This RC11 box is a mini-size line volume controller, you can adjust volume quickly without using the music player.
Product design is pure volume level control, it does not affect sound quality or color added. (it has no amplification function)
Very conveniently to control volume to get a comfortable listening level.
Compatible with many devices and music system:
headphones/headsets, MP3 player, smartphone, PC computer, TV, amplifier,active speaker etc which have line out jacks