This is a PCB for the Big Muff. I design this in Eagle. I used the Part numbering from The Big Muff Page here. 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.
The board adds a power filter section and on board LED. This makes for an easy great looking and reliable build.
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
BOM
Choose a version of the Big Muff you want to build from the schematics here:
http://www.bigmuffpage.com/Big_Muff_Pi_versions_schematics_part1.html
Match the part numbers on the schematic to the numbers printed on the PCB.
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
