Putting it subtly, one could say I’m a rabid fanboy of the Digizoid ZO ‘portable subwoofer’. It is basically the best bass boosting headphone amp available.
The first version of the ZO wasn’t without some flaws, though, as I wrote in the review linked above. Being very good listeners, Digizoid took many improvement suggestions by users into account for their freshly updated model.
On the audio side of things, the new ZO2 should have less background hiss, should be better EMI/RFI shielded, the 32 processing steps should be more evenly spaced, and there should be no more clicks and pops at turning the amp on or off. The new housing is rubberized instead of glossy plastic, and the ZO2 now has a volume control, so it can be used with line-level outputs as well. Battery life is slightly improved, and a low battery indicator as well as improved shutdown handling have been added.
The ZO2 can be preordered from Digizoid – expect my review of it soon-ish.