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 One pole filter, LP and HPType : Simple 1 pole LP and HP filterReferences : Posted by scoofy[AT]inf[DOT]elte[DOT]huNotes : Slope: 6dB/Oct Reference: www.dspguide.comCode : Process loop (lowpass): out = a0*in - b1*tmp; tmp = out; Simple HP version: subtract lowpass output from the input (has strange behaviour towards nyquist): out = a0*in - b1*tmp; tmp = out; hp = in-out; Coefficient calculation: x = exp(-2.0*pi*freq/samplerate); a0 = 1.0-x; b1 = -x;

 CommentsAdded on : 05/01/07 by dj_rejo[ AT ]hotmail[ DOT ]comComment : Why don't you just say: Process loop (lowpass): out = a0*in + b1*tmp; tmp = out; Simple HP version: subtract lowpass output from the input (has strange behaviour towards nyquist): out = a0*in + b1*tmp; tmp = out; hp = in-out; Coefficient calculation: x = exp(-2.0*pi*freq/samplerate); a0 = 1.0-x; b1 = x;Added on : 05/01/07 by scoofy[ AT ]inf[ DOT ]elte[ DOT ]huComment : There's a tradition among digital filter designers that the pole coefficients have a negative sign. Of course the other one is also valid, and sometimes these notations are mixed up. If you're worried about the extra negation operation, then you could say b1 = -x; a0 = 1.0+b1; so that there's no additional operation overhead. -- peter schoffhauzerAdded on : 06/01/07 by nobody[ AT ]nowhere[ DOT ]comComment : Of course, you don't need tmp. Process loop (lowpass): out = a0*in + b1*out; Added on : 16/02/07 by scoofy[ AT ]inf[ DOT ]elte[ DOT ]huComment : Indeed.              Added on : 18/06/09 by bob[ AT ]yahoob[ DOT ]comComment : Or... out += a0 * (in - out); :)               Added on : 12/10/15 by djdelaflav[ AT ]gmail[ DOT ]comComment : can you please send me a few pictures to show me how you hooked up the mixer on the back...

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