Visited iRiver's office this weekend. Thanks to Jimmy and Owen for having us over.
More detailed specs than is listed online. USB-DAC function worked great with my Windows 8 Pro Tablet (not RT). No drivers needed, was just recognized.
Size comparison, Left to right, AK100 -> AK120 -> HM-901. Kind of reminds me of an AT&T commercial. More bars in more places.
iRiver's demo Set up. They had some top end full sized headphones there. Most notably, the Sennheiser HD800 and Audeze LCD-2 (Rev 2)
I brought my JH-13 (1st gen). The HM-901 definitely sounded better, but only clearly better sounding if I used much higher end headphones, like the LCD-2 or the HD800. Also, the HM-901 has a more powerful and better Amp section, so that could be contributing to the better sounds quality as well. But my 1st Gen JH Audio JH-13's are not high end enough for the AK120 and HM-901. My preferred headphones are the HE-6, which the HM-901 can barely power, and the AK120 can't manage at all.
The sound quality difference between the AK100 and the HM-801 in the previous generation was a larger gap. But with the new generation of the AK120 vs. the HM-901, the gap is much smaller.
Overall, I really loved the all-in-one functionality of the AK120. The addition of Asynchronous USB DAC functionality is a real bonus. No need for extra dongles, docking station, etc. If I traveled all the time, the AK120 would be my #1 rig. But for occasional travel and mostly at the office and at the home use at a computer / workstation / cubicle office set up, the HM-901 still wins in my book, especially when used with Full Sized Headphones. For high end custom IEM use, the AK120 seems to be the best choice. For High end full sized headphones, the HM-901 is clearly better.
But is User Interface is another issue, where iRiver and the AK120 are the clear leader. The HM-901's user interface is much much slower and more cumbersome to navigate.
But the biggest minus against the AK120 is the price. At $1300, costing almost twice as much as the AK100 is quite ridiculous. If it were the same price as the AK100 or marginally more at sub $800 USD, I'd buy one in a second. But at $1300, that gives me major pause.