how to convert log to linear voltage

[danjel]

I am getting confused by the math and terminology on this:

I have a VCA chip (THAT 2162) that has exponential gain control. This means that linear changes of voltage result in exponential (dB) changes in volume.

This is great but I also want to be able to switch to a circuit that will allow me to linearly control the gain as well. So in this case, how do I process a linear control voltage so that it causes the exponential gain control to change linearly.

Do I need a log converter circuit?

 

[MikeMl]

or two pots, one with a linear taper, and the other with an "anti-log" taper (log taper mounted upside down???)

 

[danjel]

I should have been more specific that I want to control it with generated CV signals (it is for a modular synth so the source voltage might be an evelope, lfo etc.) not directly coupled to a pot.

 

[crutschow]

It would be rather tricky to stably convert the log control to linear.

Easier would be to just use a linear gain control element, such as an analog multiplier. You run the audio to one input and apply the control voltage to the other. That gives a very linear control of the audio amplitude.

 

[danjel]

I found that the same company has an IC (THAT 4035) that has a built in RMS level detector. Apparently I can route my CV through this to get linear control of the amp gain.