Equalizer

If the sound is enhanced with the iPod's software equalizer (EQ), some EQ settings — like R&B, Rock, Acoustic,indie, and Bass Booster — can cause bass distortion too easily.[11][12] The equalizer amplifies the digital audio level beyond the software's limit, causing distortion (clipping) on songs that have a bass drum or use a bassy instrument, even when the amplifier level is low. One possible workaround is to reduce the volume level of the songs by modifying the audio files