There are other models in the range, including an ultra portable headphone amp called the iBasso T4 (it is VERY small and weighs just 29 grams) and a high end model that comes with various types of Op-Amp to swap over to alter the sound signature (one for the perfectionists).
The iBasso D2 works especially well with higher impedance earphones such as the Sleek Audio SA6 and Klipsch Image X10, where there is good improvement in depth of bass, as well as high frequency detail and soundstage. I’ve yet to test with lower impedance earphones (Ultimate Ears Triple.fi 10’s, etc), but I would guess the effect is similar, but maybe not so pronounced.
Below is a photo of the iBasso D2 with my Sleek Audio SA6’s and an old iPod Nano:
In my opinion the most interesting application for the iBasso D2 is using the DAC with a laptop. With my IBM ThinkPad T62 laptop feeding the D2’s DAC and a pair of Sennheiser HD650’s the difference in overall sound quality is significant compared with the laptop’s standard headphone output. I would say this is the application where the biggest improvement in sound quality is seen.
More Information
For the range of iBasso headphone amps, including the iBasso D2 and iBasso T4, please visit the HiFi Headphones shop.