And I sure would like to know a circuit to build that would absorb and effectively mute those pops.  On some pro-level equipment these days, there are built-in 'soft starts' and such that help to prevent voice coil damage when power to speakers is switched on...a helpful circuit to the budget as well as to the eardrums.  It surprises me tho that I couldn't find this Tone Port popping problem discussed on the Line6 site....or maybe I just haven't used the right search terms.  Hopefully, I'm not the only person in the world who's aware of the behavior and who also believes there needs to be a simple, quick way to eliminate the popping each and every time a Tone Port is rebooted while outputted to powered monitor speakers.

Now, please, don't everybody at once yell something like "well, turn the offended/offending speakers off while you're re-booting, stupid!".  Sure, that would work.

I certainly would do that very thing if my arms were 8 feet long and my hands were a half inch thick.  The speakers are mounted in an inconvenient location and it simply isn't practical to turn them off and on regularly...and in the presence of others who would wonder why killing the sound was even necessary.  So, my fellow players and recordists, here's my question: could I bridge the UX2's line-outs with some capacitors, chokes, etc. in order to absorb the energy that would otherwise go straight to the speakers' amps and in turn the speakers thus delivering to all ears on deck this very annoying and possibly dangerous popping report at somewhere well over 110 db in sound pressure?

I have imagined a number of workarounds for the problem but most wind up just becoming silly.  For instance, Hook a foot switch to a pair of spare solenoids robbed from an old pin ball machine.  Then fashion one of those to a linkage that would pull the 2 cables out of the UX2.  Then use the other solenoid to push the plugs back INTO the UX2.  Easy...one floor switch to cut the offending pops' signal, and the other floor switch for returning to the normal ON condition by slamming the plugs back into the UX2's Line Out Jacks.  Might be a fun project for my grandson's science and physics classes. But for my practical purpose, there has to be a better way.  What say yee?