This one in a very nice sounding delay based on the PT2399 IC and is definitely a recommended build.
Info from Rej about his effect:
The DeProfundis Delay is a PT2399 based digital delay with aggressively 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 stock values yield a max delay time of approximately 550ms - 600ms. With a minor modifications (see below), max delay time can be extended to almost 900ms.
Tweaks & Modifications
“Love You Long Time” - Extend the max delay time
This is a very easy modification. Change the Time pot to A100K and then add a 270K resistor in parallel with Time. You can add the resistor either to the pot pads on the board, or you can use the pads marked “M1” and “M2” (see below for more info on these). Adding the 270K resistor brings the Time pot’s total resistance value down to about 75K, which is about the limit of what this circuit can handle without getting noisy and producing synth like repeats (more resistance = more delay time). If you don’t have 270K on hand, try 220K, but be aware that this will give you less max delay time. Or you could put multiple resistors in series to get close to 270K.
Even Darker Repeats
If the dark and murky tone of the stock circuit does not satisfy your black heart, try increasing the value of C7 (Mark's note: 10n cap to ground under IC2) to taste.
Video of Rej's build with modulation added. And before you ask, yes I am :o)
This version is based on Rej's notes for increasing the maximum delay time. Instead of putting a resistor in parallel with the Time pot I've used a multi-turn trimmer so you can set the maximum delay time exactly, to the point just before things starts getting a bit noisy.
Here is the modulation daughterboard for those wanting to add it to the effect. It is based on Rej's Portable LFO schematic and although it is designed for the DeProfundis, it would work equally well to add delay to other PT2399 based delay pedals such as the Deep Blue Delay.
The main modulation switch will be centre off, in one position you'll have modulated delay, in the other position you'll have modulation only.
The Shape switch will let you select a sin or square wave, and could if you prefer be swapped for a 500K linear pot which will sweep between the two waves and then give you the in between settings too.
The LED and LDR need to face each other, ideally tape them together or use heat shrink around them so you can try the circuit without it needing to be boxed first. You'll need to experiment with LED type and colour etc and LDR type to see how it works for you, or maybe use a Vactrol for an integrated unit.