How To Turn A Populated PCB Into A Guitar Pedal
One of my first failed DIY guitar pedal projects was when I purchased a PCB for a TubeScreamer. The board came with a detailed component list and putting it together seemed too good to be true.
However, once I’d put all the pieces in place I didn’t have a clue how to actually turn it into a pedal. There were no instructions for connecting it to a footswitch, input/output jacks and a power supply.
If you’re stuck in this same boat, I’ve created this handy little guide to walk you through how to turn your completed PCB into a fully functioning guitar effects pedal.
Which PCB Connectors Remain?
Once you’ve fully populated your guitar pedal PCB, there will be a few connectors left for you to work with. These will generally be:
- Potentiometers (Pots)
- 9v or Voltage (V)
You may also have a connector for an LED but this isn’t always the case.
There should only ever be one of each of these connectors except for Ground. There could be a couple of grounding points on your board and will help when putting everything together if you’re not comfortable jumping ground points together.
How To Connect The PCB To The Guitar Pedal Hardware
In order to connect the PCB to your hardware, you’ll need a few various lengths of colour-coded wire. The colour coding isn’t necessary, but it’s a good habit to get into as it will make it much easier to debug your circuit.
For the wire, I’d suggest single-core 22 gauge wire as it’s super easy to work with and holds its shape when trying to mould it around your enclosure.
When I first started, I used to connect all of the hardware outside the case and then try to cram it all into the enclosure when I was happy with it. While this did work, it looks incredibly messy.
Now, I add all the hardware to the enclosure first, tighten the bolts and connect the PCB last. This allows me to make the inside of my pedals look much neater and the improved cable management allows for much easier troubleshooting if something goes wrong along the way.
Once you have all of your hardware installed into the enclosure and tightened, we can begin wiring in the PCB. I’ll break this down step by step below.
How To Wire The Potentiometers
Potentiometers, also known as variable resistors, have three connection points.
Connection point 1 is the input, connection 2 is the variable resistance selector and point 3 is the ground.
Your board will have connectors for each of the potentiometers required for the circuit and these will be clearly labelled and numbered.
Connecting these potentiometers to your board is a case of matching the numbers on the circuit to the lugs or connectors of the pot.
How To Wire The 3PDT Footswitch
Wiring the footswitch of a pedal may seem really complicated and it will take you a little time to get your head around. However, here is a simple guide for you to follow.
Standard 3PDT switches have 9 connectors on them and we’ll be using all of them for our pedals.
Follow these simple steps to wire a 3PDT footswitch for your guitar effects pedal:
- Connect points 1 and 2 with a jumper wire.
- Connect points 3 and 7 with a jumper wire.
- Connect point 4 to the input of your board.
- Connect point 5 to ground.
- Connect point 6 to the tip of the out jack.
- Connect point 7 to the top of the in jack.
- Connect point 8 to an LED and then to the voltage input.
- Connect point 9 to the output of your board.
Some boards will actually have a connector for an LED and if this is the case, point 8 of your switch will go through to an LED and then to that point instead of the voltage input.
There are lots of different wiring diagrams available but I’ve found this version to work the best for me.
If you find it tough to deal with the connector jumper wires, you can purchase footswitch daughter boards that handle all of this for you. When working with a daughterboard, you solder the switch into the 9 holes and then use the labelled outputs to connect it to your hardware. This is much easier to work with but adds a little extra cost to your projects. If you can afford them, I’d highly recommend picking up a pack from eBay.
How To Wire The Input & Output Jacks
The wiring of your jacks will slightly differ depending on whether or not you’re wanting to use a battery as well as mains or just mains power.
If you want to just use a power jack and source your power from a 9volt power supply, you can use mono ¼ inch jack inputs. However, if you’re also wanting to use a battery, you’ll need to use a stereo ¼ inch jack for the input of the pedal. This extra connection will help us connect to the battery power when a jack is inserted into the pedal.
Mono inputs have two connection points. The Tip and the Sleeve. The Tip is used for your input/output signal and is also live whereas the Sleeve is your grounding point.
Stereo inputs have three connection points. The Top, the Sleave and the Ring. The addition of the Ring connector allows us to add an auxiliary feature which in some cases could be splitting your signal into left and right channels but with our guitar pedals, it connects us to the battery power. We’ll use the Ring to connect the input to the negative side of the battery (the smaller battery terminal).
How To Wire The Power Jack & Battery Connector
As previously mentioned, you can choose to power your pedal with mains power through an external power supply or with a 9v battery. However, there is also another thing you have to take into account and that is the polarity of your circuit. Most pedals will be centre negative but some old germanium circuits like a Fuzz Face will be centre positive.
If you choose to go down the mains power only route, then you can stick to mono jacks for both your input and output. However, if you’d like to use both battery and mains, you’ll need a stereo jack for your input to help connect your battery to the circuit.
DC inputs have 3 connectors, just like a potentiometer.
Connector 1, which is also the largest lug, is your ground connection. Connector 2 is the power from your battery (if you’re using one) and connector 3 is to supply power to your PCB.
If you’re wanting to use a battery as well as mains power, connect the red wire from the battery snap to connector 2 and the black wire to the ground (connector 1).
If your pedal requires centre positive power, the wiring of the jack input will be a little different. Connector 1 becomes your power to the board and connector 3 goes to ground. The red wire of your battery will need to go to connector 1 and the black wire will run to connector 2.
With all of this in place, you should be ready to plug it in and start playing.
If there is any hardware I’ve missed that you’re having trouble with or would like more information on, please let me know and I’ll update my guides wherever possible.