About VCF's

[gstopp at fibermux.com]

     Hi DIY'ers,
     
     I'd like to know if anybody on the list has ever built a 4-pole 
     lowpass VCF using four identical 3080 OTA integrator stages, like the 
     4-pole from the Electronotes ENS-73 series (right around issue #41).
     
     * How did it sound?
     
     * How did it handle distortion?
     
     * Are the individual offset trims on each OTA critical, or do you just
       have to trim the overall offset?
     
     Also, how about the same filter type, except using better OTA's like 
     the 13600 or 3280? Anything sound like an SSM2040?
     
     Sadly the SSM2040 is a scarce part. When I built one of those I was 
     quite surprised at the warmth of it. I've been reading the thread on 
     the "Secrets of the 2040", and I wonder if rather than trying to bias 
     a CEM3320, if a discrete design has ever been found that sounds as 
     good (except maybe an original Moog ladder).
     
     Also, I've sent an email to Analog Devices about the availability of 
     the SSM 2044/2045/2047, no response yet. Their Designer's Reference 
     databook says that these are not in normal production but are still 
     available, and I've never tried them. Are they as wonderful as the 
     2040?
     
     Thanks,
     
     - Gene
     gstopp at fibermux.com