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August 2015
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Astell&Kern AK Jr Portable MQS System
The lil' DAP / DAC that could. Big 'n' beautiful sound in a small package.
Review By Steven R. Rochlin

Astell&Kern AK Jr Portable MQS System

 There is no doubt Astell&Kern has been one of, if not the leader, of portable digital audio players (DAPs) in recent years. While their products have always started at over $1000, with their new top-of-the-line AK380 (reviewed) coming in at $3500, today they are playing the other side of price extremes. From the eye-poppingly priced AK380 reviewed earlier, this review concerns Astell&Kern's new $499 AK Jr. We all know technology always gets better, cheaper, and smaller. Thinking back to the old Osborne 'transportable' computer during the early 1980s, it had only 64 kb of memory, a built-in 5.25" monochrome screen and 1200 baud modem. The Osborne was a technological masterpiece at the time and weighed a hefty mere 23.5 lbs. To put this into perspective, your cell phone has about the same size color touchscreen, a massive improvement in processing power and gargantuan memory storage capability by comparison. In addition, today we have Internet speeds in the Mbs.

Astell&Kern's AK Jr greatly benefits from many years of extensive research and continual development. Over time, technology trickles down and today the AK Jr is the company's entry-level digital audio player that builds upon everything Astell&Kern has learned over the years. It has a bright 3.1" 240 x 400 pixel resolution LCD touchscreen that is said to be about 1.4 times larger than their original AK100 produces a few years back. AK's lil Jr is also thinner, lighter and handles all the usual digital file types including lossy MP3, lossless FLAC and Sony proprietary DSD. DSD (direct stream digital) is converted to PCM (pulse code modulation) so it is not handled natively for you pesky sticklers out there. If implemented correctly, which is not that hard to do nowadays, DSD (DFF) to PCM is fine by me. It is how the unit sounds, not what it can and can't do natively, that matters.

Internally, Astell&Kern's AK Jr uses the Wolfson WM8740 DAC chip. While the higher end models by the company use two or more DACs for balanced processing, within this elegant and slim design they choose a great sounding single chip solution. There is no dispute by audiophiles and portable audio enthusiasts alike that Wolfson has been producing excellent sounding DACs for many years. Bluetooth version 4.0 provides a wireless connection, yet with some loss of sound quality of course because that is the nature of the Bluetooth beast. There is no Wi-Fi and thus you can't access music within, for example, your NAS drive or cloud storage. Fortunately, Astell&Kern's AK Jr comes with 64GB of memory internally and has a slot just above the right side volume knob for a microSD card. You can easily insert upwards of a 200GB card to expand music storage capability. Of course you can carry multiple microSD cards and swap them. I'm waiting for the 512GB microSD card ($1000!) to come down in price since 128GB cards are getting to be pretty cheap today, and will be cheaper tomorrow, and throw-aways in a decade. Well, it is better than when I paid $80 for an 8MB memory card (not a typo, it was indeed $10 per MB) for my digital camera years ago. So see, technology gets better and cheaper over time.

With a relatively healthy built-in stereo amplifier, the AK Jr has a maximum output level of 1.95 Vrms at a low impedance of 2 Ohms. All of my CIEMs including the UE 18 Pro, Noble Kaiser 10, and both JH Audio's JH-13 and Roxanne were easily able to reach ear-bleeding volume levels. The OPPO HA-2 also reached satisfyingly high output volume. This includes using my typical car audio 'basshead' tracks, since deep bass notes are the most power hungry frequencies within the audio spectrum to reproduce acoustically. Unlike lesser devices such as your cell phone, you have an abundant 152(!) steps of volume control via the touchscreen or the right side volume control. Turning the round dial one click moves the volume in 0.5dB increments and a finger flick gets you about 6 clicks. When the touchscreen is on, you can drag your finger to the right to turn down or left to turn up the volume level at a faster rate than the right side hardware control.

Even with the OPPO HA-2 at full volume output I could not detect any dynamic compression, which can happen when an amplifier circuitry runs out of reserves. Speaking of audio output, you can also go into the Settings menu and choose Line Output to change from headphone to Line Out. This is great when you want to use the unit in your car, a home stereo system, etc. As longtime readers know, portable audio players always find their way into my car audio system via Kimber Kable's superb GQ MINI-Ag 100% silver connector.

Another great feature of the Astell&Kern AK Jr is the ability to be used as a 24-bit/96kHz external DAC for your computer. It is easy to hook a standard USB to micro USB cable, included with the Jr, from your computer to the AK Jr. Then press the touchscreen choice Connect To USB DAC and CAH-CHING you're in external DAC mode so that the sound from your computer comes through the AK Jr. Also, when you hookup the USB cable to your computer the touchscreen also allows you to choose between just charging the battery or connect as a removable disc. Connecting as a removable disc allows you to transfer files from your computer to the AK Jr's memory.

Astell&Kern AK Jr Portable MQS System

With a slim and elegant design measuring a mere 2.08" x 4.60" x 0.35" (WxHxD) and weighting a paltry 3.45 ounces, it is extremely easy to put the AK Jr within your pocket without feeling like you have an ass wart or carrying a brick. While lightweight, the unit feels very solid and built for action. The aluminum body has slightly curved edge sections and looks great without a 'Hey look at me" shout-out like other players. For the paranoid types out there, you do get a few screen protectors in the box, plus a USB cable and manual. Astell&Kern's AK Jr does not come with a case or ear buds, yet you can order some great cases right now from Analogue Seduction online in a wide variety of colors and styles for around $40. Astell& Kern has cases available in six different colors for $50.


Astell&Kern AK Jr Sound Quality
Naturally I was eager to get the AK Jr for review so I could spend some quality time with this little jewel. Packaged neatly within its box, I was quick to unwrap it, put in my specially-prep'ed 64GB microSD for reviewing DAPs and press the power button. Being that the Astell&Kern AK Jr is unbalanced, a special high quality adapter allowed me to use the balanced Double Helix Symbiote SP 8 silver cable on my fave Noble Kaiser 10 CIEMs and off I went. After a handful of songs with the unit freshly out of the box it reminded me of the way Sony's NWZ-A17SLV player sounds, and that's not a good thing folks. A bit bright, lacking in dynamic expression with a good quantity of gradients, and was just a bit rough around the audio edges. (Sigh) Ok, well, this is 'cold out of the box' so let her burn in. A few taps on the touchscreen and she was set to repeat all songs. After three days of continuous playing both on and off USB power I gave it another listen and it was sounding better. After 200 hours of playing it was time to sit down and give the AK Jr a serious listen. During break-in I did test the battery life a few times with mixed audio media (MP3, FLAC and DSD/DFF) and the internal non-removable 1450mAh 3.7V Li-Polymer battery seems to last around 10 or so hours with the screen off. With my usual set of lossless FLAC, DFF and yes lossy MP3 files because not everyone uses lossless 100% of the time, it is now time to rock this lil puppy.

Quiet. Even with the efficient Noble Kaiser 10 there was zero hiss or background noise. Nada, none, zilch! When changing tracks there was nary a click, pop or extraneous noise. It was pure music, and here is where I'm starting off by saying that 'jump at you' dynamics were impressive for such a tiny and inexpensive device. Obviously Astell&Kern put quite a bit of effort within the Jr's analog output stage. Since we're on dynamics, micro dynamics are very good and big audio pyrotechnics are most impressive. Whilst not the best I've heard at any price, and remember I've played with the $3500 AK380, have the $2500 AK240, $1200 Sony NW-ZX2 and many others here, for $499 I was hearing far more dynamic shading with oomph and power than was expected. At this price range, engineering 'corners' need to be cut. Yet when it comes to the important amplification section within this lil AK Jr am hard-pressed to say much of a cost-savings was involved other than the Jr being unbalanced versus the additional costs for supporting circuitry and DACs needed for balanced output.

Astell&Kern AK Jr Portable MQS System

I used the impressive JH Audio Roxanne with stock cables (waiting on the Double Helix silver version) and accurate Ultimate Ears 18 Pro custom plus my fave of the bunch Noble Kaiser 10 to really get a good feel here of this DAP. Astell&Kern's Jr is neutral to a small teeny tiny touch of warmth. DAPs like the Sony NW-ZX2 produce a richer harmonic tapestry, which can be a good thing for cheap and cheesy universal ear buds / IEMs and certain bargain-priced headphones. Speaking of headphones, of course the OPPO HA-2 were put through the paces and with the AK Jr it solidified my highly positive review of these headphones. Getting to the down 'n' dirty of it, harmonically Astell&Kern struck an excellent balance of accuracy without the music being strident or annoying. In fact there were times music was more enjoyable over the AK Jr versus the over twice as expensive Sony NW-ZX2. The $499 AK Jr crushes the $300 Sony NWZ-A17SLV when it comes to a low-priced unit you can listen to hour after hour imho.

For you PRATaholics, here again we once again find ourselves in the neutral, balanced, to slightly groove side of things. PRAT, for those unfamiliar, is Pace, Rhythm And Timing. Call it groove or funk factor if that helps ya. Furthermore, and I'm kinda jumping ahead a bit here within this review, as the superb inner resolution and dynamic shadings play extremely well together to produce PRAT at this price level. It is those very critical subtle-yet-audible timing cues playing their part of the music's whole. Ok, guess it is time for me to write about the Astell&Kern Jr's resolution.

Color me impressed! For half a kilobuck you get a remarkable amount of resolution. This is no doubt in part to their choice in DACs, and the Wolfson is highly desirable by audiophiles and music lovers alike for good reason. When combined with the very fast and clean amplification section within the Astell&Kern AK Jr, I feel you are getting around 90% or more of those top players for about one-fourth the price. Almost want to say 95%, yet am waiting for the AK380 to arrive here, which after multiple listening sessions at shows sounds to be the new reference unit in achieving the ultimate in portable music playback. In addition, the whole scale of what is possible at a given price point is moving higher with each passing year, no make that month, as new DAPs become available. Ah yes, this is one of the many difficulties, pitfalls if you will, of being a longtime high fidelity audio reviewer. What we felt was reference-level three years ago are now normal for mid-priced products.

Overall resolution is remarkable. It does an inspiring job at unraveling intricate passages yet keeping their independent volume and stereo image within the textural seams of the music intact. It is not up there with the AK380 or to some extent the Sony NW-ZX2, yet far better than I recall with the lower priced Sony NWZ-A17SLV and, dare I say this, perhaps better than my original AK120 (read: not the newer II version, which is not in-house for testing/comparo). You get an excellent dose of resolution and hints of what you can expect within Astell&Kern's higher priced offerings like the AK240 and reference-grade AK380. Seen below is a size comparison of all Astell&Kern digital audio players, with the AK Jr being to the far left.

For you bassheads, there is a good amount of drive and power behind the deepest of bass notes. It is not bedrock solid like the AK380, and not augmented like the Sony NW-ZX2 when you use the Clear Bass equalizer setting, yet you get resolution and cleanliness over low frequency pyrotechnics. Astell&Kern's AK Jr resolved my basshead car audio FLAC tracks during those Miami Bass Wars days, yet does lack that last 15% or so of solidity as the sound 'drops off' a bit below 40 Hz. It is a slow roll-off to my ears, yet I'd prefer this over more bass yet with distortion. Yes you can still hear the deep bass, yet it seems to lack that last bit of torque 'n' grunt to pull things through at full force. So it's there and relatively accurate, just not fully amplified by a nearly endless foundation as I recall with the $3500 AK380. Compromises at $499 had to be made and, glad, they kept it on the side of accuracy versus throwing more, usually flabby and bloated, bass at your ears. Please keep in mind I'm talking about the very deepest of bass that most songs have zero of. It is a type of torture test, frankly, as I feel a reviewer must take everything into account to fully test a product at all extremes.

High frequency extension is smooth and clean, yet not the last word in stratospherically delivered. Drum cymbals, bells and upper reverb within recordings have far more delicacy than I was expecting from a player at this price level quite frankly. Midrange is also outstanding and well-balanced within the overall musical presentation. Yeah, I keep saying a balanced sound, yet it is the word that keeps sticking within my head. Goldilocks would love the AK Jr because everything from the price / performance is just right to my ears. There is no doubt in my mind the AK Jr is a lil overachiever; sounding far better than expected in many ways. Ok, so neither are reference level, yet you get so very much for $499 it makes me reconsider the laws of diminishing returns. Perhaps chalk this up to trickle-down technology combined with Astell&Kern's many years of experience and know-how.


Notes Between The Notes And Some Car Audio Tunes
Here is where we get to the nitty gritty and comparo with the over twice as expensive $1200 Sony NW-ZX2. The $499 AK Jr has excellent speed and so the sound you hear, or shall we say don't hear, between the notes is excellent. Unlike the Sony, which we'll get to in a sec, the AK Jr simply presents the music whereas the Sony does do a bit of DSP trickery to give you a bit 'more'. Look, I love DSP when it is implemented properly and complimentary to the music, and the more I listen to the Sony NW-ZX2 the more I'm convinced there is some DSP processing trickery going on. Ok, all DAPs have digital processing, as that's how it turns digital signals to the analog sound we hear, yet codecs and other digital processing can greatly affect the way a device under test sounds. Even lowly MP3 seem to have this glorious upper frequency extension with the Sony NW-ZX2, yet is absent with the same track on the AK Jr. Also, while the soundstage is very good on the AK Jr, the Sony is doing something to really bring out this sumptuously enveloping soundscape. Microdynamics are indeed better with the Sony NW-ZX2 as are the way notes fade-away plus subtle volume changes within said instrument(s) is delivered to the listener. There are more volume shadings with the Sony than the Astell&Kern unit. Which brings us to...

Astell&Kern AK Jr Portable MQS System

Within my high-end car audio system the Sony's DSP and soundscape was more evident than with headphones and CIEMs. In addition, the Sony's Clear Bass combined with Sony's DSP gave the car a more involving experience (for me). Darude's song "Sandstorm" is a classic and with the Sony I feel like the car is a rolling dance club, whereas with the AK Jr it has an audible flavor closer to that of a recording studio. No doubt the Sony's overall DSP combined with their Clear Bass equalization, which helps to synthesize bass notes, is more like a dance club. With jazz and classical music this effect is less so with the Sony and thus closer to how the AK Jr sounds, yet with what I'll call TiŽsto... Say the following words out loud when you read it: Boots-n-pants -n- boots-n-pants -n- boots-n-pants -n- music... the Sony is more enjoyable in the car. I wanted to love the AK Jr playing through the car audio system, yet couldn't quite get there with dance, dubstep and the like. This is most definitely a personal preference and choice of music style. With classical, jazz and rock music there was less of a decisive preference of one portable music player over another. The really big difference is phasing and soundscape in the car, as the Sony just sounds ever so more enveloping whereas the AK Jr is like your typical German high-end automotive system versus, say, one that is British. Car audio and general automotive reviewers agree that the British sound systems are better than their German equivalent and I'm not one to disagree here.


So where did Astell&Kern cut corners to reach a $499 price tag? Ahhh, great question! Even with a measured 120dB crosstalk specification, the Astell&Kern AK Jr does have a slight lacking in the ultimate of soundscape definition. What I mean by this is that some of the pinpoint imaging, and at times a slightly wider image within the soundscape, is not as precisely defined within the matrix of the music. This is also, perhaps, one of the advantages of using balanced amplification and balanced IEM / headphone cables. General soundscape width and depth is very good, so this diminishing is not necessarily holistic more than it is within the threads of the music's fabric and taken on an absolute level with cost-no-object products. For photographers, think of it like a lens that has a slightly lower DxO score in sharpness, and yet rates well with a low optical distortion and low vignetting. Thus it is mainly in the visual image's resolution of specific items as portrayed within the photograph as a whole. The reason i'm trying to be very careful with words is that the music resolution is quite good, it is the instrument's imaging, shape and sizing within the music as a whole that lacks the best-of-breed in focus and clearly defined edges. Instrument imaging is not wildly smeared, it simply lacks that last bit of in-focus sharpness of the instrument's audible edges within the fabric of the soundscape.

Astell&Kern AK Jr Portable MQS System

Another situation pointed out by those who already have the unit is the stuttering and hiccupping of the graphical user interface (GUI). While I'm sure a firmware update can solve this issue, it does need to be said that with firmware 1.02 there are times the unit is slow to respond to your finger touch when scrolling, etc. In fact on my test microSD card for review/torture testing there are folders with quite a few 'mixed media' songs that include FLAC, WAV and DFF files. Yesterday, the Astell&Kern AK Jr came to a virtual halt-stutter-halt whilst I was trying to access a specific song within a folder. Am sure a firmware update can easily solver this, so we're all just going to have to wait for the solution. In fact I was holding off publishing this review for a week or so in hopes new firmware would be released. Another problem that crops up is the sensitivity of adjusting the volume level on the touchscreen, as it is easy to go from low to full with a finger slide/move for someone like me. Thus be very, very careful and move your finger s-l-o-w-l-y and in very small amounts across the touchscreen or you'll find yourself being at near zero or near full volume before you know it.


If we're talking generalizations, which is exactly what a conclusion generally is, my feeling are a preference towards the Astell&Kern $499 AK Jr over the original $1299 AK120 reviewed in August 2013 and that, in itself, says quite a bit about how good this little Jr reproduces music! The compromises made are right in line with exactly what I'd prefer. Keep the musical harmonics to the slightly nice versus sterile side of life, add in a touch of impressive resolution and deliver a nice dose of soundscape. Give up a bit by eliminating the additional costs of dual DAC chips and the inherent advantages of balanced amplification. In fact I keep going back to the $499 Jr as a more transparent player for inexpensive reference even over the $1200 Sony NW-ZX2! Now before anyone gets carried away, the rich harmonics of the NW-ZX2 and the way it handles microdynamics are ahead of the AK Jr, yet it is those audible leanings towards pleasant and known colorations including deep bass 'effects' that bring a bit of additional 'life' to music I tend to play in the car and, at times, home. If you love classical, jazz, rock, etc and are on a tight budget, the AK Jr just might be that more neutral sound you are looking for. It is a personal preference of what the listener desires given the task at hand plus the mating IEMs / headphones. If I want accuracy, then the Astell&Kern AK Jr is closer to reality than the Sony. It is akin to in-ear monitors where some prefer one over another. Neither is perfect, yet one may be more to your preference whereas another might be more towards someone else's desires. For a mere $499 you get an extremely compact, very clever player with good battery life. In my eyes, and ears, Astell&Kern's AK Jr is the low-price leader for sound and build quality. As much as I physically pressured the casing in many ways, it withstood quite a bit of this torture test too.

Of course what really matter is if the music is enjoyable, and here we have a winner! There's always a delicate balance between extreme accuracy and musicality. It is not that they are mutually exclusive, yet at this lowish price level it becomes far more challenging. Astell&Kern has done an excellent job with the AK Jr. This extremely lightweight and small DAP allows you to bring great audio anywhere, anytime, and will deliver many hours of musical delight. I keep looking at this tiny player and admiring how big it sounds, with plenty of output for all my CIEMs and the OPPO HA-2 headphones. Big, beautiful sound within such a small package that I never felt was possible. Bravo Astell&Kern, you've got another winner on your hands! As always in the end what really matters is that you...


Enjoy the Music,

Steven R. Rochlin



Sub-bass (10Hz - 60Hz)

Mid-bass (80Hz - 200Hz)

Midrange (200Hz - 3,000Hz)

High Frequencies (3,000Hz On Up)



Inner Resolution


Fit And Finish

Self Noise

Value For The Money


Type: Portable media player / DAC
Frequency Response: 10 Hz to 70 kHz 
Signal To Noise ratio: 112dB
Stereo Crosstalk: 120dB
THD + Noise: 0.005%
Clock Jitter: 50ps
Internal Storage: 64GB NAND flash
Expansion Slot: One microSD card slot
Battery Power: ~7 hours for DSD and 24-bit/192kHz FLAC, 12 hours with mixed media 
Sampling Rate: 8 to 192 kHz and DSD64 (1-bit 2.8MHz) 
Equalizer Function: User adjustable at 62 Hz, 250 Hz, 1 kHz, 4 kHz, 16 kHz plus fixed Pro EQ 
Gapless Playback: WAV, FLAC, AIFF, and ALAC 
DAC: One Wolfson WM8740 
Input Terminal: USB micro B for charging, data transfer and use as an external DAC
USB DAC Function: Up to 24-bit / 96kHz 
Analog Output Jack: 3.5mm stereo
Maximum Output Level: 1.95Vrms per channel
Output Impedance: 2 Ohms
Physical Buttons: Power-screen on / off, rewind, play / pause, fast-forward, and dial volume
Volume Control: 152 steps
Bluetooth: Version 4.0 A2DP and AVRCP
Display Language: Japanese, English, Korean, Chinese, Russian, Spanish, French, German, Italian, and Thai 
Internal Power Supply: 1450mAh @ 3.7V Li-Polymer
Touchscreen Display: 3.1" TFT color LCD WQVGA 240 x 400 pixels 
Size: 2.08" x 4.60" x 0.35" (WxHxD)
Weight: 98 grams 
Included Accessories: microUSB cable, screen and rear protective sheet.
Price: $499


Company Information
iriver House / Astell&Kern
902-5 Bangbae-Dong
Seoul, Korea

Voice: +82-2-3019-1700
E-mail: webmaster@iriver.com
Website: www.iriver.com


39 Peters Canyon Rd.
Irvine, CA 92606

Voice: (949) 336-4540
Fax: (949) 336-4536
E-mail: support.inc@iriver.com
Website: www.AstellnKern.com













































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