The Big Muff is a classic fuzz pedal it has been cloned and modified countless times over many years. If you’re into to guitar pedals you may already own one or a variant, or have seen more than a few derivatives for sale.
This is a PCB for the Big Muff. I design this in Eagle. I used the Part numbering from The Big Muff Page. With this board you should be able to build any version of the standard Big Muff. Just choose a schematic and match the part numbers to this board.
You can order boards from PCBWay.com.



Here is a sample schematic from The Big Muffin Page.

Take a look at the schematic. You’ll see that all of the parts have a number like: R14 or C1. These correspond to the parts on the PCB with the same number!
The first image below shows the all of the part numbers. The second highlights R14 and C1, these correspond to the same parts in schematic above. The third image shows the copper traces that connect the parts. Look closely at the last image, follow the red line from C1, through R9 to R14, and then to center pin of Q4. If you look closely at the schematic, you’ll see that R9, R14, C1, and Q4 are ll connected! This is is how the PCB works. There are copper traces on the board that connect all of parts matching the connections in the schematic.



All of the schematics on The Big Muff Page use the same part numbers. This means you can choose which version of the Big Muff you want to build and use the part values shown on the schematic!
My PCB adds a couple extra parts not found on the schematics. The board adds parts for power filtering, and an on board LED. The power filter, D5, R25 and C14, reduces noise. The original Big Muff did not have an LED to tell you when it was on or off, R26 D6 do that. R1 was added to prevent popping when you switch the pedal on and off with the foot switch.
These are parts I added that are not on the original schematics:
- R1 – 1M pull-down resistor to prevent switch popping
- R24 – 1K to 10K LED Resistor
- D6 – LED any
- D5 – 1N5817 Reverse polarity protection
- R25 – 100r power filtering
- C14 – 47µ to 100µ Power Filter
Here is the schematic that matches the PCB. You’ll see all of the part numbers match parts on the schematic above with the extra parts I mentioned.

Here are some pictures of the PCB that has been built. Yours will look something like this when it is completed.



Getting Started
Follow these steps.
- Choose a version of the big that you want to build from one of the schematics on The Big Muff Page. If you’re which one to choose build Version 1, it was the first, it sounds great. You can modify it later.
- Now you need parts. Read the schematic and write down all of the part numbers and values.
- You can find parts at Noise Bridge, using the parts database. Enter the part value, and the database will show you a bin number, you’ll have to find that bin!
- Or, you can order your own parts on the internet. I like these two services.
- https://stompboxparts.com
- https://www.taydaelectronics.com
- NOTE! The Volume, Sustain, and Tone pots use 9mm pots! They are all 100k. You can order this or this.
- What other parts do you need?
- Foot switch a 3PDT like this, or this.
- Two 1/4″ jacks, similar to this, or this.
- DC jack for power. Use a 2.1mm power jack like this or this.
- An enclosure. You can put the pedal into anything that it will fit! But, if you want it to look like a regular guitar pedal you can order one like this, or this.
- Soldering parts. Once you have your parts you’ll want to match the value to part number on the board. Start with the small parts first, working to the taller parts.
- Resistors
- Diodes
- Capacitors
- Transistors
- NOTE! Do not solder D6 (LED), Volume, Tone, or Sustain pots yet. Drill the box first, then places these parts, fit the PCB into the box, put the nuts on the pots, then solder. You can maneuver the LED into its opening, and solder that also. Doing this ensures that all of the parts are square to the PCB.
- Drilling the enclosure. Use the image below.
- Print the drill guide at 100%. You can cut the paper and tape it in position over the enclosure. Then drill the parked locations.
- The last step is to wire up the switch and jacks.
- Fit the jacks in the enclosure.
- Follow the wiring diagram below.
Wiring

Drilling Guide
Download the drill guide pdf.

Design Guide
Use this plan out your design. Control outlines show diameters of common knobs. The LED outline shows 3mm and 5mm outlines.
Download the design guide pdf.

Here is a gallery of the completed build. Note! Astute observers will notice that I mixed up the Tone and Volume controls on the enclosure of this first build! Follow the guide above, it is correct Volume is center bottom and Tone is upper left.


















Debugging
Follow these steps to debug.
- Check that you have power. Use your multimeter to check that you have +9v at the PCB.
- If you’ve wired everything up check that LED turns on and that you have sound when bypassed. If not check the wiring around the switch and where the four wires connect to the PCB. If the LED doesn’t light check that it is oriented correctly.
- Check the collectors of each transistor, this should be pin 3with the flat side pacing you and the pins pointing down. You should see something around 0.6 to 1.2 volts at the Base and 4.5 to 6.5 volts at the collector. If you have sound but it doesn’t sound right the voltages could the problem.
- If you don’t have any sound use the audio probe to follow audio through your circuit.
You can use the image below to help debug.

Here is a schematic. There are a couple parts added that don’t appear on schematics at the Big Muff page, these are:
- D5 1N5817 is for reverse power protection
- R25 100r and C14 47µf are for power filtering
- R24 and D6 LED are the indicator LED that shows when the effect is engaged
- R1 1M prevents popping when the pedal is switched on and off
