Zeitgeist is a design for a delay effect/sound source based around heavy abuse of a PT2399 karaoke delay chip devised by Rob Hordijk.
Eagle .sch and .brd provided, along with gerbers ready to go. BOM included Art Included Tayda Enclosure Drill Template: https://drill.taydakits.com/box-designs/new?public_key=bjFJdjJ0OW5hZGFLbC9yd1lEM01qQT09Cg==
This fits in a 1590BB2 enclosure. The jack and switch PCBs aren't strictly necessary if you don't mind doing some more wiring.