Sony CDX-A55 is a CD changer unit designed for in-car use. It can store and play up to 10 discs, and has a variety of features to enhance the listening experience. The unit has a built-in 8fs digital filter and 1 bit D/A converter for high quality sound, and it is compatible with a 4-speaker system. The CDX-A55 also has a number of playback options, including the ability to play tracks in order, shuffle, or repeat. Additionally, the unit has a memory function that allows users to store their favorite stations and recall them easily.