[sdiy] Imperfect VCO

[Don Tillman]

   > Date: Fri, 1 Aug 2003 09:40:54 -0700 (PDT)
   > From: Tim Ressel <madhun2001 at yahoo.com>
   > 
   > It occurs to me that a perfect sawtooth is a very
   > unnatural thing. It's the quest for that nanosecond
   > reset time that is causing all the problems. Do we
   > really need harmonics that extend into the amateur
   > radio bands? 

Slower reset times cause tuning problems (due to the time spent on the
reset), and also cause a glitch when you're deriving a triangle wave
from the sawtooth.

The Rhodes Chroma VCO is a unique design with a charge pump circuit.
It has long reset times, no triangle wave, and great tuning accuracy.
And it sounds very nice.

   > Having slayed the reset dragon in my own oscillators, I'm now
   > wondering if what we really need is a triangle oscillator that
   > can vary its symmetry over a wide range without changing
   > frequency.

http://www.till.com/articles/VariableSaw

  -- Don

-- 
Don Tillman
Palo Alto, California
don at till.com
http://www.till.com