Linearise exponential CV?

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Learning to Wiggle
Posts: 4
Joined: Wed Jun 26, 2019 2:16 am

Linearise exponential CV?

Post by mcleinn » Sun Feb 09, 2020 6:47 pm

Hello dear modular community,

my wife really likes to play the Doepfer Theremin patch I did today, but she says that the pitch scale is too
exponential (ie. the higher the pitch gets, the quicker it changes with the same amount of movement)

So what would be the easiest way to linearise the pitch CV before going into the VCO, so that changes in high
CV (as a result of the exponential Theremin controller) actually lead to less pitch change than changes in low CV,
resulting in a (more or less) linear function finger movement - pitch?

Maths 101 says I take that one can linearise an exponential function by applying a logarithmic function, but how to
do on my modular without a PC? Maybe using Maths or some custom Voltage Controlled Resistor circuit? Any
modules helping out in this (potentially allowing generic CV transformations)? I tried to google for VCAs and VCOs,
but it seems that a lot of times, when people say "logarithmic" they actually mean exponential, which makes
browsing for solutions somewhat difficult.

Thank you!

Wiggling with Experience
Posts: 448
Joined: Fri Apr 03, 2015 9:38 am
Location: East Coast USA

Re: Linearise exponential CV?

Post by jorg » Mon Feb 10, 2020 9:34 am

How about something like this?

I suspect the Theremin's curve is beyond exponential; it probably has something like 1/d behavior (where d is distance). The A-136 could tame the extreme end a bit, bending the curve toward "normal" exponential.

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