Today, I've been listening to the AK240 for the first time outside of a show environment--right now (as pictured) with the OPPO PM-1 (a more recent prototype of the PM-1 than the RMAF one)--and it is...just...wow. In terms of performance, features, user interface (which is responsive, intuitive, and has search), the AK240 is well beyond an evolutionary step above the AK120, which I have and love. Whereas I often use my AK120 optically connected to a CEntrance HiFi-M8 LX, I strongly suspect I’ll be using the AK240 far more often—and maybe exclusively—on its own. Versus the AK120, the AK240’s specifications show a more powerful amp section. While that’s certainly part of the equation, there seems to be more to it, as the AK240 via its headphone output has a more detailed, more full sounding presentation with the different headphones I've pushed with it so far—it’s unquestionably better.
Astell&Kern also sent their new AKR02 in-ear monitor, which, like their first IEM, is being offered in partnership with Final Audio Design, but this one based on Final Audio Design's high-end FI-BA-SS model. (I don't have the FI-BA-SS, so I can't tell you what the differences are between it and the AKR02.) My understanding is that the AKR02 was tuned for use with the Astell&Kern players, and though I'm not sure what that entails, the AK240/AKR02 combo sounds to me like a very potent, pocketable high-res system. (I expect the AKR02 will also work well with my other non-Astell&Kern portable setups, but I haven't tried it with any of them yet.) I'll have more to say about the AKR02 after more use.
In terms of its design: at CES, I wasn't quite sure what to expect of the AK240 ahead of my visit to Astell&Kern's exhibit. Every photo I'd seen of it confused the living daylights out of me--the design is hard to "get" until you actually hold it in your hands. At least to me, the photos were very confusing. Once in hand, though, the design really does make sense. We shot a video of it there, showing it in-hand, but the lighting wasn't great. We'll be shooting a video of it in the studio, spinning it around in-hand, and you'll see what I mean--video should help you understand what's actually going on with the design a lot more than photos have so far done.
In hand--in person--the AK240 is actually a very attractive, very striking design, to my eyes. The initial photos I saw made it look a lot chunkier than it is. In my hands, it doesn't look or feel chunky to me, though it is thicker than their previous models. Here's a size comparison photo, showing its size compared to other devices. (From top to bottom, Astell&Kern AK120, AK240, iPhone 5S, HiFiMAN HM-901, Chord Hugo.)
I haven't yet directly compared the AK240 to any other players other than its AK120 sibling, but I will.
Early reservations I have include price--I'm not sure what the MSRP is going to be, but I get the impression from the numbers I'm seeing in this thread that it's going to be very expensive. I also am not crazy about the choice of a 2.5mm jack for the balanced output. While time may prove my concerns about the 2.5mm jack unjustified, I'm just having a hard time envisioning some full-size headphones and their hefty cables terminated in 2.5mm, without at least the potential for issues; and with a balanced output, I think there'll be many who want to drive full-size headphones with it.
(I haven't used the AK240's balanced output since CES, but I will soon--Moon Audio made me a balanced 2.5mm end to go with my Moon Audio adapter cables, and that'll allow me to use several of my headphones balanced with the AK240.)
Outside of those concerns, so far the AK240 has been nothing but amazing. I still have a lot music and a lot of headphones to try with it--and I haven't yet tried it as a USB DAC--so there will still be much more to say about the AK240 going forward. (We'll start with a CES highlights video we're working on now.) So far, though, like I said: Wow.
UPDATE 014-01-26 18:48 EST: Quick notes, including firmware update, DSD playback, self-noise (or complete absence of it),...(click here).