|Cascaded resonant lp/hp filter|
Type : lp+hp
References : Posted by tobybear[AT]web[DOT]de
// Cascaded resonant lowpass/hipass combi-filter
// The original source for this filter is from Paul Kellet from
// the archive. This is a cascaded version in Delphi where the
// output of the lowpass is fed into the highpass filter.
// Cutoff frequencies are in the range of 0<=x<1 which maps to
// 0..nyquist frequency
// input variables are:
// cut_lp: cutoff frequency of the lowpass (0..1)
// cut_hp: cutoff frequency of the hipass (0..1)
// res_lp: resonance of the lowpass (0..1)
// res_hp: resonance of the hipass (0..1)
var n1,n2,n3,n4:single; // filter delay, init these with 0!
fb_lp,fb_hp:single; // storage for calculated feedback
const p4=1.0e-24; // Pentium 4 denormal problem elimination
Added on : 13/07/03 by office[ AT ]hermannseib[ DOT ]com
I guess the last line should read
Added on : 26/12/03 by couriervst[ AT ]hotmail[ DOT ]com
excuse me which type is? 6db/oct or 12 or what?
Added on : 02/02/04 by christianalthaus[ AT ]gmx[ DOT ]de
result := n2-n4
Added on : 25/01/11 by voss[ AT ]alinear[ DOT ]net
WOW this is old but handy. Anyway what to do about the divide-by-zero caused by the feedback calc if the cutoff is set to 1.0?
Also, should the feedback for the hpf be:
Added on : 17/03/17 by Gsound[ AT ]gmail[ DOT ]com
Nobody can see ?
There is two lowpass filters in series, no differences between them.
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