[sdiy] Music Easel ring mod analysis

[Grant Richter]

With all due respect to yourself and Mr. Buchla.

A few days fooling on the breadboard and some fast Audiohm  
optoisolators and you could come up with a FAR superior circuit.

Mr. Buchla is a practical engineer, he takes a design to the point  
where it work goods enough and moves on.

Additional work expended on the circuit can only result in improvements.

In this case even using a VTL5C1 would probably extend the frequency  
range.

On Nov 18, 2008, at 1:55 AM, Aaron Lanterman wrote:

> 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
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