From what I can find, the Line 6 EX-1 seems to have a 10K linear pot (good), but connects with a TS cable? You’re getting a full sweep, so you might be able to tweak the wah to what works for you, using the 2nd page of Parameter Mapping [6.4.1].
https://cdn.eventideaudio.com/manuals/h90/1.3.0/content/edit-modes/parameters.html#mapping