[sdiy] simple 2164 linear to expo CV?

David G Dixon dixon at mail.ubc.ca
Wed Nov 13 22:37:22 CET 2019

Hi Neil,

All Intellijel VCOs (Dixie, Rubicon, Atlantis) use the 2164 as an
exponential converter, and they have a reputation for excellent 1V/octave
tracking.  I have been told that it can be made to track 12 octaves,
although I've never gotten better than about 8 octaves personally, which is
still more than enough for analog synths.

The Intellijel uVCA (and Quad VCA) is fully adjustable between exponential
and linear control.  These could be fed with a DC voltage to get the effect
you desire.  I believe that Mutable has a similar module.

-----Original Message-----
From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Neil
Sent: Wednesday, November 13, 2019 12:38 PM
To: synth-diy at synth-diy.org
Subject: [sdiy] simple 2164 linear to expo CV?

can a single 2164 cell be used to convert a linear voltage to roughly an
exponential voltage?

this isn't for controlling anything accurate like pitch, so I don't
think I need temperature compensation and stuff.

basically i have some already finished modules (mfos vcas and vcfs) that
only have linear CV inputs. i have a little cv output interface with a
bunch of linear faders in them that i use to control these and would
like to make a really simple 'linear to expo' CV module to use between
these so the controls feel more natural.

seems like I could just put a target DC value, say 5V into the 2164 and
attenuate that with the linear CV to get an exponential CV output?

/// Neil Harper
/// Every Wave is New Until it Breaks

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