The perfect tool for connecting smartphones, laptops and computer outputs to a front-of-house system or other professional sound setups is the Sescom AUD-TRS-BAL. It's a passive audio interface used to convert 3.5mm TRS line-level audio to left and right XLR balanced left/right outputs. Simply stated, it converts the output from laptops, MP3 players, CD players and more to interface with professional balanced 600 Ohm (relative) systems such as powered speakers, mixers and audio workstations.
The AUD-TRS-BAL also works great in school auditorium or similar projection setups where the video source from a laptop needs to be sent to the projector but the audio needs to connect to a separate sound system. The unit is housed in a rugged aluminum enclosure and integration is simple with its attached 6" breakouts for all connections - no adapters needed!