Tracking Generators

[gstopp at fibermux.com]

     The technical description of a "tracking generator" would probably be 
     a "variable non-linear transfer function amplifier". What this means 
     is you could draw a graph of the output voltage as a function of the 
     input voltage, and the graph would not be a straight line but rather 
     some complex curve that can be varied by the user.
     
     A crude version of this function could be accomplished with a ladder 
     of analog comparators that in turn drive a row of voltage pots, so 
     that each input voltage level could trigger a certain arbitrary output 
     voltage. However the output of such a device would be chunked into as 
     many discrete steps as there are comparators, and any "smoothing" 
     function to round off the steps would be once again frequency 
     sensitive. Increasing the number of steps would allow a smoother 
     output, as long as the voltage values do not vary considerably from 
     step to step.
     
     Taking this to the extreme case would be best done digitally. You 
     could somehow build a table of numbers in RAM that would be sent to a 
     D/A converter, with an A/D converter on the input sweep voltage 
     controlling the addresses in the table. Now the tricky part becomes 
     the data entry human interface. With a processor (like in a 
     digitally-controlled synthesizer) it's easy.
     
     However the "interpolating scanner" concept that Juergen has 
     implemented sounds like a quite useful way to generate 
     time-independent non-linear transfer functions, using crossfading 
     VCA's to "morph" between the steps. It seems to me that you would need 
     to convert the input sweep voltage to a series of trapezoidal 
     functions that are staggered in level (is this how you do it, 
     Juergen?).
     
     - Gene
     gstopp at fibermux.com


______________________________ Reply Separator _________________________________
Subject: Re: Tracking Generators
Author:  Haible_Juergen#Tel2743 <HJ2743 at denbgm3xm.scnn1.msmgate.m30x.nbg.scn.de>
at ccrelayout
Date:    1/19/96 12:01 PM


> Could you hook a CV sequencer into an integrator?  This would be more 
> modular, if it does what you want.
     
Like all staircase / integrator methods it has the drawback of being 
terribly frequency dependant.
     
JH.