2 VCO's - 1 Log convertor (polysynth design)

[Tony Clark]

>   OK, crazy idea... Im trying to build my polysynth, it has 2 VCO's per 
> voice, but what Im wondering is , does anyone know a way of driving 2 VCO's 
> (usual ramp/square) from one log convertor, essentially they will play the 
> same note, but one may be detuned from the other... I had though of messing 
> with the reset level on the ramp generator, but this will affect the level 
> of the 2nd VCO.

   I assume that you can achieve what you want by using a three 
transistor current mirror, where you have your typical one transistor 
front end, but then two outputs (two transistors in parallel but with the 
outputs individual, one into each VCO comparator).  I imagine that for 
this to work, the two output transistors should be _extremely_ well 
matched.  :)
   However, how could you then separate the tuning of your VCO's?  You'd 
lose the ability to detune (except by changing the reset level of one 
VCO which would also affect that VCO's output level) or have fifths/octave 
separations.  Seems like a bigger negative than dealing with the added 
parts count, IMO.

   Tony

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I can't drive (my Moog) 55!         |     The E-Music DIY Archive
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