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// WARNING: This a "legacy example based on a deprecated library". Check filter.lib
// for more accurate examples of filter functions
declare name "lfboost";
declare version "1.0";
declare author "Grame";
declare license "BSD";
declare copyright "(c)GRAME 2006";
//------------------------------------------------------------------
// DAFX, Digital Audio Effects (Wiley ed.)
// chapter 2 : filters
// section 2.3 : Equalizers
// page 53 : second order shelving filter design
//------------------------------------------------------------------
import("stdfaust.lib");
//----------------------low frequency boost filter -------------------------------
// lfboost(F,G)
// F : frequency (in Hz)
// G : gain (in dB)
//
//--------------------------------------------------------------------------------
lfboost(F,G) = fi.TF2((1 + sqrt(2*V)*K + V*K*K) / denom,
2 * (V*K*K - 1) / denom,
(1 - sqrt(2*V)*K + V*K*K) / denom,
2 * (K*K - 1) / denom,
(1 - sqrt(2)*K + K*K) / denom)
with {
V = ba.db2linear(G);
K = tan(ma.PI*F/ma.SR);
denom = 1 + sqrt(2)*K + K*K;
};
//====================low frequency boost process ===============================
process = vgroup("lowboost", lfboost(nentry("freq [unit:Hz][style:knob]", 100, 20, 150, 1),
vslider("gain [unit:dB]", 0, -20, 20, 0.1)));
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