One other thing, I modified the Ernie Ball volume pedal for use with the Helix. In stock form, the pedal has a 250 K Ohm audio-taper pot and is intended to be used in the audio path, usually between guitar and amp.
However, the Line 6 is looking for a 10 K Ohm linear pot. What's more, unlike many expression pedals, which use a TRS (tip-ring-sleeve) 1/4" plug, the Line 6 is looking for a simple TS (tip-sleeve) connection, like a standard guitar pedal patch cord.
So, I hunted around on the Mouser website until I found a suitable and heavy duty 10 K Ohm linear pot and I wired the pot according to this schematic:
Of course, that would mean that I'd have blank holes in the front of the Ernie Ball pedal due to the unused jacks I removed. So, I made a new faceplate from pick guard material and affixed it to the original mounting plate with a few dots of hot-melt glue.
Here it is all in place:

This works flawlessly with the Helix.
One really cool thing about the Helix is that you can tell the Helix what kind of behavior you want the pedal to have. So, even though this physically has a linear pot, within the Helix you can tell it to use either linear behavior or logarithmic (audio taper) behavior for the pedal. You can do this on a patch-by-patch basis.
It's quite cool.
Another nice touch is that as soon as the Helix detects that you've plugged an expression pedal into the EXP 2 jack on the Helix, it automatically assigns that pedal as the volume pedal and it assigns the built-in pedal (EXP1) as a wah pedal (or whatever else you may have previously set EXP1 to control). You can change this if you want to, but this default setup is exactly what I want, so that's a nice thing, as well.
However, the Line 6 is looking for a 10 K Ohm linear pot. What's more, unlike many expression pedals, which use a TRS (tip-ring-sleeve) 1/4" plug, the Line 6 is looking for a simple TS (tip-sleeve) connection, like a standard guitar pedal patch cord.
So, I hunted around on the Mouser website until I found a suitable and heavy duty 10 K Ohm linear pot and I wired the pot according to this schematic:
Of course, that would mean that I'd have blank holes in the front of the Ernie Ball pedal due to the unused jacks I removed. So, I made a new faceplate from pick guard material and affixed it to the original mounting plate with a few dots of hot-melt glue.
Here it is all in place:

This works flawlessly with the Helix.
One really cool thing about the Helix is that you can tell the Helix what kind of behavior you want the pedal to have. So, even though this physically has a linear pot, within the Helix you can tell it to use either linear behavior or logarithmic (audio taper) behavior for the pedal. You can do this on a patch-by-patch basis.
It's quite cool.
Another nice touch is that as soon as the Helix detects that you've plugged an expression pedal into the EXP 2 jack on the Helix, it automatically assigns that pedal as the volume pedal and it assigns the built-in pedal (EXP1) as a wah pedal (or whatever else you may have previously set EXP1 to control). You can change this if you want to, but this default setup is exactly what I want, so that's a nice thing, as well.


