[sdiy] SAW core VCO flyback time

[Tom Wiltshire]

On 31 Aug 2016, at 21:57, Richie Burnett <rburnett at richieburnett.co.uk> wrote:

> If you're generating your PWM from a perfect triangle waveform, then the resulting PWM waveform doesn't have any pitch modulation because it's leading and trailing edges are modulated equally and oppositely.  However, any sub-oscillator divider that triggers off either edge would suffer some pitch modulation.  I guess the easiest way to mitigate this would be to just drive the sub-osc divider from whatever logic in the tri-core that periodically switches the direction of integration.

Or use schmitt-trigger-input CMOS and run it off the ramp!

Actually, the SH-101 runs the sub-osc off the ramp, but it uses a transistor to pull the input of a 4013 bistable down to ground. This was clearly a deliberate decision by Roland, since they have the variable width pulse available right next door.

Tom