From the maker’s site:
It sounds downright incredible, but this pedal doesn’t stop there!
The DoubleTracker Stereo features two modes of operation: SYNC and COMP, as well as a fast-action preset and our super-easy-to-use EXP jack. More on these features below:
When in SYNC mode (indicated by Red LEDs), the DoubleTracker Stereo’s 2nd voices are matched in tune, and when set to COMP mode (indicated by Green LEDs) as one voice raises in pitch, the other lowers in pitch (and vice-versa). COMP Mode dramatically increases the stereo field (a direct result of a phenomena known as the Haas Effect), and with a modest (or extreme) Spread setting, the sound can best be described as: Ampitheatric. Almost like an instant arena.
Using the preset is a snap: Simply dial in your favorite settings and press the SAVE button once. The Preset LED will blink three times and your preset is now saved (for up to 42 years!!) and can be toggled on or off instantly, at any time, by pressing the PRESET footswitch.
If the preset wasn’t easy enough, you’re gonna LOVE the EXP option.
To use an external expression pedal, simply connect your favorite expression pedal (following the connections below) to the EXP jack and turn the desired control(s) to the “EXP.” marker found at the terminal end of their clock-wise rotation. The control(s) are now assigned to expression pedal duties.
Its that easy.
To resume knob control, just turn the knob away from the EXP. marker. Yes, it’s that easy, and you can change which control(s) are assigned to expression pedal duties at any time, on the fly: in real time.