A general-purpose 2nd-order (biquad) filter. A single Type selector switches between eight standard responses — lowpass, highpass, bandpass, notch, peaking, allpass, low shelf and high shelf — so one block covers most everyday equalisation and filtering jobs. Set the corner or centre Frequency and the Q (resonance / bandwidth) for every type; the Gain dB control shapes the boost or cut of the peaking and shelving types, and a separate post-filter Output gain trim scales the level after filtering. The coefficients come from the public-domain RBJ Audio EQ Cookbook designs and are recomputed the instant a parameter or the sample rate changes, so the response always tracks the incoming signal's sample rate.
Each channel runs a Direct Form II Transposed biquad, advancing exactly one sample-frame per tick to stay inside WaveWarp's sample-per-sample engine. Changing the Type, Frequency, Q or Gain re-derives the five coefficients from the RBJ cookbook formulas; the Output gain is then applied as a linear scale on the filter output.