DIY Guitar Pedal

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Introduction: DIY Guitar Pedal

About: My name is Randy and I am a Community Manager in these here parts. In a previous life I had founded and run the Instructables Design Studio (RIP) @ Autodesk's Pier 9 Technology Center. I'm also the author of…

Making a DIY guitar fuzz pedal is a fun and easy electronics weekend project for hobbyists and guitarists alike. Making a classic fuzz pedal is much easier than you think. It just uses two transistors and a handful of other components. Aside from sharing the schematic, throughout this project I will also be going over basic tips and tricks for guitar pedal construction.

If you would like to learn more about electronics and reading schematics, check out the free Electronics Class!

Step 1: Materials

For this project you will need:

(x1) Hammond BB metal enclosure
(x2) 2N3904 transistors (or equivalent) *
(x1) 22uF capacitor
(x1) 0.1uF capacitor **
(x1) 0.01uF capacitor **
(x2) 100k resistors ***
(x1) 10K resistor ****
(x1) 5.1K resistor ***
(x1) 5K potentiometer
(x1) 100K potentiometer
(x1) DPDT heavy duty push switch
(x1) PCB
(x1) 9V battery plug
(x1) 9V battery (x2) 1/4" stereo jacks
(x2) Dial plates
(x2) Knobs
(x2) Velcro squares
(x1) 3M 30-NF Contact Cement
(x1) Drilling guides (download and print)

* Different NPN transistors create slightly different sounds. Feel free to experiment on a breadboard with the circuit before you build it.

** The 0.1uF and 0.01uF capacitor can also be swapped out for slightly different values to create different sounds. Again, experiment on a breadboard before you solder anything in place.

*** Carbon film resistor kit. Only kit necessary for all labeled parts.


Please note that some of the links on this page contain affiliate links. This does not change the price of any of the items for sale. However, I earn a small commission if you click on any of those links and buy anything. I reinvest this money into materials and tools for future projects. If you would like an alternate suggestion for a supplier of any of the parts, please let me know.

Step 2: Attach the Drilling Guides

Cut out the drilling guides and attach them with masking tape centered upon the top and side faces of the enclosure (as appropriate).

Step 3: Mark the Centers

Mark the centers of each hole using a punch (or a nail if you don't have one).

Drill pilot holes for each marking using a 1/8" drill bit.

Step 4: Drill 9/32" Holes

Widen all of the holes in the enclosure with a 9/32" drill bit (or appropriate for you potentiometers).

Step 5: Drill 3/8" Holes

Widen the holes in the side of the enclosure using a 3/8" drill bit.

Also, widen the center hole in front of the enclosure with the same drill bit.

Step 6: Drill a 1/2" Hole

Finally, widen the center DPDT switch hole in the front of the enclosure with a 1/2" drill bit. You will likely want to clamp the enclosure down to your work table (or in a vise), before you drill this hole. A 1/2" drill bit can be aggressive.

Step 7: Mark the Mounting Tabs

Insert the potentiometers into their front mounting holes backwards and upside down.

Wiggle, them back and forth, and notice you have scratched a line on the surface that corresponds to its mounting tab.

Drill a 1/8" hole along this line just to the left of the larger potentiometer mounting hole.

Step 8: Create a Stencil

Lay one of the front dial plates on a piece of painters tape.

Trace and cut out its outline.

Step 9: Place the Template

Center the front plate atop one of the potentiometer holes.

Place the tape template down around it, and stick it to the front surface of the enclosure.

Step 10: Glue Down

Apply contact cement to the center of the stencil and also the back of the front dial plate.

Wait for it to dry long enough to become tacky to the touch.

Once dry, press the dial firmly to the enclosure to glue it in place.

Step 11: Repeat

Repeat the process for the second dial.

Step 12: Build the Circuit

Build the circuit as specified in the schematic. For now, do now worry about wiring jacks, potentiometers, or anything else that might not attach directly to the circuit board.

This circuit is basically a 2-transistor gain circuit and a variation on the classic Fuzz Face guitar pedal. To learn more than you ever wanted to know about this circuit, check out R.G. Keen's Technology of the Fuzz Face article.

Step 13: Wire the Potentiometers

Solder 5" green wires to the center and right-hand pin (if the potentiometer knob is facing you) on both potentiometers.

Also solder a 5" black wire to the remaining outer pin on the 100K potentiometer.

Step 14: Mount the Potentiometers

Mount the potentiometers to the enclosure by inserting it's shaft up through the hole in the enclosure, and fastening it in placing with its mounting screw.

Step 15: Wire the Power and Jack

Connect a 5" black wire to the terminal connected to the center barrel jack.

Connect the black wire from the 9V battery clip to the terminal connected to the smaller signal tab.

Finally, connect a 5" green wire to the terminal connected to the longer signal tab.

Step 16:

Mount the jacks and potentiometers to the inside of the enclosure using their mounting nuts.

In my pedal, the input and gain pot will be on the left of the pedal, and the 100K volume pot and output jack will be on the right.

Step 17: Mount the Switch

Mount the switch to the enclosure using its mounting hardware.

Step 18: Wire the Switch

Connect one of the switch's center pin to the green wire connected to the audio / power jack.

Wire the other center pin to the identical pin on the other audio jack.

Wire together one set of outer pins.

Solder a wire between the remaining pin in-line with the output jack to the center pin on the volume potentiometer.

Finally, solder a green wire to the remaining free pin. This will later be attached to the circuit board.

Step 19: Ground Connection

Connect the black ground wire from the volume potentiometer to the terminal on the audio jack connected to the barrel.

It is important to understand what is happening here, and that it will only work with a metal enclosure. Basically, since the other jack is using the barrel connection as a switch for the ground, the entire case is electrically connected to the ground plane. Thus, the barrel jack on the other jack is also connected to ground. So, by connecting the potentiometer to it, you are effectively connecting it to ground on the circuit board (without actually attaching it to the circuit board).

Step 20: Wire the Circuit Board

Now is time to attach the components mounted to the enclosure to the circuit board.

The red wire from the 9V power clip should go to the power rail, and the black wire from the stereo jack should be attached to the ground rail.

The gain potentiometer should be attached as specified in the schematic.

Lastly, the remaining unconnected switch wire in-line with the input should be connected to the input on the circuit, and remaining wire from the volume potentiometer should be connected to the output on the circuit board.

Step 21: Velcro

Attach the circuit board to the bottom of the enclosure using self-adhesive Velcro tabs. This both holds it in place,
and prevents it from touching the lid and shorting the circuit.

Step 22: Shut the Enclosure

Plug in the battery if you have not done so already and fasten the lid onto the enclosure using its mounting screws.

Step 23: Attach the Knobs

Turn the potentiometer knobs counter clockwise until they stop turning.

Place the knobs in place with their pointers pointing at the starting position on the dial.

Fasten the knobs in place with their set screws.

Step 24: Plug In

You are now ready to plug everything in and rock out.

Did you find this useful, fun, or entertaining?
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12 People Made This Project!

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69 Comments

0
geoffreany
geoffreany

8 weeks ago

My new “peach fuzz” sounds good but I have to keep the volume a hair over minimum and the fuzz a hair under maximum to get the sound I want. Do I need to swap out my pots? Or are there other components I should change?

0
randofo
randofo

Reply 7 weeks ago

You can try replacing the 5.1K resistor with a 10K trim pot. That might help dial it in. You can also replace the capacitors at the input / output with different values. That should have some (small) effect on the sound.

0
geomy1
geomy1

2 months ago

I finally got it sounding right (I had a bad pot), but now I seem to be picking up a radio signal. I hear voices! Any suggestions?

0
randofo
randofo

Reply 2 months ago

Are you using a metal enclosure? It sounds like maybe you are having some issues with grounding. Do you have a lot of extra wire connecting the jack to the PCB or switch?

0
geomy1
geomy1

Reply 8 weeks ago

I was testing it on the bread board. Now that it is in the enclosure it sounds better.

image.jpg
0
benzwahlen
benzwahlen

1 year ago

I'm trying this circuit out on a breadboard but I'm getting a loud persistent crackling through the amp. I've checked te wiring multiple times but not luck :( Does the circuit need to be shielded or something?

0
geomy1
geomy1

Reply 2 months ago

I had the same problem. I found one of the pots was bad. Swapped it out, now it's fine.

0
Mcbernhart
Mcbernhart

4 months ago

I was able to build it but I get very low volume when the circuit is engaged. I have to turn the fuzz pot up all the way to get any sound out (which is really fuzzy and has great sustain) but the volume is significantly lower than the bypass. The volume pot adjusts the volume (within the limited range oncoming out) so I don’t think the issue is there. Any idea what could be causing it?

0
randofo
randofo

Reply 4 months ago

The 5K trim pot could be adjusted incorrectly, the transistor could be bad, or there could be incorrect wiring.

0
Mcbernhart
Mcbernhart

Reply 3 months ago

Ok, so I’m totally stumped. I still can’t get this to work at all and I can’t figure out what’s wrong. Here’s what I’ve tried so far:
1. Rebuilt the whole thing on a bread board. No luck. Still no sound when the circuit is engaged.
2. Took all of the circuitry off the bread board and just ran the input from the switch to the volume pot output and it worked perfectly. Clean sound, volume pot worked, LED lit.
3. Added the 5K pot into #2 so the input from the switch came in, went out to the 5K pot, back in from the 5K pot and out to the volume pot. This worked perfectly again: clean sound, both pots affected the volume and LED lit.
4. Added the input and output caps to #3 and it still worked.

But, once the whole circuit is on there, I get nothing. Based on the tests above, I’m pretty confident in the pots, input/output jacks, LED and 3PDT wiring.

I’ve tested all of the components individually (pots, caps, resistors and transistors) and they all test fine. The only exception is the transistors test at about 375 hFE, which, from what I understand, is a little high.

I attached pictures of my circuit board - hopefully you can see something I’ve done wrong. For reference, the top rail is power and the bottom rail is ground. The blue wires are just jumpers since the board only has 3 spots per section. As I mentioned, I did rebuild it on a bigger bread board to eliminate the jumpers and still couldn’t get it to work, so those don’t seem to be the main problem.

Any help would be great! I’m stumped...

619E989B-C113-4F7D-AEAD-334B95387C98.jpeg8301BD64-B000-4C34-995A-B3C6A9A0A41F.jpeg7F97DDB9-82C1-41F6-8FDF-B79BA96E57F0.jpeg12632E84-2FC6-4855-8D4C-30F62D089FBB.jpeg
0
Mcbernhart
Mcbernhart

Reply 3 months ago

A little more info. I built an audio probe to try to diagnose the problem and I get audio output up to the Base of Q1. Then I get nothing coming off the emitter of Q1. I’ve tried multiple resistors from 2 different manufacturers. Some, as mentioned had ~380 hFE and other had ~200. I’m really confused what is going wrong and could really use some help...

0
Mcbernhart
Mcbernhart

Reply 4 months ago

Thanks! I’m pretty sure the wiring is good, but I’ll double check. I’m worried about my transistors though. I tried testing a few new ones on my multimeter and I get 0 hFE readings on all of them. It’s my first time trying to test transistors, so I’m not sure if I’m doing something wrong or if the whole lot is bad. I tested about 10 and only 1 showed a rating other than 0 (it was 004). I’ll look at checking the 5K pot next

0
Mcbernhart
Mcbernhart

Reply 4 months ago

The pot seems to be good. It measures about 4.5V in the off position, gradually going to 0V in the full open position. I tried testing the transistors using the diode setting on my multimeter and got about 0.8V when testing both B to E and B to C. That rating seems OK but still get a 0 reading when I try to test hFE.

0
dgarciahis
dgarciahis

4 months ago

I've followed all the instructions and I've built it on a breadboard, but when I plug the pedal to my amp, it doesn't work. I have tried to figure out what's the matter, but everything seems to be ok. What should I do?

IMG-20210314-WA0043.jpeg
0
dgarciahis
dgarciahis

Reply 4 months ago

This is what I did yesterday. I don't know if I'm using the breadboard right, or if the wires aren't brazed well... I think I'm going to need to use a tester to know the cause of the problem.
P.D. I've changed the side of the Input and the output, does it matter?

16158306150208119718187590116140.jpg16158306425645957709535151316772.jpg
0
randofo
randofo

Reply 4 months ago

It is hard to say for sure, but it looks about right. Does the bypass work and can you hear audio in the amp without the fuzz effect?

0
dgarciahis
dgarciahis

Reply 4 months ago

I checked the pedal in general and I found out some issues. Now the pedal sounds, but there's a little problem. When I activate the fuzz, the volume of the amp decreases. I don't know if that is normal. I'm testing it in a bass amp, I don't know if that's relevant or not. Thanks for sharing this project!

0
debroq
debroq

Question 6 months ago on Introduction

Could you possibly build a looper guitar pedal using either an Arduino or Raspberry Pi?

0
ludoviquetor
ludoviquetor

Question 7 months ago

Hey, I've tried multiple times to make the circuit, but there seems to be no current going from the leg of the .01 cap to the 100k pot. Could my caps be busted, or not work properly?

0
randofo
randofo

Answer 6 months ago

I have no idea. It sounds like your wiring is off, but it is hard to tell what could be wrong from your description alone.