As a test, I downloaded files from HDtracks.com, an online retailer specializing in hi-res audio, plugged a device known as a digital-to-analog converter (DAC) into my computer and listened over earphones.
Up until this week, this particular piece of circuitry was the title holder for "world's thinnest smartphone, " measuring in at 6.55mm thick. (The Alcatel Idol Ultra now claims this title at 6.45mm, although it's technically not on sale yet.) Despite the small package, it also professes to pack a hefty audio punch, boasting a pair of Beyerdynamic MMX 71 iE earphones and Cirrus Logic CS4398 DAC.