770 Type multimode VCF

[tomg]

Lasse on AH posted a link to a few Korg scans 
(thank you very much) and I was surprised to find that 
I came really close to the 770 vcf when I did the ms50/
700 hybrid...;-)  Just luck I guess....anyway I'm as busy 
as I can be getting ready to ship stuff and finishing up 
documentation but I had to stop and play with this again! 
Despite not being able to read the scan I got the 770 vcf 
working and then modified it into what you see here.

I haven't done this in a long time but hey it's Christmas
right? You guys seemed to like the Synthacon VCF.
I actually thought it was a little lame. This one works
a lot like it but I like it much *much* better. It has
a really nice sine oscillation and a not great but fairly
wide sweep considering what it is. It solves a lot of the  
problems I had last time.

Paul, The 770 has a (guess what!) 2 transistor (4 
diode) VCA I got this working too but I didn't have 
time to fix it up......too much to do ....but soon.

Schematic and untested DIY layout

http://www.xavax.com/efm/cbook/770.html

Enjoy
Tom