expression pedal for the neutron? (Mutron-III clone by R.G.)

[psst]

The idea is to be able to add a expression pedal connector to my home made neutron.
When you connect the expresion pedal to the neutron it would disconnect the envelope detector and the expression pedal's pot would be the one that controls the sound. Quite simple to do.
BUT, the problem is that there are two variable resistances involved, so the only solution I see is attaching two cables connected to a stereo (two inner pots) expression pedal.
Any suggestions for a solution that involves only one pot?

[R.G.]

The only thing you have to do is replace the single voltage that is derived from the input signal loudness with a voltage from the expression pot. No dual pots needed.

[psst]

Thanks, RG.

[psst]

Trying to measures voltages, I found voltage in pin 7 of opamp 1 too low to measure, so I thought of putting the voltage required to drive the LEDs in the pin 1 of opamp 3, where I could measure it perfectly (sweeping goes from 3V to 5.5V there).
Calculating with Ohm's law I found a little circuit that gave me 3 and 5.5V depending on the possition of the expression pedal (1k-24.2k).
I should have noticed that once connected to the circuit, circunstances change, so although without connecting my calculations were right, not after that.
What do you think are the good values for the two resistances to build the little circuit with the 24.2k pot?
And do you think it's better doing it on pin7, opamp 1 or on pin 1, opamp 3?

Thanks!!

[psst]

Mmm...
Now that I think about it an easy solution would be measuring voltage in both sides of the envelope detector LEDs and applying voltage there, that would do calculations with Ohm's law very easy...
I'll try that.

a.