On Sun, Aug 31, 2014 at 08:13:01PM +0100, W.Boeke wrote: > Sorry Fons, if you google "moog filter schematic" you will > see 3 stages, where a stage is a capacitor in series with 2 > transistor emitters (which have a diode V/I characteristic).
All versions I've every seen have four stages, and with three the feedback wouldn't have the right phase. If you find a schematic with three stages please post a link. Each stage is a capacitor in parallel with the series connection of two emitter impedances, and driven by a current source, the collector currents of the previous stage. > About that complicated code: I saw implentations with a lot of > code lines, and preventing oscillations originating from the > non-linear tanh functions needed a lot of care. I analysed this thing to dead around ten years ago, when I wrote the MCP plugins. There is no instability problem resulting from the non-linearity. The main problem with a straightforward digital implementation is that it becomes a bad approximation at higher frequencies, this requires some attention to get right. The easy solution is to run it at a higher sample rate. Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow) _______________________________________________ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/listinfo/linux-audio-dev
