Thatonenoob posted a review of the HUD-DX1 DAC/Amp on Head-Fi. According to the review it is a pleasant sounding unit with optical input and RCA line out. This is unusual for sub-$400 portable DAC/Amps. It also support DXD/DSD native.
Pros: DSD/DXD Capable, Musical and Engaging, Nice Trim
Cons: Gain Switch Lacking, True Lineout, Not Airy
Dave has posted a review of the Audinst HUD-DX1 over on Headfonia. He felt it was lacking in some areas for a product at the $400 price point.
Review of the DX-1
Project86 has posted a review of the Audinst HUD-DX1 DAC/Amp on Head-Fi. Price point is just under $400.
Pros: Bold, lively sound from the DAC portion, headphone amp powerful enough for planars, rock-solid stability over USB
Cons: Gain is too high for some headphones and especially IEMs, price isn’t as low as I’d like
Review of the HUD-DX1