Fun With Filters

1.  http://ss30m.blogspot.com/2020/05/fun-with-filters-pt1.html
2.  http://ss30m.blogspot.com/2020/05/fun-with-filters-pt2.html
3.  http://ss30m.blogspot.com/2020/05/fun-with-filters-pt3.html
4. https://ss30m.blogspot.com/2020/05/of-envelopes-and-filters.html
5. https://ss30m.blogspot.com/2020/06/fun-with-filters-old-crow-cs-80-module.html