"The project proposed here is an extension board to add 15 functions to the MOTM 440 VCF and more generaly to almost all 4 poles Low Pass VCFs with a similar topology ...The idea of this extension come directly from the Oberheim Xpander/Matrix12 multi-function VCF schematic : the 4 poles of a classic low pass filter are mixed together with different coefficients to get multiple functions. The Multi-function VCF page contain math explanations and a copy of the original schematic, so i won't reproduce them here, just the list of the 16 VCFs functions as a reminder..."
click here for more info on Papareil Synth Labs. via Not Even Remotely Funny in the comments of this post.
What a coincidence, that I just yesterday wrote on KVR DSP forum a little tutorial about how to go about deriving the math to get responses like that out of a DSP model of similarly structured 4-pole (doing the math in analog, but taking 5 outputs for generality without having to mess with implementation issues).
ReplyDeletewww.kvraudio.com/forum/viewtopic.php?t=207647 if anyone cares. Might contain errors, and is written with DSP in mind, but..