AW: VCO idea

Haible Juergen Juergen.Haible at nbgm.siemens.de
Fri Jul 31 12:52:35 CEST 1998


	>What you are proposing is a "piecewise linear function" PLF, if I
got
	>it right.  A sawtooth wave is feed into some black box, and a PLF
comes
	>out.  This can be done using half wave precision rectifiers HWPR. 
[...]
	>If you want a non monotonic
	>PLF (like a triangle, first up, then downwards) this means the the
	>coefficient for the first breakpoint is 0.5, and for the next it
has to
	>be -1. Remember that both coefficient outputs are added together
[...]
>  And: every segment depends on all
	>predecessor segments. It's not like drawing the waveform with the
	>mouse.

You have to use full wave instead of half wave rectifiers.
Then the segments are independent, and you *can* draw 
the waveform (with a set of sliders, not with a mouse (;->) ).
No problems with nonmonotonic fuctions. No discontinuousities
(sp ??), though.,

Shameless self promotion: 
<http://www.synthfool.com/diy/jh_ipscan.html>

For PWL applications only, you can omit half of the circuit. No VCAs,
no VCA control path, put a slider potentiometer into each of the
LED driver paths, and sum all the slider output voltages together.

I'm planning to build such a version of the IS soon. A standalone box
without VCAs to act as variable "PWL" distortion device.

	>As I said, the nonmonotonic PLF are of most interest, because they
can
	>produce really strange harmonics. 

Right !

JH.






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