Correction: The Ernie Ball VP Jr is technically a volume pedal, so the signal needs to go between the guitar and the amp with mono TS cables (Volume pedal config, with the potentiometer in series, as a voltage divider.
But it can ALSO function using only one TS cable rather than two and here it would just be making a simple 2-contact variable resistor. Two birds, one stone as they say… Great pedal…
Just wanted to be thorough…
Maybe be careful with TRS 1-cable-style expression pedals, unless you want to be playing around with TRS-TS adapters or solder…