SMD 2040 filter
This VCF has been heavily influenced by Jürgen Haibles SSM 2040 filter clone.
I constructed it using mostly SMD parts, hence the name. The circuit differs from Jürgens,
in a few details. I operate the filter core with different supplies. (+15V,+5V,0V)
Thus I didn't need to lower the ground of the expo convertor.
I omitted the voltage controlled resonance, because it is easy enough to get.
If you have a spare VCA you can patch it if you need it. I'll maybe add it later,
when I do a board revision.
References:
Jürgen Haibles homepage
SMD 2040