[sdiy] linear to exponential CV converter

[Derek Holzer]

Hi Andre,

Andre Majorel wrote:

> I'd like to see such a circuit. The MS-20 has linear CV for the
> VCO and exponential CV for the VCF, making proper keyboard
> tracking impossible.

Dave Manley sent me something on the MS-02 as well, which has adjustable 
Log and AntiLog amps (but yes, they are not tempco'ed). There was some 
initial confusion about what I had asked for (lin->expo=log or 
expo->lin=antilog), but we worked it out.

He also sent a National Semiconductor datasheet with info on Log and 
AntiLog amps. You can find the same circuits in Application Notes 30 as 
well, but with less explanation...

best,
d.

Dave Manley wrote:

 > A typical circuit is figure 3 in: http://www.national.com/an/AN/AN-30.pdf
 >
 > The text gives a good explanation of the circuit. You can find variants
 > of this circuit in many places.  You probably don't care if the circuit
 > drifts with temperature so R2 can just be a 1K resistor, no need for a
 > PTC.  Sub a modern matched pair if you have one, or a transistor array
 > like a 3046/3086 (or match a couple of 3904's) for the transistors..
 >
 > Another example is the anti-log amp in the Korg MS-02:
 > http://www.korganalogue.net/korgms/service/ms02/MS02schematic.jpg
 >
 > -Dave
 >
-- 
derek holzer ::: http://www.umatic.nl ::: http://blog.myspace.com/macumbista
---Oblique Strategy # 49:
"Display your talent"