Here’s how it works. The best MP3 players transform your music to superior high-resolution sound, thanks to built-in digital-to-analog converters (DACs) and the fact that, well, they're not your ...

Case in point: MP3 players. Music downloaded and saved to iPods or ... If you have an old phone -- or you buy a new one without service -- you'll have access to the full realm of app-based music ...