The Revolutionary Astell&Kern AK240 Hi-Rez Portable Media Player
Astell&Kern AK240 ($2500)
When I was in high school I had a big glossy poster of a bright red Ferrari against a dead black background in my bedroom. I lusted after it...I hoped against hope one day I could afford one...I never would. Oh well, that's the way of the world: Some people will have things that you never will. Get used to it.
Such a thing is the Astell & Kern AK240the Ferrari...hell, the Bugatti Veyron, of portable media players. The question is not whether the AK240 is worth $2500 for most peopleit's not, most people simply shouldn't be spending this kind of money on a player. This is a luxury/enthusiast item. The question is, if you've got the passion and money for these types of killer gadgets, does the AK240 deliver passionately on that money spent? Is this a worthy super-toy? In short, yes. This is excess at it's finest.
There's a lot of ground to cover, so I'll dig right in...
The AK240 boasts an aircraft-grade Duraluminum chassis that starts with a single 435 gram billet of the material. It then goes through a complex 12-step process of machining, finishing, anodizing, and laser engraving to complete the finished enclosure. A full description of the process can be found here. The result is a flawless deep champaign finish; a brilliantly durable exoskeleton; a drop-dead gorgeous piece of kit in hand.
Speaking of "in hand", my first thought on seeing this unit was "gorgeous"; my second thought was this thing might be uncomfortable to hold. I've not found this to be the case. In part, the leather case (pic next page) softens the angular shape, and in part the position of the volume control is much more ergonomic than it might appear, but I think in the end it never bothers me because my mind never really gets too far past that on-going initial impression, "My goodness, this thing is gorgeous."
A 3.31-inch AMOLED WVGA (480 x 800) touch-screen display is a tad smaller than most smartphone displays, but provides plenty of space for comfortable control in use, and at maximum brightness is easy to read in full sunlight.
The rear of the unit is spectacular with a carbon fiber panel under a deep gloss finish. The play of light on the warp and weft of the material give a distinct impression of depth. The metalized Astell&Kern logo on the rear panel seems to float 1/4" above the carbon fiber panel beneath...a luscious optical illusion.
The top panel includes a 3.5mm headphone jack that alternatively functions as an analog line out and Toslink digital optical output; a 2.5mm TRRS (tip-ring-ring-sleeve) balanced headphone jack; and the power button. One note here: the DSD format is not supported when using the optical output, and the optical output is unavailable when the AK240 is used as a USB DAC.
If you've got headphones on and turn on the line-output function the output goes to full volume and cannot be adjusted by the volume control, so you might get your ears blasted if not careful. If you've got normal Toslink cables and want to use them with the AK240, you'll need one of these adapters.
Balanced headphone drive is a special method for driving headphones that removes he common ground and reduces cross-talk found with normal headphone connections. For more info see this page. The AK240 is fairly new, and balanced 2.5mm connections are rare; I've not been able to find anyone with a hearty range of adapters for this balanced output yet, but no doubt ALO Audio, WyWires, and Moon Audio will be developing a range of solutions. Give either one a call and I reckon they'll have a solution quite soon.
The power button takes a "long push" to turn on and off; a short push while on will turn the display on and off. When off, holding the power button in for longer than 12 seconds will trigger a complete re-boot of the player. I did have one instance of it locking uppowering it down and then re-booting had back in operation quickly.
Track control buttons on the left-hand side of the player are responsive and intuitive for audio enthusiasts with a standard push to track forward and hold to fast forward method. It's the details that count with a luxury product. The buttons are small with elegant < l> > glyphs; their actuation clicks nicely at the tip of your finger; and the function of the buttons while inside the leather case remains flawless.
A microSD card allows for 128GB memory expansion to the 265GB internal memory. Astell & Kern recommend SanDisc Transcend memory cards. Once inserted, the SD card will be mounted and scanned for music. Music on the card will appear on song, artist, genre, and album lists along with track in main memory; the folder view changes to display "SD card" and "Internal Storage" as the initial navigation step.
The Micro B USB connector on the bottom panel allows you to charge the device; transfer files; and use the AK240 as a USB DAC. Transferring files and using the AK240 as a USB DAC is not entirely plug-n-play; depending on whether you're Mac or PC centric the procedures differ, for full information see the manual. I did try file transfers and use as a DAC with both Mac and PC machines; set-up was painless and operation smooth. Note: when used as a USB DAC EQ controls are disabled.
Also on the bottom panel are a couple of small Torx screws presumably for taking the unit apartnot going to do that, nopeand a laser engraved serial number.
And lastly the right side where, it seems, all the post-modern angles of the AK240 collide to form a bastion of security around a humble, knurled rotary volume control. As unfamiliar as this configuration might look, it worked and felt completely natural in my hands...and more so when in its leather case. I found myself generally using the knob for fine adjustments and my finger on the display for larger ones. The drop-down notification bar does have a volume lock which allows you to select whether or not the volume control is active when when the display is off. I mowed the lawn a few times with the AK240 in my pants pocket without the volume locked and had no problems with inadvertent volume control changes.
Specs and Functionality
Where do I start? It would be easier to describe what the AK240 doesn't do. Let's start with the specifications list:
Of particular note are the Cirrus Logic CS4398 dual DACs and the unmentioned custom XMOS chip that allows the AK240 to play DSD files natively. As you can see the list of file formats supported is quite comprehensive.
Output impedance is stated as 1 Ohm. I manually measure the output impedance using a 500Hz .WAV track. Full volume open circuit voltage of this track was 1.07 Vrms. Placing a 32.5 Ohm resistor across the output to ground reduced the output voltage to 0.973Vrms. This calculates to 3.24 Ohms. Measured resistance of probes and connections was about 0.3 Ohms. Out of interest I measured the AK120 I have here and got essentially the same figure at 3.29 Ohms.
Music Sources - Obviously, the AK240 can play files stored on the 256GB of internal memory or the up to 128GB external microSD card. As mentioned previously, it can act as a USB DAC/headphone amp. And it can stream music from a host computer on your network, though it will not stream directly from an NAS drive.
To use the MQS (mastering quality soundAstell&Kern's term for hi-rez files) streaming function you'll need to load the MQS Streaming Server software onto a Mac or PC in your home. I installed the app on a PC and mapped the Bluesound Vault drive as a virtual drive on that machine. Once the app was installed I selected the mapped drive as the source for music and it worked beautifully. Initial set-up will take a little while as the MQSSS software will spend some time indexing all the tracks.
Music Outputs - As mentioned above the player's headphone jack can drive a headphone, can act as a line-out (latest firmware has additional line-out select on the volume control screen), and a Toslink digital output.
The 2.5mm jack will drive balanced headphones. I'm a little leery of using a 2.5mm jack for balanced cans as they're somewhat fragile and the adapters that will be created to couple this jack to the various balanced connectors will likely be somewhat heavy. I suggest strongly that adapters made should have a long enough cable so you'll be able to handle the player with the adapter/headphone connectors remaining on the table. None the less I do undertand the need to make the balanced connection a different size than the standard 3.5mm jack so as not to confuse folks or allow the wrong type of connector to short out the contacts. C'est la vie.
The AK240 can also act as a Bluetooth v4.0 A2DP source. The previous Bluetooth implementation on the AK120 was very poor in my experience; the AK240 Bluetooth connection performed flawlessly. I know it might seem a little silly focussing in on the Bluetooth performance of a hi-rez player, but I think it's terrific to have when on the move and using a portable Bluetooth streaming speaker. The AK240 will not transmit DSD files over Bluetooth, and Astell&Kern recommends files of 48kHz sampling rate or lower for drop-out free playback.
Playlists - A huge improvement here over the AK120, the playlisting functionality of the AK240 is superb! Just press and hold your finger on any song, album, artist, folder, or genre; when the item shows ready to drag and the display changes to allow you to drop the item into a play list; the display switches and you select which playlist you want the item on. In other words two swipes of your finger and you've added what ever you want to a playlist.
The 10-band graphic equalizer is also a solid improvement over the AK120s 5-band. The EQ has an interesting UI: you can either just draw an EQ with your fingertip across the screen, or you can adjust the sliders one at a time. I found both modes a bit hit and miss. The drawing mode seemed to not quite accurately enough follow my finger tipnot sure whether it was my drawing skills or inaccuracy of the UI, but I always had to go back and adjust it slider by slider after my first course pass with my fingertip. And the slider by slider mode was made difficult by the accuracy with which you need to touch each sliderif you miss, the AK240 thinks you're drawing a line and the sliders move around somewhat erratically. Though it was a bit difficult I did always manage to get what I wanted in the end; EQ profiles can be stored and easily switched between after being saved.
One thing to note: when the EQ is turned off on the drop-down menu it significantly changes level which can shift the perceived EQ a bit. I thought it might be reverting to the ProEQ setting, but that doesn't seem to be the case.
The graph above was taken using a white noise track I have in my test tracks and my AP2522 acquiring FFT FR data. The overall upward slope of the curves may simply be a miss-calibration between the noise and my FFT settings and I think should be ignored as an absolute measure. Because this is a measurements of a noise signal it was averaged over 64 measurements and then significantly smoothed to reduce the noisy nature of the data and so that the larger EQ differences are readily apparent. It should be a reliable indicator of FR differences between EQ settings. As you can see switching between a FLAT setting and turning the EQ off gives a pretty healthy (~3dB) increase in gain, but does not show any significant changes in EQ. The Pro EQ setting does have a broad increase of about 1.5dB in the mid-range, and possibly (because this could be just a noise artifact, but I doubt it) a slight lift in the top octave. Generally speaking, I preferred the unit set to flat or drawing a custom EQ rather than use the Pro EQ setting.
Over-the-Air (OTA) Updating
The beauty of a highly programmable device like the AK240 is the ability to upgrade and add functionality over time through software upgrades. While it wasn't big on my list of features I saw many comments in Head-Fi threads about the AK240 where people desired finer grained ability to sort lists presented in different ways. The AK240 currently doesn't have a lot of control over list sorting. I thought they were interesting comments though, and I suspect it's exactly these types of issues (things that people comment on) that Astell&Kern are looking at when developing ongoing software updates to the player.
I've set my AK240 to connect to my wi-fi on start up, and twice now I've received notifications of a software update available on the device. In both cases it was knuckle-head easy to push the button and let the AK240 reload it's brain and get a bit smarter. Didn't notice any changes the first time, but the second time I did see a "line-out" button appear on the volume control screen. Made me feel like I have a product that's just going to keep geting better and better.
Okay, turn the page and I'll talk about my two favorite things about the AK240: its user interface, and the sound quality.