[sdiy] Change response from Lin to Log to Lin to Exp?

[Justin Owen]

Hello,

Back to playing with VCAs again... again.

http://www.sdiy.org/juz/vca_comparison_01.jpg

This shows the response curve of the 2164 VCA (Green) plotted against the response curve of a single transistor VCA (Blue) and the same VCA with the CV inverted and biased so 0-2.5V becomes 2.5-0V - (Red) which flips the response curve.

The CV input/increase/response is Linear and is measured every 0.25V from 0 - 2.5V.

With CV of 0-2.5V the 2164 gives a nice exponential curve from 10V PP to 0 V PP.

With the CV inverted and biased the single transistor VCA gives more of a Logarithmic(?) curve.

Is there a circuit that will convert the Linear CV to a curve that would flip either of the  the single transistor VCA curves so it was closer to the Exponential response of the 2164? A Lin to ...something converter?

I'm not expecting the get a 2164 out of a 1 Tranny VCA - but I'd like to give it a shot, just for chuckles.

Thanks!

Justin