So, Leeds...
I just remembered a minor physical design issue with the X3 Live that I ran into several years ago. But, don't worry. It's not a huge deal and I'll show what to do about it.
Here's a shot of my whole X3 Live rig. I use a second expression pedal and a little switch box that I made to allow me to switch guitars quickly.
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The design issue I mentioned will only be a potential problem if you play outside in the bright sunlight and if the sun is at the correct angle.
The reason is that the built-in expression pedal works in conjunction with an optical system inside the unit. The pedal essentially operates a light interrupter that gradually blocks light from an LED inside the unit from being "seen" by an opto-detector. This is very effective and eliminates the potential for dirty pots.
The problem is that if the sun (or other bright lights) get into the unit, the light will play havoc with the opto-detector and you'll essentially lose control via the foot pedal. Unfortunately, the hole where the interrupter enters the unit is not especially well-shielded from external light.
This actually happened to me several years ago during a sound-check at an outdoor event. Needless to say, it was a very nervous several minutes while I tried to figure out what was going on!
The fix is to block outside light, and this can be done with black gaffers tape.
First, tape over the pedal, covering the holes in the pedal, as in the pic below. This blocks light from entering the unit through the holes in the expression pedal if you take your foot off the pedal.
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Lastly, use some gaffers tape to make a little "light dam" to block light that may enter from the front, as shown below:
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The tape you see on my X3 Live in these pics is the same tape I put on it years ago when this first happened to me. It's been effective ever since.
Just a little hint that may come in handy!