[sdiy] CEM3372 passband gain trick?

[Lanterman, Aaron]

On Aug 11, 2012, at 10:29 PM, Lanterman, Aaron wrote:

> "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?

I think I may have just answered my own question... if you look at the datatsheet (easily found via google), it looks like the resonance feedback path goes in to the negative input of the resonance variable gain cell, and the input to the 4-pole cascade also goes to the *positive* input of the resonance variable gain cell. So it looks like when you turn up the Q, it basically also turns up the input to the filter, so there's no super-sophisticated magic going on, at least I think...

- Aaron