[sdiy] Analogue Drift (was Re: HF VCOs and tracking problems)

[Ian Fritz]

At 08:46 AM 11/14/2012, Dave Manley wrote:
>"I recently built my first digital oscillator (whoa!) " Whoa!!!!???? 
>OK,  has to be a story here.  Details please.  :-)

Not much of a story, really.  After the Blue Lantern affair I decided to 
spend most of my time on projects for myself.  One of the first was to have 
a different look at digital wave generation.  It never made sense to me to 
be using subtractive synthesis and traditional waveforms because of all the 
aliasing issues.  But over the years I spent working on chaos theory I 
noticed that limit-cycle oscillations (multi-periodic waves in non-linear 
dynamic systems) have a wide variety of interesting sounds.  So I thought 
to try digital generation of this type of waveform, along with timbral 
shaping by parameter variation.  With a lot of help from Scott G. and Eric 
B. I figured out how to do this in Verilog using iterative methods 
(Runge-Kutta method, etc, for integrating systems of non-linear 
differential equations).  So it was a big deal for me to get a Sin wave 
this way. Not the best way to do a Sin wave, of course, but it sets me up 
for further work

Ian