VAMP's audiophile-grade, high fidelity DAC processor extracts the digital signal of the iPhone to bypass the iPhone's internal DAC.

ENGADGET: V-Moda VAMP for the iPhone: an analog converter and headphone amp with a $650 pricetag

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.

WSJ: Sonic Truth

Case in point: the Icon iDo integrated digital-to-analog converter (also called a DAC) and integrated amplifier is geared specifically toward Apple portable devices like the iPhone and iPad.

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