This article will show you how you can add a expression pedal jack to just about any pedal that has room for a jack. This will require drilling a hole in your pedal so test fit and make sure before you drill.

The expression pedal jack will allow you to plug a TRS cable into the new jack and control a potentiometer (a.k.a. pot) with an external expression pedal.

What you will need:

2 -  TRS switched jacks. Typically we use 1/4" jacks but if space is a issue, you can use a 1/8" jack.
1 - Stereo TRS cable. One that is the right size for the jacks you use.
1 - Potentiometer. The same value and taper as the one in the pedal you are wanting to control.
1 - Enclosure for the expression stuff. A wah pedal or a simple box with a knob will do.

Now it's very important to not mix up the wires so I labeled them all with 1, 2, and 3 all the way across. Notice how the wires from the pots are wired to the lugs with the "arms" while the circuit board is wired to the "fixed" legs.

Inside the pedal:
To start, you will remove the potentiometer from the PCB that you want to also control with a expression pedal.
Then wire this pot to the new jack.
Connect new wires from the PCB to the other legs of the jack.

Inside the Expression pedal:
Solder wires from the pot to the jack legs.

One caveat to this is the Sleeve connection on some jacks is going to make contact with the enclosure. This means the sleeve contact will be grounded so if one of the pot connections in the original pedal is ground, swap things around so that the ground is on all the sleeve connections. If none of the connections are a ground connection, you will need to make sure the nut on the "Inside the pedal" jack doesn't make contact with the sleeve connection inside the jack. It's probably best to use a jack with plastic threads. Something similar to the Neutrik NMJ3HF-S.

The most common expression pedal wiring is to connect the pot to a 1/4″ stereo (TRS) instrument jack as follows:

CW (Lug 3) —— Sleeve
Wiper (Lug 2) — Tip
CCW (Lug 1) —– Ring

An alternative is with the tip and the ring reversed as follows:

CW (Lug 3) —— Sleeve
Wiper (Lug 2) — Ring
CCW (Lug 1) —– Tip

Mono (TS) cable/jack pedals often use:

CW (Lug 3) —— Sleeve
Wiper (Lug 2) — Tip
CCW (Lug 1) —– Tip

©Griffin Effects 2021