[sdiy] Mysterious "buffer" on Music Easel board 4

[Aaron Lanterman]

Greeting Buchlarians,

If you take a look at this particular Music Easel schematic, for board  
4:

http://rubidium.dyndns.org/~magnus/synths/companies/buchla/Buchla_2080_4_200.jpg

There's a mysterious buffer circuit on the right, just to the left of  
the CV inverter circuit. It's not mysterious in terms of what the  
circuit itself does, per se; what's a mystery to me is where it fits  
into the Easel heirarchy. I can't find any specific reference to it in  
the manual (although I might have missed something).

If you look at the big block diagrams showing how the boards fit  
together, the "buffer in" comes from S1-28, meaning it's coming from a  
pin on a voice card, and the "buffer out" goes to S3-14, which I  
believe is somewhere on the front panel. But I can't seem to puzzle  
out what part of the card this would be corresponding to, and what  
front panel jack it would be corresponding to.

Any clues?

And in case you are curious, yes, I've spent pretty much my entire  
winter break so far laying out circuit boards to mostly-clone the  
Easel, with various tap points to make it possible to almost-entirely- 
clone the Easel if someone wanted to do that. I've got an Easel LPG  
board mostly done, a board with the preamp & envelope detector and CV  
inverter about 1/2 way done, a board for the ring modulator (souped up  
with some cool ideas from Grant Richter) 95% done, and a board with  
the "timbre" nonlinearity about 75% done. Based on feedback I've  
gotten so far, it seems lots of people will be interested in these  
boards.

I've read that Mark Verbos is (was?) working on cloning the  
oscillators, so I'm going to hold off on that, and maybe skip to  
working on the sequencer and pulser once I understand them sufficiently.

I am totally obsessed with this. This can't be healthy.

One side effect is I've now gotten very fast with Eagle, which I  
simply could not stand when I started using it. I've learned to think  
in it.

- Aaron

P.S. I've rigged up my preamp/envelope detector board with a switch so  
that you can run the preamp into the ED as usual, or use the preamp  
and ED as separate devices if you want to you. The ED has an input  
impedance of 33K. Should I bother buffering the external ED input, or  
should I declare 33K high enough for rock 'n roll and not bother  
putting in another op amp?