[sdiy] SAW core VCO flyback time

[Tom Wiltshire]

On a ramp wave, the pulses get wider in one direction only, whereas with a triangle, they get wider in both directions symmetrically.

In the ramp wave case, this means that there's a phase shift going on. And a changing phase shift is a frequency modulation, so it warbles.

At least, that's my understanding of it. If that's not right, perhaps others can correct me.

Tom

On 31 Aug 2016, at 19:25, rsdio at audiobanshee.com wrote:

> Could someone describe "that lovely PWM vibrato sound" for me? I'm mostly asking why it's possible with sawtooth and not triangle.
> 
> A comparator can turn a sawtooth or triangle into a square. With LFO on one input of the comparator, you can get PWM from either sawtooth or triangle on the other input. The only difference would seem to be the sensitivity, but LFO amplitude should solve that.
> 
> What am I missing?
> 
> Brian
> 
> 
> On Aug 30, 2016, at 11:33 PM, Andrew Simper <andy at cytomic.com> wrote:
>> ... one thing left to talk about is PWM. I have noticed that on a lot of Tri cores the Sqr is derived from the Tri, not the Saw, is there any reason for this? If you use the Tri you can't get that lovely PWM vibrato sound. In fact perhaps even have a switch so you can pick between Saw or Tri for the source of the Sqr.
>> 
>> If you could get regular PWM and hard sync from a Tri core then it does sound like the way to go.
> 
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