Swap audio channels? Is there a way to swap the audio channels coming out of the headphone jack on my tablet? A third-party app would be acceptable.

For some context: My tablet has a pop in the left channel and I need it to pop in the right instead. I'm using the left channel to play background music through a large PA system and the right channel with notes to myself that only I can hear. I separate the left channel out to the PA and then plug them both into a mixer for myself. The PA gets the left (with the pop) and I get both. Since the pop is only in the left, if I could swap the channels, I could just swap my external wiring and voila, only "I" hear the pop, not the PA system.
The pop is most certainly because of a hardware fault, which may or may not be in your tablet. Does it pop with other headphones too? If not, throw away the faulty headphone. If it does, then indeed the tablet is faulty and you should see if you can get it repaired under the warranty.

Anyway, it will not be solved by swapping the audio channels (the pop will stay in the same channel). Also, such an app is very unlikely to exist (as it is very rare for somebody to want to swap audio channels), and even if it would exist, it would need at least root access if not outright recompiling the kernel.

If I were you, I would make a jack extension cable with crossed left and right leads. If you can't, ask a friend who is experienced in soldering. It may also occur that you can swap the channels without soldering; for example if you use a Jack-RCA converter, you can simply swap the white and red plugs.