The TweakTone Delay is a PT2399-based digital delay with highly filtered repeats and the possibility of very long delay times (and minimal delay line noise). There is also a tone control trimmer to adjust the high-pass cutoff frequency on the repeats.
The circuit was originally based on the Mad Professor Deep Blue Delay, but has been heavily modified.
The stock values yield a max delay time of approximately 550ms – 600ms. With a minor modification (see file pack), max delay time can be extended to almost 900ms. Granted, at these longer delay times, the filtering is very aggressive and murky.
Download the TweakTone Delay file pack.
Contains: Schematic image, PCB layout image, legacy PCB build guide document with notes, and Eagle CAD files.