Hey.. a new problem. My free compiler does not support any PIC18Fxx, only 12Fxxx and 16Fxxx.
http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt
Do you know if these formulas work for the biquad filters (for example bandpass)?
This would be a start.. if I don't get the ALE program. It doesn't seem to be too hard for a little pic (16F876), at least I will give it a try.

Sebastian