[sdiy] CEM3372 passband gain trick?

[David G Dixon]

> Looking over the CEM3372 VCF datasheet, this line caught my eye:
> 
> "A unique feature of the 24db/octave filter is that, unlike 
> others of this type, the passband gain reminds constant as 
> the amount of resonance is varied, this eliminating the 
> annoying drop in volume at higher resonance settings."
> 
> Any ideas how the CEM3372 pulls that off?

It might do it the same way my 2164 4P LPF does it: with separate
voltage-controlled resonance gain cells for each stage, the first three with
gains that vary from 1 to 1.42, and the fourth with a gain that varies from
0 to 1.42, and which feeds back to the first stage.

> P.S. What does "VCF Uses Open Loop Design for Enhanced Sound 
> Richness" mean?

No idea.