[sdiy] Buchla 295 weird topology

[Aaron Lanterman]

I'm checking this out:

http://rubidium.dyndns.org/~magnus/synths/companies/buchla/Buchla_2950_200.jpg

The pure lowpass and highpass sections are standard Sallen Keys with  
an unbuffered first-order passive section slapped onto the front. This  
turns it into a rather nonstandard Sallen Key. Fortunately, I found it  
in my colleague Marshall Leach's filter potpourri:

http://users.ece.gatech.edu/~mleach/ece4435/filtrpot.pdf

The 8 bandpass filters in the middle, though, are weird. To establish  
notation, consider the filter that creates output "b," the 200 Hz  
filter. If you left out C9, you could redraw it as a multiple feedback  
filter. But putting the cap in there weirds it up, turning it into  
something I haven't seen before.

Anyone recognize it? I'm hoping someone does so I can go look it up in  
some obscure textbook before sitting down and deriving the transfer  
function myself, which I can do, but would just rather not. ;)

- Aaron