[sdiy] Chris Synths polysynth

[Tom Wiltshire]

Here’s the correction:

Imagine you have a DAC with 4-bit resolution. If we use one with a step-between-values of 1V, and then add the output of another with a step-between-values of 1/16th of a volt, we can make an 8-bit DAC. That’s basically what you do with the PWM. The process is helped by the very good linearity of digital-counter-based PWM as a method of producing a voltage.

I’ve used a 3-bit PWM scaled to produce 1V per step and a 4-bit PWM scaled to produce 83mV per step to produce Pitch CVs. It worked very well and produced good CVs across the 8 octaves. The reduced bit depth of each PWM DAC means that the output frequency can be higher without the PWM clock frequency having to be super-high, and this improves the effect of filtering and the responsiveness of the CV to changes.

> On 21 Oct 2021, at 09:54, cheater cheater via Synth-diy <synth-diy at synth-diy.org> wrote:
> 
> Correct me if I'm wrong, but I think summing two PWMs will just add 1
> bit of depth.