2nd generation VCFs (was: Xpander VCF)

[Aaron Cram]

JH wrote:

> (...) So I guess the cap is just different
> because of the different gain of the 4th stage, thus resulting
> in the *same* pole location as the preceding 3 stages.
> I may be wrong here - somebody has to calculate it.
> 
> JH

Right.
Here's a quote from the filter section of the CEM3394 datasheet:

"The first 3 stages of the filter are unity gain transconductors while 
the last stage provides a gain of 57 (and consequently has a 
transconductance of 1/57 of the first three). This requires three equal 
capacitor values, and the fourth is 1/57 th of the other value."

This isn't the filter in question, but I assume it is of a similar 
design.  The cap values recommended are 33nF for the first 3 poles and 
560pF for the last.



-Aaron

PS.  The CEM/SSM datasheets are well-written.  I've learned alot from 
reading them (although not as much as reading the sinth-diy list! :)  
They can be found at:  http://www.synthtech.com/cem/cemdata.html