[sdiy] SAW core VCO flyback time

David G Dixon dixon at mail.ubc.ca
Thu Sep 1 17:36:36 CEST 2016

> Totally agree here Don, but 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.

All my personal VCO designs have this "centre/edge" switch.  However, I have
to say that, in practice, I have found it to be pretty useless.

> There is still the downside of traditional hard sync, yes 
> David "interesting" is great but what if you want regular old 
> hard sync? How much hassle would it be to implement a regular 
> hard sync on a Tri core?

Not really much of a hassle at all.  The new Dixies have it.  The Rubicon
has it.  It's basically a standard resetting JFET with one small addition,
and it works well.

> If you could get regular PWM and hard sync from a Tri core 
> then it does sound like the way to go. Then for all those 
> people that love buzzy Tris they can add a pulse to get it.

A classic tri-square oscillator offers some other real advantages for FM as
well.  We have exploited these in the Rubicon.

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