The Sentinel – Echo Drone
A pitch modulator, delay, sewer pipe reverb and drone verb.
It has four controls…two are for modulation and two are for the delay.
Speed – The speed of modulation
Depth – The depth of the modulation effect
Drone – The feedback of the delay
Width – The delay time of the circuit
More information and schematic can be found here:
https://www.diystompboxes.com/smfforum/index.php?topic=102861.320