[sdiy] SAW core VCO flyback time

[Ian Fritz]

My take on this is totally different.  I generate as clean a Saw as I 
can then feed it to my Snicster shaper.  This unit tilts the Saw 
continuously until it is a Tri. From there various waveshapers, such as 
the 5Pulser and the Wavolver can be added.  With this approach the Tri 
wave is somewhat restricted, since it will always generate waveforms 
with odd-only harmonics.

Ian


On 8/29/2016 1:09 PM, Donald Tillman wrote:

> While deriving the standard waveforms from a triangle core is a little more tricky, there is a very interesting advantage.
>
> With a sawtooth core, the triangle is derived from the sawtooth by sending it through a full wave rectifier circuit (or call it an absolute value circuit) which folds the bottom half of the sawtooth up to the top.  The original sawtooth is sharp and pointy, and has a finite reset time, and the transitions can show up as glitches.
>
>>From a wide angle view, the saw->triangle shaper is taking a sharp pointy wave with a lot of harmonic content and making it into a less pointy wave with very low harmonic content.  A sawtooth wave has 39% harmonic content by power, and a triangle wave has 1.5% harmonic content by power.  And because there's so little harmonic content in the intended triangle wave, any faults will stand out for all the world to hear.
>
> But if you do it the other way, start with a triangle wave core and derive the sawtooth, any glitcheroos in the process will be swamped out by the regular harmonic content of the sawtooth wave.
>
> So the triangle->saw converter has math and psychoacoustics very much on its side.
>
> Practical result: you can hear differences between VCO implementations much better by listening to the triangle waves.
>
>   -- Don
>
> --
> Don Tillman
> Palo Alto, California
> don at till.com
> http://www.till.com
>
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