Judging by KVR forum timestamps, both Vadim's "the Art of VA Filter Design" and my thread about how to do non-linearities cheap (if you'd rather not use Newton; I think the requirement to iterate non-linearities is what kept most people from using these methods earlier) date back to 2012. The ZDF/TPT/trapezoidal method was probably discussed here before that, though I can't remember exact dates or threads to lookup. In any case, by 2014 this stuff was "old news" for those "in the know."soundmodel wrote: ↑Fri Mar 22, 2024 1:59 pm I wonder what these filters prior to 2014 used as references? Or are they possibly individual "hacks" regarding e.g. stabilization of DF-II?
Before that some well known methods would be using Euler with extra unit delays (and sometimes compensation filters) to make the feedback loop implementable if you wanted (mostly) sensible time-varying behaviour .. or various state-space designs, etc... and then you'd typically use direct forms (or perhaps lattice-ladders) when you'd want predictable frequency response.