Guitar Pedal Jack and Footswitch Wiring
There are various options for how the input and output jacks, power jack and/or battery, and footswitch can be wired up in a guitar pedal. Below are wiring diagrams for some of the most common jack and footswitch wiring configurations used in modern builds. These are all wired for true bypass, with the effect input grounded when disengaged.
Figure 1 is one of the simplest ways of wiring a pedal. It uses a power supply only (no battery) and has no indicator light. A DPDT footswitch is all that is needed for true bypass switching, however a 3PDT can also be used. If using a 3PDT switch, one of the poles (one column of lugs) can be ignored.
Figure 2 adds a little complexity to Figure 1 due to the inclusion of an LED indicator. A 3PDT footswitch is necessary for turning the LED on/off when the pedal is engaged/disengaged. “CLR” is the current-limiting resistor, which controls the current through the LED and thus its brightness. Our prewired LEDs have current-limiting resistors integrated into them, so a resistor does not need to be wired in. In that case, the red LED wire can connect directly to 9V.
Figure 3 adds a battery clip to Figure 2 and replaces the unswitched barrel jack with a switched barrel jack, allowing the pedal to be powered by a 9V battery or a power supply. The mono input jack has been replaced with a stereo jack, and the battery clip’s ground connection is made to the ring terminal of the input jack. This method of battery wiring will disconnect battery power when the input jack is disconnected.
Figure 4 shows the simplest way of wiring a “positive ground” pedal. “Positive ground” pedals operate with the positive connection of the power supply connected to ground. In schematics and wiring diagrams, the power rails are usually referred to as GND and -9V. Fuzz pedals that use PNP transistors (which includes most vintage germanium fuzz pedals) are commonly intended to be positive ground pedals. These can be powered by the same 9V batteries and power supplies as other pedals, however issues arise if the user wants to daisy-chain power when using a positive ground pedal. For more info, see our PNP "Positive Ground" Pedal Considerations tech article.
Wiring a positive ground pedal as battery-only eliminates the potential for the end-user to run into problems by powering the pedal incorrectly. It is also how most vintage fuzz pedals were wired, so it is the most “vintage-correct” method for many builds. Many users also believe those same fuzz pedals sound slightly different when they are not powered by a 9V battery (perhaps due to the internal impedance of the 9V battery). Most fuzz pedals draw very little current. With no LED, 9V batteries can last a very long time in this type of circuit. The input jack should be disconnected when the pedal is not in use to disconnect battery power and preserve battery life.
Figure 5 shows a modification of the Figure 4 wiring. The wiring has been modified to include a “battery disconnect” switch. Figure 4 is wired such that battery power is disconnected when the input jack is removed. Some users prefer to have a physical switch on the pedal that can be used to disconnect the battery. This is particularly useful when the pedal has semi-permanent input and output connections as part of a pedalboard layout. Disconnecting the input jack will still disconnect battery power, but the user also has the option of doing so with a switch.
Figure 6 shows the same wiring as Figure 4, only this time it is for a standard negative ground pedal. Negative ground pedals do not have the same daisy-chaining issues as positive ground pedals, so you tend to see barrel jacks on negative ground pedals more commonly. However, battery-only is still often how early negative ground pedals were wired, and modern builds of those circuits often opt for battery power only. Like the positive ground builds, a 9V battery will last a very long time in most negative ground fuzz circuits.
Figure 7 shows the same battery disconnect switch modification as Figure 5, only this time it is for a negative ground pedal.