This is a common question regarding any ART products that have output level meters. If you use an XLR connection to a mixing board and phantom power is on at the board, the meter will read this voltage and the meter will be pegged at max.

Will this hurt the unit? Eventually, yes. The meter will burn out. While it’s bad form to have any voltage come into an output, sometimes your at a gig where the phantom power cannot be disabled on individual channels, it’s all or none. In these cases, a work around is to use the 1/4" output instead and use a good quality instrument cord to one of the boards 1/4" inputs since 1/4" doesn’t support phantom power.