On Mon, Aug 27, 2007 at 11:11:39AM +0100, Gordon JC Pearce wrote: > On Mon, 2007-08-27 at 11:35 +0200, Fons Adriaensen wrote: > > > You can use atanf(), tanh(), x / sqrtf (1 + x * x), ... > > So that would hold it around unity gain, maintaining the oscillation > without going hugely offscale?
Yes. Once the oscillation is sustained the amplitude will settle at a level that corresponds to exactly unity gain. > I did briefly consider a simple "compressor" in the feedback loop with a > shortish (a few cycle's worth) time constant, the idea being for it to > work like the lightbulb or thermistor in a Wien Bridge oscillator. That would probably be much more difficult - 'a few cycles' depends on the frequency, and depending on the type of filter you have in the level detector, the whole thing may start behaving like a pulsar rather than as an oscillator (can be fun as well). But it can be done. Anyway, maintaining a constant Q (and a fixed feedback level at which oscillation will be sustained) is not obvious at higher frequencies, say above Fs/8. I remeber it was one of the more difficult aspects when I wrote the Moog Filter plugin years ago. -- FA Follie! Follie! Delirio vano รจ questo ! _______________________________________________ Linux-audio-dev mailing list [email protected] http://lists.linuxaudio.org/mailman/listinfo.cgi/linux-audio-dev
