Filters on older digital synths – DSP and Plugin Development Forum

Thinking about digital filter implementations on synths like the Waldorf Blofeld and Access Virus synths. Particularly implementing drive and non-linearities. A bit of DSP archeology if you like.

Given the age of those synths I’m guessing that modern(ish) techniques of solving non-linearities to closely emulate analog filters, i.e. Newton–Raphson, weren’t used. They perhaps weren’t even zero delay either?

In particular the Blofeld has a number of different filter drive types. Given the limitations of the hardware, I’m figuring the selected drive type would just be applied before filtering? (I know, some that’s kinda frowned upon nowadays). I’m guessing they’re not over-sampling either (even seems to be the case if you look at the Iridium filter response – slightly cramped near Nyquist), so the spectre of aliasing is an issue.

Anybody got any insights or thoughts on this stuff?