AudioQuest's Dragonfly USB DAC

The AudioQuest DragonFly USB DAC is run in asynchronous USB mode thanks to Gordon Rankin who designed the DragonFly's circuit (i.e. everything except the industrial design) and its based on the 24-bit ESS Sabre™ DAC. Musical data up to 24/96 (limited to avoid the necessity of downloading drivers for Windows users) is passed from the Texas Instruments TAS1020 USB receiver chip to that ESS Sabre™ chip via I²S and this bus-powered USB thumb drive-sized DAC includes an analog volume control that takes control of your Media Player's (like iTunes) volume slider so your music doesn't lose any resolution as you adjust the level.

It will glow green for 44.1, blue for 48 and amber for 88.2 kHz.
Price: $250