Dan;
2010/3/2 Daniel Trueman
i have no idea if this will help, but i've been meaning to bring the old gQ filter stuff to ChucK for sometime. gQ is a really nice filter:
That's a good idea in any case. More filters would be better. I'd still like a a state-variable filter with three outputs. Such filters are spectacularly useful in modular synthesis yet often under-appreciated in the digital context.
http://www.music.princeton.edu/~dan/gQpage/gQ.html
it might be more stable. maybe not. it usually sounds real nice. in any case, here it is, and it seems to work ok. probably should make a class out of it...
Sounds great! I'd say, BTW, that unless this is implemented as a new object with three outputs it could also be made a part of the old plan to extend LPF, BPF and HPF to be able to switch to different topographies. I have to say though that the plain "convenience" filters like BPF are -from memory- 2nd order Butterworth filters. That's hardly a exotic type of filter. At the very least they should be stable for static settings with a reasonable Q. For what I understand of DSP there are two ways to get into the current situation; you can make a typo or reasoning error in the function that sets the coefficients or there can be instabilities induced by rounding due to finite word-length. These can be checked for, though of course at some computational price. These, IMHO, need to be fixed, as something is plainly buggy there. How much time would this take from somebody who is fluent in C/C++ (needed to evaluate the rounding possibility) and not too scared of the Z-plane stuff? I'd look into it myself but I'd be out of my league in both fields. Yours, Kas.