HPF (high-pass filter) — a variable sub cut before your dirt or power amp.
It rolls off everything below the corner you set, trimming useless sub rumble that eats headroom, triggers ugly speaker flap, and smears note definition in a dense mix.
Especially useful on bass or 7- / 8-string guitars where the low B or F# can flood the front of the chain.
Corner frequency 20 Hz–200 Hz, slope 12 dB/octave.
