Pros: Improved DAC section and especially amp section, powerful and more refined overall, low noise, improved volume knob
Cons: Nothing major.... async USB would be nice I guess.
The Audinst HUD-mx1 compact DAC/headphone amp was a great little unit. It also happened to be one of the very first reviews that I did at HeadFi. In the subsequent years I've gone on to review dozens of other products from amps to DACs to headphones and more, and I also went on to become something of a "real" reviewer at InnerFidelity. Through all that, I've never stopped recommending the Audinst mx1 as a cheap, reliable unit that sounds good and doesn't take up much space.
There is slightly more free space here compared to the mx1, due to the widening of the board,
required to fit that extra front panel switch to select USB or Toslink:
The new headphone section:
The new differential amplifier for the DAC section:
The actual DAC chip:
The AKM receiver, TXCO clock, and VIA USB chip