BoomStick Psychoacoustic Portable Amp and Audio Enhancer - Silver Psychoacoustic audio processing that dramatically increases bass response, definition, and overall clarity Compatible with headphones, portable speakers, car stereos, and other audio devices that use 3.5 mm plug connectors Boom mode increases sound by 7 db, Boost mode increase sound by 11 db. The Boomstick does not have an independent volume control. Audio Input: connects to audio players via attached 3.5 mm cable Audio Output: connect directly to headphones with 3.5 mm plug, or car stereos and portable speakers via AUX