[sdiy] VCO - sine output - why bother?

[David G Dixon]

To answer Quincas's question below:  It is relatively hard to make a sine
wave directly without using a self-oscillating filter or a digital
wavetable.  It is harder to get superior tracking in a filter than in a
well-designed VCO.  Also, it is pretty hard to shape a sine into anything
else, because it has no sharp edges or straight lines.  It is very
straightforward to shape triangles or saws into the other waves with
rectifiers and plus-minus amps, which are easy to design.
 
Also, a sine shaper to get a sine with a THD of about 0.5 to 1.0% is
convenient and cheap.

I have another question about the sinewave issue (btw I love my sines, use
them all the time, but only the filters in oscillation give me perfect
sines)
Is there not a way to make a sine core oscillator and derive the other waves
from it? Like a filter with fixed high resonance for the sine, a comparator
for the square etc...
Why doesn't anybody do that?

Quincas Moreira  

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