[sdiy] linear to exponential CV converter

[Derek Holzer]

And back in September there was also a big thread on this list about it 
that I somehow missed seeing before!

"linear CV to log / antilog / inverse?"

best,
d.

Derek Holzer wrote:
> 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 # 108:
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