FOur Pole Filter Trubbas!!!

[Michael Potas]

A simple fix is to change the values of the 22K resistors going to pin 5 of the 3080s to a higher value.  This will reduce the high freq response, but it means the filter will sweep lower. I was looking at this just last night on the filter I am working on!.  I found that if I use a voltage divider across the rails to control the filter cutoff, sub-sonic is no hassle (watch those drivers popping at couple of Hz...).  After I added an opamp mixing circuit so that I could use other CVs as well as control, the opamp did not output rail to rail voltage swing (I think it went to -14.4, not -15v) like the divider did, and the lower freq cutoff was compromised.  One way to get around this might be to supply power to the ca3080 through an opamp - havent tried it yet.    


Cheers,
Michael