While the advent of digital music allows everyone to listen to their own personally curated playlists wherever they go, it does present a problem: These audio files are compressed down to soggy versions of themselves, stripped of all rich subtlety and nuance. Most of us won't mind the difference, but for sound purists who are searching for more exact replications of their tunes, it's a constant struggle to find the right components – headphones, amplifiers – to elevate the aural pleasure.

For iPhone audiophiles who fit this description, there's the V-Moda Vamp, a $650 battery-powered, brushed metal and silicone case that contains a digital-to-analog (DAC) converter and a two-channel 150mW headphone amplifier that combine to transform your flat tracks into fully realized, hi-fi tunes (it also packs a 2200 mAH battery for charging your phone). A bulky, blinking thing that adds 135 grams to your iPhone, the Vamp has a top-mounted volume knob, a glowing three-position LED switch that cycles through sound/charge modes, and a headphone jack. There's also hi-lo-gain switch on the bottom, and a button on the side that, when pushed, displays battery level, and changes audio modes (Pure and VQ). Pure maintains the audio's original recording; VQ punches things up a bit.

What all of this amounts to is an on-the-go audio experience that even the most rigid music lover can appreciate. During our time with the Vamp, we listened to a wide variety of music, from Miles Davis and Metallica to Beethoven and The Black Keys. Every note, echo, strain, and solo sounded as if we were sitting in our armchair at home and hearing them on our $4,000 system. In other words, everything was warmer, and more well-balanced than the normally flat audio of our iPhone. (It must be noted that we listened to the Vamp with a pair of Sennheiser HD 700 headphones, which greatly complemented the acoustics; the Vamp demands high-quality headphones.)

Although it transforms your sleek iPhone into a monstrous thing as it transforms your music, the Vamp is a well-designed, high-quality device that soothed the ears of even the hardest-to-please music snobs we shared it with. It even started conversations with pretty much anyone we come across (one listener was asked why he brought a Geiger counter to a party; another if his police scanner picked up a good signal). It's certainly for a very specific person – the on-the-go audiophile who doesn't want to compromise his listening experience – but if that's you, the Vamp provides an unparalleled portable music experience. [$650; vmoda.com]