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Astell&Kern AK240

The consumer electronics industry has always evolved at a rapid rate, but the frantic pace of innovation, new product introductions, and price escalations in portable high-performance audio is now outdistancing anything I’ve witnessed before. Take Astell&Kern as an example.

Two years ago there were no Astell&Kern products on the market, as A&K was merely a glint in corporate parent iRiver’s eye. One year ago I reviewed Astell&Kern’s first product, the AK100, which at the time was the most expensive portable player available. Now, the AK100II has replaced the AK100, and the AK100II is A&K’s entry-level offering. The new AK240 is A&K’s current flagship model. At over three times the price of the AK100II the AK240 ranks as the most expensive portable player on the market. If you purchase one, and you lose it, you will have at least 2495 reasons to feel very, very sad.

Technical Tour & Ergonomics
The AK240 crams an amazing amount of technology into its duraluminum chassis. The chassis itself begins as a 435-gram billet and goes through a twelve-step process that includes laser-engraving the finished enclosure. This level of attention to detail carries through to all aspects of the AK240’s design, including its shape. Two of the AK240’s four corners are cut off. At first I thought this might have been a sly nod to the TV series Battlestar Galactica (the new one, not the original) where all the papers have cut corners. But the cut-corner design is purely ergonomic—when you pick up an AK240 your pinky naturally wraps around one cut corner while your thumb rests on the other. The AK240 feels great in your hand with just enough heft to feel substantial without being overly heavy.

Inside the AK240 A&K you will find not one, but two, Cirrus Logic CS4398 DAC chips, one for each channel. The AK240 supports PCM rates up to 352.8/24 and DSD up to 128x. It also supports all formats including FLAC, WAV, ALAC, AIFF, MP3, OGG, APE, AAC, DFF and DSF files.

The AK240 is not only a portable player, but also a USB DAC and Wi-Fi and Bluetooth portable streaming device. What’s interesting about this dual-streaming feature is that unlike most streaming via Bluetooth, which goes from your smartphone or player to your home music system, the AK240 also streams from your home computer’s music library to the AK240. The idea, I assume, is that while you mop the floor or vacuum your bedroom you can be listening to anything in your main music library via headphones, not merely what is in the AK240’s 256GB internal memory or removable micro-SD card (provided that the AK240 shares the same Wi-Fi network as your computer).

The AK240 has a 3.32-inch AMOLED WVGA (800×480) touchscreen display that functions not only as a display that supports full-color graphics but also as a multifunction control surface. In addition to the screen’s controls the AK240 has a single pushbutton on top for wake-up and on/off, plus “forward,” “pause/play,” and “back” mini-buttons on the side opposite the volume control knob. The volume knob is large and more sculpted in shape than the AK100’s volume control. The case has protection on either side of the knob that reminds me of a Panerai wristwatch.

I found the AK240’s volume control to be much twitchier than the AK100’s control. If you want to increase the volume rapidly on the AK100 you merely turn the knob quickly, but if you try to increase the volume on the AK240 the same way, the control often takes the volume down instead of up. Only a smooth, slow touch would consistently yield “up” when I wanted up. But down was never a problem.

Unlike the original version of the AK100, which came with no case, the AK240 comes with a custom-fitted leather case available in a variety of colors. I know that it is expensive because I bought one made by the same company for my AK100, and it set me back $80 for a much simpler design.

When I used the AK240 as a portable player I inserted the same 32GB micro-SD cards into the AK240 that I created for the AK100. The AK240 can take a while to read a fully populated card. Some patience is required when you put in a new card because it will not play any of the files on the card until the card has been fully scanned. Unlike the original AK100, which has two SD card slots covered by a sliding click-lock door, the AK240, AK120, and AK100II all have a single SD card slot with no door. I understand that since the current series of A&K devices can accept a much larger card than the original AK100 the need for two slots isn’t as great, but having two slots and the sliding door was and is a nice feature on the AK100 which I miss on the AK240.

There are many unique playback options in the AK240 and some can trip you up. If you select MQS or DSD instead of “All” from one of the AK240’s sub-directories, the AK240 will not show you anything (or play anything) but MQS or DSD files. When this happened the first time, after I had just finished using the AK240 in streaming mode, I thought I had “broken” another component under review (which occurs more than you would think), but after a couple of e-mails with A&K’s technicians we figured out I had somehow gotten into DSD mode. My bad.


Like the AK100, the AK240 has built-in EQ features. But unlike the AK100 you can create and save your own EQ settings. If you wish, you can have a unique EQ setting for each headphone or music genre that you regularly use. Frequency points include 30, 60, 120, 250, 500, 1k, 2k, 4k, 8k, and 16kHz. I don’t recommend trying to set your EQ on a moving train or bus— the touch controls are quite sensitive, and it’s far too easy for a 0.5dB adjustment to turn into 5dB one if you aren’t careful where your fingers go. Also, if you listen primarily to DSD material you will be disappointed to discover that the EQ features are not active with DSD files. One ergonomic area where I found the AK240 to be glitch-free was firmware updates. The AK240 has built-in Wi-Fi. When Wi-Fi is turned on from AK240’s setting menu, it also activates the automatic detection of firmware updates. When A&K releases new firmware, the AK240 will let you know and give you the option of downloading it. (This sure beats having to download new firmware to the main directory of your device by USB connection from your computer for the firmware to begin the update process, as is necessary with the AK100.)

You have several output options with the AK240. First and probably most-often used is the single-ended headphone output via the mini-stereo plug. For most headphones or DAC/pre applications this is the go-to connection. This mini-stereo input can also serve as a digital TosLink output, so you can use the AK240 as a USB-to-TosLink digital converter if the need arises. The TosLink output supports PCM up to 192/24, but will not pass a DSD signal, at least not yet. You never know what future firmware updates will bring. The last output on the AK240 is the balanced analog output using the four-conductor 2.5mm connector. It was included so you can drive some power-hungry headphones in balanced rather than single-ended mode.

Day-to-Day Use
When I received the AK240 initially I had some issues with streaming. Playing DSD, high-res, and Red Book WAV files was no problem, but the AIFF format was a no-go. The Version 1.15 firmware update fixed that problem completely. With the current firmware in the AK240 and the latest version of the streaming app on my main computer, the only issues I had were a result of signal-strength loss. Sometimes as I wandered around my house with the AK240 in streaming mode the music would stop, but if I moved to an area with higher Wi-Fi signal strength the music would begin once more. The incidence of dropouts was not related to the density of the music file—dropouts with DSD files were no more frequent than with a 44.1/16 file.

Used as a DAC the AK240 had no problems decoding everything I threw at it. When I used Audirvana Plus as the playback app with the AK240, I had the option of either DCS or DoP [DSD over PCM, a method of transmitting DSD data) 1.0 over PCM, and both supported up to 128X DSD with no down-conversion. I noticed only three potential issues when the A&K was used as a DAC. First, the AK240 gets hotter in DAC mode than it does when used as a portable player. I would recommend removing the leather case when it is in DAC mode to improve cooling. Second, the AK240’s volume control is inactive in DAC mode. If you need to attenuate the volume level, you must do so by some other means, such as the software-controlled volume in your player app. (With high-sensitivity in-ear monitors, such as the Westone ES-5, the amount of attenuation required for comfortable listening can be rather severe, which may result in some loss of resolution due to extreme attenuation.)

Third, when using Audirvana Plus with the unit in DAC mode I could “trick” the AK240 into getting stuck in DSD mode. After playing a DSD file in Audirvana Plus and then closing the program and opening another playback app, such as iTunes or Amarra Symphony, I would only hear high-frequency noise, not music, when I tried to play a PCM file. To “re-set” the AK240 to play PCM files, I needed to re-open Audirvana Plus, play a PCM file, and then close Audirvana. After this, iTunes and other apps would play PCM files correctly again.

The AK240 has a special 2.5mm balanced-output connection, which is such a new scheme that few cable manufacturers have off-the-shelf adapters available for it. Like 99% of those early-adopters who have an AK240, I had no adapters either. Given A&K’s usual level of attention to detail I was somewhat surprised that a balanced adapter wasn’t included as a standard accessory, but it was not. By the time you see this review some cable fabricators, including Double Helix and Moon Audio, will have custom-made adapters available.

When used as a player via its single-ended headphone output the AK240 could be paired with a wide variety of headphones. Noise and low-level amplifier hiss weren’t a problem even with the most sensitive in-ears in my possession, the Westone ES-5s. On the other end of the efficiency spectrum, the AK240 had sufficient gain to drive a pair of Beyerdynamic DT-990 600-ohm headphones past satisfying levels into the spectrum of sound I call “really darn loud.” Easy-to-drive headphones such as the Oppo PM-1 sounded dynamically alive and were so well matched to the AK240’s output that I would question whether anyone really needs to use an accessory headphone amplifier with the AK240, at least with the vast majority of headphones.

Obviously one of the AK240’s strengths is its flexibility and portability. But for owners of large music collections who want to access their entire collection on the go, the AK240 remains inadequate, as do all portable music players. With 256GB in permanent storage plus one slot with a current maximum storage-capacity of 128GB, the AK240 has 374GB maximum storage. Most mature music collections are substantially larger than this. To bring your entire collection on a trip or vacation would involve multiple mini-SD cards. Not only does each card take a while to be scanned when inserted, but also as you add more music to your main library you will need find some way to keep your portable music library on SD cards updated and current. This can be a lot of extra work and will also require a systematic way of doing the updating. It’s too bad that Astell&Kern doesn’t have a companion app for the AK240 which can find new music and move it onto your AK240’s spare internal storage or SD cards similar to the HAP music-transfer program that Sony developed for its HAP-Z1ES music player.

What does the AK240 sound like? Like music should sound. When you’re not doing critical A/B comparisons with other players, it’s very easy to get lost in the music coming from the AK240. I’ve been making some recordings during the summer that provided me with a good deal of new high-resolution music for evaluating gear. Unlike in the recent past, when the only way I could listen to my DSD recordings was through PCM conversions, now I can listen to the files at their native rate anywhere.

I loaded my latest recordings of Choro Dos 3, Tarka, Matt Flinner Trio, and Bryan Sutton with Chris Eldridge into the AK240 via the Astell&Kern-supplied Android Transfer program for the Mac OS. It’s basically a drag-and-drop application that makes adding files to the AK240’s internal 256GB storage relatively easy. (The app had a habit of working for a while and then stopping mid-file, after which I needed to disconnect and reconnect the AK240 to USB to get the app to work properly again.)


Once my high-resolution DSD files were loaded into the AK240’s internal storage I could compare them with the same files on my computer. The AK240’s sonics did not change one iota when it went from playing the files stored internally to files stored on the computer. Even though they’re identical bits, they had to travel very different paths to arrive at the AK240’s DAC chip. My inability to hear any differences between the two digital signal paths shows that Astell&Kern’s USB interface is very good. Both had equal levels of information, musicality, and pace.

Most of my latest recordings were made “in the field” in non-traditional performance spaces such as outdoors, in homes, and small public spaces. Invariably I must use in-ear monitors to listen while making the recordings. I used these same in-ear monitors with the AK240 during playback. And while I could not do any comparisons between the AK240 and a live mike feed during the recording sessions, I do feel the AK240 did an excellent job of recreating exactly what I heard in the original session. All the subtle spatial cues on my recording of Bryan Sutton and Chris “Critter” Eldritch playing vintage Martin dreadnaughts in a tent, outdoors, at the RockyGrass Academy came through the AK240 with remarkable fidelity. I could hear the water cascading down the St. Vrain River fifty feet away, as well as children playing in the river far in the distance between songs. Also all the subtle tonal differences between Sutton’s 1942 rosewood-bodied D-28 and Eldridge’s 1937 mahogany-bodied D-18 were as obvious through the AK240 as they were at the original recording session.

During the review period I had several USB-capable DACs to crosscheck with the AK240. I wanted to compare the AK240 with the Wyred 4 Sound DAC-2DSDse, but since the DAC-2DSDse lacks an analog input I couldn’t merely hook up the AK240’s analog output to an analog input and then switch between USB DACs via the Apple MIDI control panel. However, I could do this very thing with the just-arrived Oppo HA-1 DAC/pre/headphone-amp. On high-resolution material (any files greater than 96/24) I couldn’t hear any differences between the two DACs, but on 44.1 and Internet MP3 radio streams I felt the AK240 did have a very slight edge when it came to resolving low-level inner detail.

At the time of this review I had five other portable players in-house for comparison—a 160GB iPod classic, an iPhone, an Astell&Kern AK100, a Colorfly C4, and the Calyx M player. In sound quality the Apple iPod 160 was not competitive with any of the other players. The AK100 and Colorfly C4 were close but not quite equal to the sound quality of the AK240. Only the Calyx M matched the AK240’s sonics. Also all other players lacked the features found in the AK240.

The AK100, which has been solid and completely glitch-free during the year I’ve had it, was as quiet and noise-free as the AK240 with sensitive in-ears, such as the Westone ES-5s. The AK100 also drove high-impedance, low-sensitivity earphones, such as the Beyerdynamic DT-990 600-ohm version, as well as the AK240 did. But the AK240 plays 128X DSD in native format, which the AK100 can’t do. The AK240 has a “bigger” and slightly larger overall soundstage presentation than the AK100. And the AK240 also sounds more in control on dynamic peaks.

The Colorfly C4, while limited in that it can’t play any DSD files, does have a powerful headphone amplifier that remained silent with high-sensitivity in-ears, while also having just enough juice to drive anything I tried with it, including the Audeze LCD-2 Bamboo headphones. I did find that on my own high-res 192/24 recordings the Colorfly had barely enough output to play loudly with the Audeze. Given the radical disparity in looks between the Colorfly’s retro-steam-punk styling and the AK240’s sheer slickness, it’s hard to imagine that someone would be attracted to both physical designs equally. Sonically the differences between the AK240 and the Colorfly on 44.1/16 Red Book files were minor. Harmonically, the Colorfly had a bit of additive warmth compared to the AK240, but the AK240 remained more linear than the Colorfly, which became slightly “overcooked”-sounding when pushing inefficient headphones.

The Calyx M ($999) proved to be the most sonically competitive with the AK240. Both produced excellent sound on anything I threw at them. The Calyx doesn’t have all the capabilities of the AK240—it’s “only” a portable player and a USB DAC, and its internal storage is just 60GB, but it also has a very refined interface and ergonomics. Although blessedly silent with sensitive in-ears, the Calyx M had barely enough gain on my own high-res recordings. I had to push the sliding side-mounted volume control all the way up to max to get enough output. But during A/B comparisons of 44.1/16 as well as high-res 128x DSD music files, I couldn’t reliably tell one player from the other. Both the AK240 and Calyx M had an equal level of control and finesse.

Final Thoughts
I’ll admit I’ve been intentionally hard on the AK240, but given its place at the top of the price-hierarchy in portable players, potential owners would consider me remiss if I glossed over any of the ergonomic or performance areas where it might not be perfect. Of course, perfection is a difficult-to-obtain goal. After 35 years of reviewing audio gear rarely has any audio component been “perfect,” but the AK240 comes far closer to that status than any portable player I’ve used so far.

Whether the AK240 is the best player for you depends on whether you require any or all of its unique features. If you already have a high-quality USB DAC, streaming device, and smartphone that uses Bluetooth for streaming, some of the capabilities of the AK240 will be redundant and perhaps the new Astell&Kern AK120 or AK100II would be better options.

As I said at the start, the pace of new portable player introductions has been phenomenal. And if Astell&Kern and others continue releasing new players at this clip the AK240 will most certainly find itself challenged by something new in the near future. But right now, in Fall 2014, the Astell&Kern AK240 is the best-sounding, most fully featured portable player currently available. If you demand “the best” the AK240 should, inevitably, be at the top of your must-have list.


Supported audio formats: WAV, FLAC, WMA, MP3, OG, APE (Normal, High, Fast), AAC, ALAC, AIFF, DFF, DSF, DSD 64, DSD 128
Sampling rates: 8kHz–192kHz (8/16/24 bits per sample)
Output level: Stereo unbalanced 2.1V rms/ balanced 2.3V rms
Output impedance: 1 ohm
DAC: Two Cirrus Logic CS 4398
Decoding: Support up to 24-bit/192kHz
Input: USB Micro-B input for charging & data transfer (PC & Mac)
Outputs: Phones (3.5mm); optical (3.5mm); balanced (2.5mm, only 4-pole supported)
Wi-Fi: 802.11 b/g/n (2.4GHz)
Bluetooth: v4.0
External memory: micro-SD (128GB max)
Supported OS: Windows XP, Windows 7/8 (32 & 64 bit); Mac OS X 10.7
Dimensions: 2.59″ x 4.21″ x 0.68″
Weight: 6.5 oz. (185g)
Price: $2495

ASTELL&KERN/iRIVER INC. (U.S. Distributor)
39 Peters Canyon Road
Irvine, CA 92606
(949) 336-4540

Associated Equipment
Source Devices: MacPro model 1.1 Intel Xeon 2.66 GHz computer with 16 GB of memory with OS 10.6.7, running iTunes 10.6.3 and Amarra Symphony 3.1 music software, Pure Music 1.89 music software, and Audirana Plus 1.5.12 music software DACS : Astell&Kern AK100, Colorfly C4, Calyx Audio M, Oppo HA-1, Wyred4Sound DAC-2DSD se
Amplifiers: April Music Eximus S-1, Wyred4Sound mAMP, Accuphase P-300
Speakers: ATC SC M7 II, Role Audio Kayak, Aerial Acoustics 5B, Audience Clair Audient 1+1, Velodyne DD+ 10 subwoofer
Cables and Accessories: Wireworld USB cable, Synergistic Research USB cable, AudioQuest Carbon USB cables. PS Audio Quintet, AudioQuest Colorado interconnect, Cardas Clear interconnect, Black Cat speaker cable and Interconnect, and Crystal Cable Piccolo interconnect, Audience Au24SE speaker cable

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