[sdiy] Music Easel ring mod analysis

[Aaron Lanterman]

I finally got around to doing some pencil-and-paper analysis of the  
wet/dry mixer in the balanced modular in the Music Easel (the  
circuitry driving the LEDs of VT5 and VT6):

http://rubidium.dyndns.org/~magnus/synths/companies/buchla/Buchla_2080_5_200.jpg

I found that, using the 1K at the Mod Index In input, you get a  
control law in
which an input of 0.167 volts or thereabouts gives you a 50/50 wet/dry  
mix, which is curiously small (but consistent with what I found  
working on the breadboard). If you want something more like 2.5 volts  
to give a 50/50 mix, then a 15Kish resistor is better.

Putting in a 8V pk-pk wave from an MOTM-310 and a 8V pk-pk modulating  
wave from a MOTM-320 winds up giving a "wet" ring mod waveform that's  
actually something more like 12V pk-pk.

I have some tweaks planned to "modularize" this weird thing in a  
flexible and useful way.

If I whip up a PCB for this is anyone interested?

- Aaron