. Dave Cornutt did a writeup on it years ago:
https://sequence15.blogspot.com/2013/08/how-korg-poly-800-dco-works.html