Non-linear ZDF filter design using the secant method

Last year I did videos demonstrating the ZDF/TPT filter design workflow for linear filters. I like the reliability and stability of linear filters, but I can also understand why one would like to add saturation to these algorithms. I think NL filters are a bit transcendental: there are so many options to add in so many ways, that it's hard to establish an objective judging system on what is good. Timestamps: 00:00 Intro 00:50 Why non-linearities? 02:14 Inserting non-linearities into the filter equation 03:30 Secant-method 04:00 ILO oversampling 04:55 Preparing the filter 05:34 Creating the solver 06:09 Building the filter equation 07:05 Inserting NL functions into the patch 09:25 Wrapping the equation into a stage 09:45 Finishing stage 1 11:46 Creating and modifying stage 2 12:50 Creating additional stages 13:18 The last f0 is the feedback 13:30 Finishing the filter 13:48 First test 14:15 We keep only 3 iterations in the solver 15:40 Creating sound test patch 16:20 Sound test 17:24 Final thoughts 18:31 Bye Our Discord server: https://discord.gg/QXQyQhRfQV We are developing Alpha Forever Modular, a modular VST plugin, and sound design tool. My latest release made using Alpha Forever sounds only: https://youtu.be/Hks0Gat8XnY Follow me at: Facebook: https://www.facebook.com/9b0music Spotify: https://open.spotify.com/artist/3LWp7Y5CCVs1HN9BG06YAw?si=X48ukA7FSVOTf9dWssMNgg Soundcloud: https://soundcloud.com/9b0 Bandcamp: https://9b0music.bandcamp.com/follow_me Discord: https://discord.gg/QXQyQhRfQV Know more about Alpha Forever Modular: https://afmodular.com