SubSub page: Filtertype software
design 2017
Introduction:
Most digital filter implementations are complex (and processorhungry) but it can also be done by simply copying what you would build in hardware.
Here you see how a state variable filter can be created from a circuit to 4 lines of readable code.
Just follow the signal path and see how it is copied in the code:
This is used to dynamically sweep the digital noise generator spectrum in the Monoladder.
It even works on a 8 bit processor (ArduinoMiniPro 16MHz) with sampling clock at 32kHz. I used 8 bit data and did the calculations with 16 bit integers.
This is not so accurate but fast and on a noise generator you do not notice distortion that much.
software filter on noise, sound example from the MonoLadder
First you hear the noise, after 10 seconds the softwarefilter is on and LFO modulated, then switched from BandPass, HighPass to LowPass.
The last filter setting (45sec up) is the Band Reject with a low Q, this sounds like a phasing effect. At 1m:12s the hardware analog lowpassfilter is swept down with a sawtooth LFO modulation
(while pushing the MonoLadder softpot slider a few times).
Another application is using it on patternwaveforms (see noise software).
software filter on pattern waves, sound example from the MonoLadder
After 8 seconds you can hear that the filter starts moving and is modulated with an LFO.
More text will be added here