If you paid top dollar for hi-fi speakers for your MP3 player, why do your tunes still sound decidedly lo-fi? It's because the audio output still depends on the quality of the music files you use. The quality of a file is determined by its bit rate, the number of kilobits per second used to store the audio in a digital format.
An uncompressed music file from a CD has a native bit rate of 1400 kbps, but most audio programs such as iTunes rip MP3s at a default rate of 128 kbps to keep file sizes small. If you have a discerning ear, you should consider ripping at a higher bit rate such as 160 kbps, 192 kbps, or even lossless.
The resulting files will be larger but will sound noticeably better. And before you spend a small fortune building a legal library of downloaded songs, make sure that the audio quality of your online store of choice is high enough to take advantage of your new digital music speaker system.
