[sdiy] Calling all Buchla lowpass gate fans

[Aaron Lanterman]

OK, I can switch between three modes now - replacing the 51 ohm  
resistor with a 1 megaohm resistor, which is what it was supposed to  
be, helped quite a bit. ;)

Check this out:

http://rubidium.dyndns.org/~magnus/synths/companies/buchla/Buchla_2080_10_200.jpg

OK, there's three CMOS switches there. One I'll call "top," which  
switches a 0.0047 sallen-key feedback cap in and out, and two I'll  
call "bottom," which are driven with the same control, that switches  
in and out a 15K to ground near the FET buffer and a 10K to ground in  
the feedback loop of the input buffer.

Testing the voltages at the control inputs on my CMOS switch, I see my  
three modes either:

1) Have all switches OFF.
2) Have the top switch ON an the bottom two OFF.
3) Have the top switch OFF and the bottom two ON.

All three modes have a different sound, but I'm not entirely sure what  
I should be listening for.

Question - is this what a Buchla LPG is supposed to do?

There doesn't seem to be a mode to have them all switched ON.

- Aaron