TRS-RTS Wiring on Expression Pedals

Most expression pedals use a TRS cable/jack (Tip, Ring, Sleeve), like a stereo ¼” cable.
The common wiring is:

As you move the pedal, the resistance between the tip and ring changes. The device you’re controlling (keyboard, pedal, synth, etc.) reads the change in resistance, relative to the ground, and translates it into volume, wah, filter sweep, or whatever parameter is assigned.

Here’s the big challenge with expression pedals: there is no universal standard for wiring. Some manufacturers wire the resistor (wiper) to the tip, others to the ring, and some don’t use the ring at all. This means an expression pedal that works perfectly with one device might behave backwards or not at all with another unless it’s compatible or switchable. To make matters worse, sometimes this switch is labeled as “polarity” because they’ve swapped the Tip and Ring, but other times the “polarity” swaps the Ring and Sleeve, so it’s the heel-toe sweep that reverses, not the wiper connection point.

The Sybil accounts for this by giving you the option to choose the TRS or RTS on a switch inside the enclosure. If you plug your expression pedal into the Sybil and things aren't sounding quite right, you may need to hit the switch inside.

Here’s a quick rundown of the most common expression pedals and their wiring.
(Tip: TRS = TIP-ring-sleeve, RTS = RING-tip-sleeve. The Sleeve is always ground.)