Follows are detailed instructions on how I made my own digital delay pedal. I must admit that I used a laser cutter as an integral part of the process, but I feel most of the tasks that I am using it for can be performed with many more modest tools. My focus of the Instructable is not so much in the assembly of the circuit, but the assembly of the case, as this is where the real crux of the problem lies. Cramming a lot of things into a little enclosure is not particularly easy. Yet, it's my hope that these instructions will help in some way to simplify the process.
Long Delay without Feedback:
Long Delay with Feedback:
Step 1: Go get stuff
(x1) "BB"- sized Steel Enclosure
(x1) PT2399 Echo Processor
(x1) TL072 low noise op amp
(x3) 100K potentiometers
(x1) 50K potentiometer
(x1) 5K potentiometer
(x1) DPDT stomp switch
(x1) SPST toggle switch (SPDT okay)
(x1) Power jack (with cut-off)
(x2) 1/4" mono jacks
(x1) sheet 1/16" santoprene rubber (McMaster-Carr 86215K22)
(x1) sheet 1/8" cork
(x1) 4.7 uF
(x6) 1 uF
(x3) 0.1 uF
(x2) 0.082 uF
(x3) 0.0027 uF
(x2) 0.01 uF
(x1) 100 pF
(x1) 5 pF
Step 2: The Schematic
The things that I have changed are a few mildly significant resistor and capacitor values. The biggest difference is that I have removed the "long delay" distortion pot. This potentiometer is basically forcing the chip to under-sample the input to create a longer delay and, in my opinion, doesn't sound very good. If you like under-sampled, long-delayed, audio, by all means throw in a large (1M) potentiometer in series with the delay pot. As you may have also inferred from this, the longer the delay, the less clear the output signal; so be warned that even the "short delay" starts to degrade when cranked up all the way.
For redundancy sake, I have redrawn the schematic. I have put three image notes on my schematic to indicate parts of the circuit that have changed. The schematic drawn by Casper Electronics is much more clear and I recommend you mainly go by that one.
Step 3: Breadboard the Circuit
There are a couple of reasons:
1) To make sure you get it right in the first place. There is nothing worse than soldering a circuit permanently in place to find out it doesn't work.
2) This method allows for experimentation. For instance, should you not like how it sounds, you can easily swap out parts until you do.
3) You can easily expand upon the circuit.
4) It is also quick to do and if you discover that you don't like the circuit at all, you didn't just waste a lot of time soldering.
5) It gives you a reference to go by when you finally do decide to permanently solder it together.
Step 4: Solder the Circuit
If you have enough parts to do so, it is recommended that you leave the breadboard intact as a point of reference. It is wise to only disassemble the breadboard after you are absolutely sure the soldered circuit works.
Step 5: Make Rubber Brackets
These two pieces will go between the potentiometers and the case, and the switches and the case. They will function to prevent the body of the potentiometers and switches from rotating.
Step 6: Stencil the Front
If you don't have a laser cutter, print the file onto adhesive paper, stick it to your enclosure and cut it out with an Exacto knife
Step 7: Paint
Tip: To keep your brush from drying out between coats, you can leave it submerged completely in the enamel.
Step 8: Drill
Using a 1/2" drill bit, align the bit to the center of the marking for the foot switch button and then drill.
Replace the 1/2" bit with a 9/32" drill bit and repeat the process of aligning and drilling to make 5 holes for the potentiometers.
Step 9: Peel
Step 10: Drill Some More
To figure out where to drill these holes I temporarily installed some potentiometers, then using tape stencils and the parts to be installed, I figured out the exact position of the hole on the inside of the case. Once I had this in place, I lined up an identical stencil on the outside of the case. The theory here is that the hole on the inside matches the hole on the outside, such that when you drill through, your part should fit in precisely where it needs to be.
I found what works best in this case is if the 1/4" audio jacks are situated between and "above" (when looking down inside the case) the two rows of potentiometers (and also far enough from the edge to account for the lip of the lid). The switch and power jack position are less critical, but should also be situated "above" the potentiometer.
Once all of your tape is in decidedly place, drill your holes.
Step 11: Etch Again
Anyhow, simply place a piece of paint over the hole and use a pencil or blade to poke through the tape and expose the hole. Next, place the box in a drill press vice. Lower the bed of your laser cutter about one foot and then place the whole shebang inside. The easiest way to do this is turn off the x/y axis lock, turn on the red dot pointer, move the laser head to where you feel the zero-point should be and then reset the laser's home. Then, with a little bit of trial and error and few pieces of tape, you should be able to get the right alignment.
Etch using the following settings:
If you don't have a laser cutter, make some stencils as before and affix them appropriately to the case.
When you are done, repeat the process of painting, peeling and picking away excess paint.
Step 12: Cork Lining
The attached file can be used in a laser cutter and produces a shape that accounts for the lid's inner lip and screw holes.
I have attached the cork to the lid with some spray glue. In retrospect, I should have lined the edges with blue tape before spraying as I needed to wash the spray glue off afterward (which was a pain in the neck).
Step 13: Pots and Switches
Don't forget to align the potentiometers to their appropriate labels.
100K - Dry Volume
100K - Wet Volume
100K - Repeat
50K - Delay
5K - Feedback
Step 14: Wire the Front Panel
I recommend using different color wire for each pin not connected to ground. For this assortment of wires, I used the wiring harness from a broken computer power supply. This gave me many different colored wires to chose from.
Step 15: Wire the Power
Connect another black wire between the unused pin and ground on the circuit board.
Also, connect a red wire from the red power pin to the center pin of your SPST power switch. Connect one last red wire to the terminal that makes connection to the center pin when the switch is toggled to the "On" position.
Step 16: Connect the Front Panel
Step 17: Wire Everything Else
If your case is conductive, you only need to connect one pin from the jacks to ground. The other pin will make a connection through the case.
That said, make sure you connect the input and output jacks appropriately. In case you don't know what appropriately is, the input and output pins should be connected respectively to the center pins on the DPDT switch. One outside pair of pins should be connected to the circuit board (paying careful attention to "In" and "Out"). The other set of pins should be simply tied together for true bypass.
Step 18: Finishing Touches
Use a wrench without serrations to tighten the nuts and tightly fasten the potentiometers, switches and jacks onto the switch.
Plug in a 9V battery.
Put everything inside the case, put the lid on, make sure you can insert plugs into both jacks unimpeded and then screw the case shut.
If you haven't done so already, put on the potentiometer knobs and tighten their set-screw.
Lastly, you may want to consider putting some self-adhering rubber feet on the bottom.
Step 19: Plug and Play
If rocking out is not working, DON'T PANIC!
Open the case back up and debug the problem.
Here are some tips for debugging:
1) Is it turned on? Well... turn it on.
2) Does the battery have charge?
3) Are there any bridged connections on the PCB?
4) Do all of the connections match the schematic?
5) Have you wired the switches correctly?
6) Have you routed the cable properly from IN to OUT?
7) Is the volume turned up on your guitar and amp?
8) Is your amp even on?
9) How about the volume on the pedal?
10) If its on but not delayed, have you tried stepping on the foot switch?