Apocatastasis (feedback Return for Cheap Digital Delays)

Most expensive analog delay pedals have a feedback knob that lets you drive the output of the delay effect back into the input. My Ibanez DL5 Digital Delay did not have this feature, so I decided to make one and make it cheap. :-)

photo's by Laura Stretz

Step 1: Parts List

Chassis and knob:
Wanted to use an altoids tin, but my phone jacks wouldn't fit and i didn't want to switch to minis. So I found this Project Enclosure (3x2x1") at my local radioshack for $2.30
absolutely had to use the most obnoxious chickenhead knob I had. Got from mouser for $2.40

Components:
1 x .05uf film cap
1 x 10k resistor
1 x 1k resistor
1 x 10k 12mm log pot
wire (I used 22AWG solid core because it's what I had, use what you want here)
total cost per mouser: $2.47

Jacks, Cable, & Plugs:
I had a cheapo instrument cable that had a short in it somewhere, so I cu the ends off and used the cable for this project. I rang out each piece to make sure it didn't contain the short.
Jacks are Radioshack 1/4" Mono Panel-Mount Audio Jack (2-Pack) $3.99
Plugs are Radioshack Standard Phone Plug (2-pack) $3.99

Grand total cost: $15.10 (The jacks were a little cheaper in the store and everything is cheaper if you get it somewhere that's not RadioShack. It's concievable to get this down to about half the cost without too much effort)

Step 2: Schematic

The schematic is really simple though it was a little challenging to get the idea working at first. Basically you are splitting the output and building a passive mixer for the input. I started with a 10k resistor on the instrument input but there was too much of the output mixing in, so i switched it to 1k and that solved the issue. I also found that when the feedback was way off in the weeds (pot turned all the way up) there was a really high pitch every delay and that sucked. putting in the cap solved the issue and after using it for a few practice sessions now i'm happy with it.

Step 3: Assembly

i didn't bother making a PCB for this because there were so few components. Everything is wired point to point matching the schematic.
Tip:
When wiring the mono jack on the one side, the sleeve and ring are reversed from the first side, not parallel. If you touch the jack and it sends a humming sound through the line your shield and tip are the wrong way round.

More tips:
Using a straight edge to draw an X on a side corner to corner is a good way to find the center of plane for drilling.
Hot glue on the inside stops the cables from pulling out of the box.
You could try to put 4 jacks in the box instead of 2 cables, though then you'd have to buy patch cables to use it, and a bigger box, and you might wire it wrong if you're in a hurry.

Step 4: Enjoy the Sweet Sweet Feedback That Goes on Forever

Here are some samples, first one is just the delay pedal without my feedback box
just the pedal

Next is my feedback box at a reasonable feedback level. Notice the much extended repeats of the delay
some effect
a little more

Here's the fun part, the feedback going off in the weeds. Yeah, it pretty much just does this forever.
there ya go
way out there

Maker's notes:
varying the repeats and the delay time while a lot of the output is fed back in causes some interesting things to happen.
this may work on other pedals like distortions or flange/phasers, though I haven't tried that yet as I have yet to build a flanger or phaser.