Tom Henry Tunable Noise Source

WeAreAs1 at aol.com WeAreAs1 at aol.com
Fri Nov 12 22:01:50 CET 1999


In a message dated 11/12/99 12:44:19 PM, you wrote:

<<Cool! Is there user-controllable filtering of the noise that is used to
modulate the VCO? If the noise is processed by a lowpass filter before
FMing the VCO, the cutoff frequency of the filter will control the
"width" of the noiseband, while the VCO frequency will control the
center pitch of the noiseband.>>

I don't have the circuit drawing to look at right now (I just briefly glanced 
at it at a newsstand), but it may have had some kind of general 
fixed-frequency, fixed-slope lowpass between the amplified noise transistor 
and the VCO.  However, it definitely did not have any kind of tunable filter 
in that path - but that would certainly be a useful addition (or at least put 
in some kind of patch point).  An adjustable-Q bandpass filter might even be 
more useful than the lowpass in this regard.  You could have both the filter 
and the VCO track your pitch CV for an even more dramatic "pitched noise" 
effect.

Michael Bacich




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