Astell & Kern AK100 Portable Music Player Reviewed

Published On: March 19, 2013
Last Updated on: October 31, 2020
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Astell & Kern AK100 Portable Music Player Reviewed

An audiophile quality portable music player has been desired by many. Now, that player may have arrived in the Astell & Kern AK100 portable music player. Steven Stone investigates in this review.

Astell & Kern AK100 Portable Music Player Reviewed

  • Steven Stone is the former editor of He a longtime audiophile and home theater writer, as well as a musician and recording engineer. Steven has written for publications like Stereophile, as well as,, and The Absolute Sound.
    Steven is plays guitar, mandolin, and Ashbory bass and is a collector of fine musical instruments.

Astell-Kern-AK100-portable-music-player-review-front-and-back-small.jpgAlthough there are scads of portable players on the market, very few support high-resolution music files. And while even iTunes can down-sample, compress and then load what used to be a higher-resolution music file into your iPod or iPhone, listening to down-sampled and compressed MP3 files just isn't as musically satisfying as hearing the full-resolution originals. With the new Astell & Kern AK100 ($699), you can play any high-resolution file, up to 192 kHz 24-bit (except 176 kHz 24-bit from its Toslink input) anywhere and any time into nearly any headphone, DAC, or audio system.

Additional Resources
• Read more media server and portable player reviews from
• Explore more reviews in our Headphone Review section.

Beyond being a high-resolution portable player, the AK100 can serve as a Digital to Analog Converter (DAC) via a Toslink input or a high-resolution music source via a Toslink output. For the audiophile who travels a lot, the AK100 can serve as both a source and a playback device for all the music in the library. This is because, unlike most players with built-in storage, the AK100 also offers removable interchangeable storage options via two micro-SD card slots that each support up to 32 GB cards and some 64 GB cards. This card storage is in addition to the AK100's built-in 32 GB capabilities.

At first glance, the AK100 is a small, simple rectangular box that measures approximately three inches tall by two-and-a-quarter inches wide by half an inch thick. Finished in a semi-gloss satin black with a large, nearly two-inch-square touch screen and a single volume control knob on its side, the AK100 has a solid feel that takes it multiple quality notches above your average digital player or smart phone. I can practically hear it screaming, "I am not a disposable portable device."

The AK100 supports a variety of digital formats and resolutions, including FLAC, WAV, WMA, MPR, OGG, APE, AIFF, ALAC, and APE. Playing time varies depending on the file resolution. For MP3s, playing time is as long as 16 hours, but when playing high-res files, battery life drops to "only" 10 hours.

The AK100 comes with iRiver's Plus 4 software for use with Windows XP, Vista, and Windows 7 computers. This software makes moving music between your computer and the AK100 relatively easy and more intuitive than dragging and dropping files into folders. If you plan to use a lot of 96kHz or 192 kHz music files, transferring them can still be a lengthy process.

The AK100 also supports streaming from supported Bluetooth 3.0 devices, such as an Android or iPhone, when they are within a 20 CM range. When a phone call comes through, the AK100 will automatically disconnect. While the Bluetooth connection will support higher-resolution files, the AK100 instruction books recommends files 48K or lower to insure optimal stability.

Controls on the AK100 consist of a volume knob sticking out of one side, three small buttons on the other controlling play/pause, previous/rewind and next/fast forward, and on the top edge, a small button that functions as a volume lock once it has been activated. All other functions are adjusted via the AK100's touch-screen LCD display. The display contains multiple nested menus that keep a majority of the most often-used controls on the main screen. There is one adjustment, buried four levels down, called the "Volume Lock," which most users will want to activate almost immediately, since without it, there's no way to ensure that the volume (and other controls) won't be accidentally activated while the player sits in your pocket.

Among its features, the AK100 offers five-band equalization that can be accessed from its main playback screen. It offers up to 10 dB plus or minus corrections at 62, 250, 1000, 4000, and 16,000 Hz. The EQ is meant primarily to correct for earphones that need help in some part of the frequency spectrum, but it can also be used to correct for a particular album or track's harmonic issues as well. For purists, the EQ function can be completely bypassed, which will also result in a slightly higher output level. My only criticism of the EQ is that the AK100 lacks any EQ save and store functions, so you can't keep multiple EQ settings, such as one for each headphone you use regularly. Every time you change headphones that require EQ adjustments, you must go into the EQ settings and change each of the five bands manually.

Accessories included with the AK100 include a special USB cable for docking, charging, and transferring files, plus a quick-start guide, warranty info, micro SD card containing five sample high-resolution music files, extra plastic screen and back protectors, and a black cloth bag. The packaging is slick but not overdone, featuring a matte black box that slides into an outer sleeve.

When you turn on the AK100, you'd better not be in a hurry, because from off or sleep mode, it takes twenty seconds for it to wake up and become fully functional. Once awake, the AK100's touch-screen is quite sensitive and very responsive. The screen contains information besides the usual song title, artist's name, play, pause, rewind, and song timing. You'll also see the current time, Bluetooth connection status, battery strength, and access to sub-menus for navigating through your library, options, and even lyrics if they're imbedded in the meta-data.

Read more about the Astell & Kern AK100 on Page 2.
Astell-Kern-AK100-portable-music-player-review-front.jpgIf you are a regular Apple user who's accustomed to the vertical
integration of Mac computers, iTunes, iPods, iPads, and iPhones, the
lack of automatic synching and integration with your music library will
seem primitive. It's not that the AK100 isn't Mac-friendly, because it
does "play nice" with a Mac once tethered via its USB cable. But all the
file functions, such as adding or removing tracks, must be done via
drag and drop. It's best to think of the AK100 as an external drive.

users will find the iRiver 4 software makes adding and subtracting
music files more intuitive and less bare-bones, but even with this
software, managing music for the AK100 will never be as much of a
no-brainer operation as with iTunes/iDevcies' nearly automatic
synchronization. But for anyone familiar with moving files on and off
external drives, the AK100's interface should be easy to use and

One control that you won't find on the AK100 is a
mute button. Instead, when you need to cut off the sound, you must use
the pause control that's located on the touch-screen. If you've
activated the "Volume Lock" button, you will have to push it first
before you can access the touch-screen to use the pause button. While
this is less convenient that just pushing mute, A&K felt the loss in
sound quality caused by a muting circuit was too great to include it in
the AK100's feature set. While some potential users might be turned off
by the AK100's minimalist approach to ergonomics, anyone whose primary
focus is optimum sound quality will appreciate Astell & Kern's
decision to optimize SQ, even if it means fewer ergonomic bells and

The AK100's volume control has a numerical scale from 0
to 75, which relates directly to dB levels and allows for .05 dB
adjustments. I found the range suitable for almost every headphone I
tried with it. The most sensitive in-ear monitor I have, the MEE
Electronics A161P (110 dB sensitivity, 32 ohms impedance), used the 40
dB setting while my Beyer Dynamic DT-990s (600 ohm version) used the
full output of 75 dB to play at a decent volume level.

Some early
adopters have made much of the AK100's 22-ohm output impedance. Red
Wine Audio offers a $250 modification that bypasses the AK100's 22-ohm
resistors and directly wires its output stage to the headphone jack with
Cardas wire. For some headphones, this bypass will improve their
performance, specifically with multi-element in-ear monitors, which can
have complicated crossover impedances and IEMs with very low impedances.
But I didn't find this 22-ohm (or 20, in the specs) impedance to be an
issue with any of the headphones and earbuds I tried with the AK100.

Astell & Kern doesn't make any cases for the AK100 besides the
cloth one that came with the unit. A search on eBay turned up a very
nice leather case for $69
but what I'd love to see is a soft gel case to protect the AK100 from
being dropped, plus supply some friction for pocket use. As it is, the
AK100's finish is so slick it can easily slide out of your pocket. (I
once lost an iPod that way - right into the toilet, splash.)

how does the AK100 sound? In a word, stupendous. With a signal-to-noise
figure slightly in excess of 110 dB, the AK100 ranks as the most
noise-free portable playback device I've heard. Music comes out of a
dead silent background that rivals many of the best desktop and
standalone headphone amplifiers and DACs I've reviewed recently.
Imaging, especially on complex multi-miked studio recordings, was solid
and precise.

I used a wide variety of headphones with the AK100,
including the Etymotic ER-4Ps, Shure SE-215s, MEE Electronics A161P,
HiFiMan RE-272s, Ultimate Ears In Ear Reference Monitors, Grado RS-1s,
Audio Technica ATH-900x, Beyer-Dynamic DT-990s, Beyer-Dynamic DT-880s,
Audeze LCD-2s, B&W P5s, V-Moda M-80s, and Sennheiser HD-600s. With
every can, I was able to find the right volume levels without
experiencing any spurious noise or audible frequency mismatches.

favorite combos were the AK100 with the Etymotic ER-4P in-ears and the
AK100 with the Audeze LCD-2. During portable use, the AK100/Etymotic
combo delivered a remarkably high-resolution and neutral presentation.
At home, the AK100/LCD-2 combo was lushly seductive, without sounding
slow or heavy.

High Points
The AK-100 delivers superlative sound quality in a small form factor.
The AK-100 has support for full-resolution 44.1, as well as 88.1, 96, 176.2, and 192 kHz files.
The AK-100 is compatible with a wide variety of headphones and in-ear monitors.
The overall fit and finish is well above that of most portable playback devices.

Low Points
The AK100 does not come with any software for the Mac, but the Mac OS is supported for basic drag and drop functions.
The AK100's 20-ohm output impedance could present mismatch issues with
some extremely low-impedance, high-sensitivity earphones.

Competition and Comparisons
the AK100 has few, if any, direct competitors. The most popular
playback devices, such as the iPhone 5 and iPod Touch, do not support
high-resolution files. HiFiMan HM-602 ($399) has removable cards for
storage like the AK100, but has a maximum resolution of only 96/16
(96/24 files are down-sampled to 16 bits). At the Rocky Mountain
Audiofest's CANJAM, HiFiMan demonstrated a new model, the HM-901, which
does support higher-resolution files, but it isn't available yet. For
more on these great portable players, please check out Home Theater
Review's Headphone page

Obviously, not everyone needs high-resolution
capabilities in a portable music player. But if you do want to be able
to take full-resolution uncompressed music wherever you go, the AK100
delivers. While its ergonomics may not be as slick as an Apple iPod, the
Astell & Kern AK100 is easy to use once you learn its
idiosyncrasies. And when it comes to pure unadulterated sound quality,
the AK100 leaves the iPod, iPhone, iPad, and all their imitators in the
dust. Sure, it's not inexpensive, but for anyone who demands the best
sound quality currently available in a portable playback device, the
AK100 is the device to own.

Additional Resources
Read more media server and portable player reviews from
Explore more reviews in our Headphone Review section.

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