SynthMaker

Another 24db low pass

Archive · 2005 5 old posts

From the original SynthMaker forum (2004–2014), with its members’ names and dates.

unkargherth ·

Hi all!!

I'm new here. my name is Unkargherth. Is posible you know me Before from my work in SE

Well. Wanted to start with something simpler so i ported a 24 db Low pass from music dsp source code archive to SM

It's very posible that can ve optimized and modified in some ways. If you find any, please share it here

Sorry. I has no hosting now so i post the code directly

polyin in; polyin cut; polyin q; polyout low;

float bfreq,invf,res; float pole1,pole2,pole3,pole4; float binSH,bfp,prevfp,bin,intfp;

bfreq = cut; invf = bfreq * (-1); res = q * 5; binSH = in;

// Loop starts here prevfp = bfp; bfp = (bfp * 0.418 ) + ( (res * pole4 ) * 0.582 );

intfp = ( bfp * 0.36 ) + ( prevfp * 0.64 ); bin = binSH + (-1.0 * intfp ); pole1 = ( bin * bfreq ) + (pole1 * (1 + invf ) ); // clip -1..1 pole1 = min(pole1,1.0); pole1 = max(pole1,-1.0);

pole2 = (pole1 * bfreq ) + (pole2 * (1 + invf )); pole3 = (pole2 * bfreq ) + (pole3 * (1 + invf )); pole4 = (pole3 * bfreq ) + (pole4 * (1 + invf )); // Loop (second pass) starts here prevfp = bfp; bfp = (bfp * 0.418 ) + ( (res * pole4 ) * 0.582 );

intfp = ( bfp * 0.36 ) + ( prevfp * 0.64 ); bin = binSH + (-1.0 * intfp ); pole1 = ( bin * bfreq ) + (pole1 * (1 + invf ) ); // clip -1..1 pole1 = min(pole1,1.0); pole1 = max(pole1,-1.0);

pole2 = (pole1 * bfreq ) + (pole2 * (1 + invf )); pole3 = (pole2 * bfreq ) + (pole3 * (1 + invf )); pole4 = (pole3 * bfreq ) + (pole4 * (1 + invf )); // Loop ends here

low = pole4;

...waiting your comments.

global goon ·

i've used many of your modules in SE 🙂

welcome !!!!(i moved over from SE a couple of weeks ago)

will check this code out later duud

Shifrin ·

Thanks for this code snippet unkargherth!!! Gonna check it out soon 🙂

Shif.

Tom7777 ·

Welcome and thanks this looks very cool 🙂

jorge ·

Thanks for the code unkargherth and welcome to the forum

I created a schematic using your code:

[old link] With this schematic you can listen to the effect of the filter on a sawtooth wave as the cutoff sweeps.

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