MOTM

I've heard that it is difficult for a VCO to create a sine waveform
(or really a good quality sine wave).  Is this true and why is it 
so?  Its obvious to me that it would be harder to generate a sine 
wave in comparison to a square wave, but what is specifically 
challenging theoretically and in practice?

Some people complain about the purity of sine waves generated from 
VCOs.. does this matter to you?  Do you find sine waves useful in 
subtractive synthesis or could you do without this waveform?

Can't say much about how hard they are to produce, but I would imagine that it's not easy to get that "perfect" curve shape in the analog domain.  Digitally it's easier, since you can just use a DSP to perform a mathematic function.

Are sine waves useful?  You bet.  Great for re-enforcing bass.  In terms of purity, well, I haven't compared any, so I couldn't tell you.

--PBr

-----Original Message-----
From: foraxx [mailto:omgemag@...]
Sent: Monday, September 22, 2003 3:46 PM
To: motm@yahoogroups.com
Subject: [motm] Sine Waves


I've heard that it is difficult for a VCO to create a sine waveform
(or really a good quality sine wave).  Is this true and why is it 
so?  Its obvious to me that it would be harder to generate a sine 
wave in comparison to a square wave, but what is specifically 
challenging theoretically and in practice?

Some people complain about the purity of sine waves generated from 
VCOs.. does this matter to you?  Do you find sine waves useful in 
subtractive synthesis or could you do without this waveform?

Yes, even the mighty 300 doesn't produce a pristine sine wave.  There 
are some harmonics produced, even in a finely scope-tuned 300.  In 
practice, for adding beef in the sub-bass region for e.g., this isn't 
much of a problem.  But if you really want pure sine waves, any of 
the MOTM filters will oscillate and the 440 in particular tracks well 
over an octave or so (perhaps more).  For nice bell tones and ring 
mods, I use oscillating filter output.

Mike

--- In motm@yahoogroups.com, "foraxx" <omgemag@h...> wrote:

> I've heard that it is difficult for a VCO to create a sine waveform
> (or really a good quality sine wave).  Is this true and why is it 
> so?  Its obvious to me that it would be harder to generate a sine 
> wave in comparison to a square wave, but what is specifically 
> challenging theoretically and in practice?
> 
> Some people complain about the purity of sine waves generated from 
> VCOs.. does this matter to you?  Do you find sine waves useful in 
> subtractive synthesis or could you do without this waveform?

The common method for generating a sine output from a VCO involves 
taking the native waveform that the vco generates (usually a 
sawtooth), then deriving a triangle (often with a small notch at the 
peak), then using the derived triangle to drive a CA3080 into the 
nonlinear region to approximate a sine wave. The key word here 
is "approximate". It is not that pure. An oscillating VCF, however, 
can generate a very pure sine wave. When I do FM and cross linked 
chaos patches, I generally get better results when both modulator and 
modulatee are oscillating filters.

Moe


--- In motm@yahoogroups.com, "foraxx" <omgemag@h...> wrote:

> I've heard that it is difficult for a VCO to create a sine waveform
> (or really a good quality sine wave).  Is this true and why is it 
> so?  Its obvious to me that it would be harder to generate a sine 
> wave in comparison to a square wave, but what is specifically 
> challenging theoretically and in practice?

What he said :)

--- In motm@yahoogroups.com, "mate_stubb" <mate_stubb@y...> wrote:
> The common method for generating a sine output from a VCO involves 
> taking the native waveform that the vco generates (usually a 
> sawtooth), then deriving a triangle (often with a small notch at 
the 
> peak), then using the derived triangle to drive a CA3080 into the 
> nonlinear region to approximate a sine wave. The key word here 
> is "approximate". It is not that pure. An oscillating VCF, however, 
> can generate a very pure sine wave. When I do FM and cross linked 
> chaos patches, I generally get better results when both modulator 
and 
> modulatee are oscillating filters.
> 
> Moe
> 
> 
> --- In motm@yahoogroups.com, "foraxx" <omgemag@h...> wrote:
> > I've heard that it is difficult for a VCO to create a sine 
waveform

> > (or really a good quality sine wave).  Is this true and why is it 
> > so?  Its obvious to me that it would be harder to generate a sine 
> > wave in comparison to a square wave, but what is specifically 
> > challenging theoretically and in practice?