Resonator

White key 8. A tuned comb feedback loop that rings at a note you set. While on, it taps the signal after the phaser and feeds it back in after the freezer, so the ringing goes through the inserts in between on every trip.

Knob	Page 1	Page 2
1	Pitch: 22 Hz to 880 Hz (default 110 Hz)	—
2	Feedback: up to 98% (default 0, off)	Stereo: the right channel up to 12 semitones higher (default off)
3	Tone: the loop’s lowpass, 1 kHz to 15 kHz (default 6.6 kHz)	Band: what goes into the ringing loop
4	Env mod: the feedback rises with the input’s level, so loud notes ring longer (default off; the SP-404MK2’s ENV MOD)	Level of what it rings

• With other effects: on its own it’s a comb on the incoming signal. With the inserts inside the loop on, the ringing goes through them on every trip: through the shifter it spirals, through the crusher it turns grainy, the filter shapes it the way a filter in a dub delay’s feedback does, and the phaser sweeps through it. With the freezer on, it rings the repeats; with the slicer on, the ringing is chopped into bursts.
• Feedback inside the loop: an insert in the loop with feedback or resonance of its own (the phaser, the flanger, the filter’s resonance) raises the loop’s gain. The phaser’s peaks between its notches are about +4 dB at its default feedback and +16 dB at 85%, so with it on, the ringing runs away (and the soft clipper holds it) already at a low resonator feedback. Nothing evens that out by itself: for less, turn the inserts’ feedback or the resonator’s down.
• The loop holds a soft clipper, a lowpass (Tone) and a 50 Hz highpass, so it saturates rather than runs away, whatever is inside it. It turns the input down as the feedback goes up, by half at the most.
• LEDs: the key is lime; the knobs go orange to light blue.