A PT2399-Based Echo Machine
In a discussion of classic delay/echo effects, the ones that most frequently get mentioned are the EchoPlex EP-3, Roland Space Echo, and the Binson Echorec. The EP3 and Space Echo are tape delays, while the Echorec is based around a magnetic disk that spins past 4 playback heads.
There have been some DIY projects in the past that have attempted to replicate the sound of the Echorec with varying amounts of success. The awesome Multiplex from 1776 Effects cops the general vibe of the Echorec, but uses only two delays instead of 4. The FV-1 chip also makes it possible to get a high level of accuracy and detail, but I'm a cheapskate and wanted to see what I could do with the old standby, PT2399.
The Echorec has a fixed delay time of approximately 300 ms, but I wanted to give a little more flexibility, so I added adjustable (but synchronized) delay times and decided to add tap tempo for good measure. Additionally, there is filtering on both the playback and feedback paths.