Fostex’s HP-P1 Headphone Amplifier & DAC is intended to sit between your audio player and your ears and skip the cheap analog path in preference of all digital signals.  That is of course a vast simplification of digital to analog conversion, but your ears are the deciding factor here.  It uses the dock port, which allows you to completely bypass any possible changes to the raw digital signal by your iThang and gets the pure digital signal that ultra-high end headphones need.  TechPowerUp was impressed, but you do have to be quite the audiophile to send $700+ on an DAC … whether it is technically worth it or not.

"Fostex’s newest product is a headphone amplifier and DAC dubbed the HP-P1. The HP-P1 offers a fully digital connection to any newer iPod or iPhone. Its ability to read digital data from the device is a unique feature that promises maximized audio quality because it bypasses the cheap analog hardware in the i-device."

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