[sdiy] Continuously variable waveshaping (was Behringer Neutron)

[Tom Wiltshire]

> On 7 Apr 2018, at 10:08, Olivier Gillet <ol.gillet at gmail.com> wrote:
> 
> If you did it under CPU control, you could probably dump the requirement for VCA linearisation too (compensate in software), which reduces the hardware by one VCA and two op-amps per channel. You can do a 4 waveform mixer with just a 2164 and a quad-channel DAC fed to a single I-to-V op-amp stage.
> 
> As a bonus, you could also control the output level, assuming you had enough DAC resolution - just turn down all four waveforms at once by simple subtraction from their DAC values (don’t you love log control?!).
> 
> I had the same idea and made the "Frames" module :)

Very nice, Olivier. I was just reading your schematic! I like the stored “frames” idea - very flexible.

I notice you used a 12-bit DAC. Assuming 100dB range on the VCA, that gives you roughly 0.024dB/bit accuracy!

Presumably that’s how you were able to implement Lin/log CV control and different easing curves in software. That wouldn’t have worked so well with less resolution.

Tom