Pigtronix Echolution-2 Deluxe - Manual (Page 10)

Filter
SHORT PRESS cycles between:
LP (Low Pass Filter)
TAPE (Analog Tape emulator)
COMB (All Pass Comb Filter)
SWEEP (Resonant Sweep)
LP + SWEEP
TAPE + SWEEP
COMB + SWEEP
NO FILTER
When SWEEP is active, the filters are swept at a rate
determined by the LFO SPEED knob. Try using the LFO
SYNC to TAP function for some incredible synchronized
delay / filter effects.
LONG PRESS turns on the CRUSH filter. This is a proprietary
bitcrusher/destruction filter that smashes the audio in the
delay line according to how loud the input signal is.