That the output impedance climbs to ~ 2 Ohms in the higher ranges was stated in a review from
www.hifinews.co.uk (in a printed/digital paper magazine, not online), along with backing up the Mojo's great measured performance that has already been proved by other magazines and sources with pro-grade measurement equipment.
Yep,
those are some unloaded and loaded measurements done by me on my German site in my four-part Mojo review (I'm too lazy to structure and translate it into English but my résumé is that the Mojo is an excellent device and while it doesn't do everything perfectly and could also be a bit more "aggressive" at times, it is darn good overall, somewhat addictive and I'm mainly using it as a DAC only for most IEMs with an additional low impedance, low noise Amp for various reasons, whereas I use it to directly drive some full-sized head-phones; and finally I wrote that if I had to rate it, it would get ~ 4.5 out of 5 stars from me), however I've also uploaded them here on Head-Fi:
http://www.head-fi.org/t/800208/the-rmaa-rightmark-audio-analyzer-source-and-audio-device-measurement-thread-measurements-in-post-3-tutorial-in-post-2/45#post_12803183
[rule]
Here are some measurements by another member months before I bought my Mojo, asking why there was some FR deviation under load:
http://www.head-fi.org/t/784602/chord-mojo-the-official-thread-please-read-the-3rd-post/4320#post_12058168
...
and Rob's answer to that matter:
http://www.head-fi.org/t/784602/chord-mojo-the-official-thread-please-read-the-3rd-post/4320#post_12058437
(and I definitely disagree to the quoted statement before Rob's reply that this behaviour is "definitely audible" with every in-ear, as it definitely is not, especially with those where the deviation starts above ~ 9 kHz.)