[LAD] Software sound

Fons Adriaensen fons at linuxaudio.org
Sun Aug 31 20:26:18 UTC 2014

On Sun, Aug 31, 2014 at 09:00:08PM +0100, gordonjcp at gjcp.net wrote:
> Correct.  Even the "18dB/octave" Roland TB303 ladder filter has four stages.
> Why isn't it 24dB/octave?  Because they're more honest about the real-world
> performance than Moog :-D

Or they may be some IP related issues.
> Once you go hanging weirdass source and load impedances off your ladder the
> response can vary wildly.  Tim Stinchcombe has an incredible analysis which
> shows all sorts of odd bumps and peaks in what you'd typically expect to be
> flat passband.

Yes. In a first approximation the filter isn't to difficult - each stage
is in fact nicely isolated from the following once (since emitter current
will determine collector current, and collector voltage won't affect that
very much since the bases are almost grounded for AC.

> Fons - ever considered turning your analytical skill to the MS20 and Steiner
> Synthacon diode-chain Sallen-Key filter?

If you can provide a schematic I may be tempted...



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