This is Craig Anderton’s “Stage Center Reverb”, which first appeared in the September 1976 Guitar Player Magazine. We have added some minor improvements provided by Mark Price. This project is a spring reverb effect, which means that in addition to the stompbox-sized box with the circuit and connections for guitar, amplifier and power, you will also need a spring reverb tank (as found in most amplifiers that have reverb) and a set if two shielded cables with “RCA” style jacks. We tested this circuit with several different spring reverb tanks and found that these are the identifiers of the reverb spring tanks that work well with this circuit:

Description from General Guitar Gadgets.