Qfilter

The Qfilter is an envelope-controlled filter from Formula B with a mode selector for high-pass, band-pass and low-pass response and a two-position switch for a low- or high-frequency range.

A Peak control sets the cutoff frequency and a Gain control sets how much signal triggers the envelope, while a second footswitch flips the sweep direction between a low-to-high and a high-to-low auto-wah. It covers funky quacks, vowel-like sweeps and synth-style filter effects. Hand-built in Todi, Italy by Marco Bovelli.