BiQuad Filter

General two poles two zeros filter.

C++ code ( I made some changes to the codes and have not tested them yet, but the main algorithm should be correct )
biquad.cpp
biquad.hpp
biquadMain.cpp

Vst Plug-in (turn your volume down, be careful that the output blow up if your coefficients is not proper)
biquad.dll

Links:
Biquad Section from Professor Julius Smith