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Astell&Kern AK100 portable player
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Sound Quality
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Astell&Kern AK100



Able to play top rate digital files, the Astell&Kern AK100 is a portable player with a difference, Noel Keywood finds.


This tiny music player fitted my shirt’s top pocket, making for a short connection to a pair of headphones I could barely take off. The reason being it offers top digital quality, far better than CD or most other players on the market. The Astell&Kern AK100 is a high definition portable audio  player – think iPod – of super high quality. Although a portable to make others weep, it can also drive a hi-fi system – it’s been designed to do so – providing better sound quality than CD.
    Measuring just 80mm high, 65mm wide including the protruding volume control button, and 15mm deep, the AK100 is one small player. It plays music stored on 32GB of internal memory or from two micro-SD cards that can be inserted into slots in the player’s base, behind a small sliding door. At around 100MB per 24/96 track that amounts to ten tracks per GB, so a 32GB card (£18 or so) will hold around 320 songs, meaning the player can tote around 1000 songs maximum, using two 32GB cards in addition to its own memory. That’s plenty enough for most people.

   The AK100 is basically a portable music player with a single 3.5mm headphone socket. Controls are few. There is a big rotary volume control at right, pause/play and forward and backward skip buttons at left, plus an on/off button on top. The buttons are small and sit almost flush. The combination headphone socket contains an optical S/PDIF digital output for connection to an external hi-fi digital-to-analogue convertor. You need an adaptor to plug in an optical cable, but many leads come with them as standard. Unusually, there’s an optical input too, so the player can be used as a DAC, but it cannot record through this input.
    On the base is a micro USB port for connection to a computer and to charge the internal battery; the importers tell me that audio is available through this connection too. It takes around 5 hours to accept a full charge and the battery is not removable, so you cannot carry spares. A USB socket able to deliver enough current to support charging is needed, which usually counts out keyboard outlets and such like. Our player was reluctant to charge fully overnight on a computer hub outlet, but charged fast from an iPhone charging unit (£15). A small battery indicator icon turns from red to white when charged, but shows nothing in-between, unlike most battery indicators. After some use to cycle the battery we recorded 8hours 20mins continuous playing time, playing one song on repeat, with display off, but the importers claim 10hours and Astell&Kern 16hours. The discrepancy may be explained by variability between batteries, since the chemistry of small Lithium Ion batteries is unpredictable.
    The instructions, which you can download from, mention little of this, which wasn’t helpful, and they failed to mention many peculiarities, such as the player being switched on before it can be recognised by a computer.
        The front carries a bright touch screen that needs a quick stab to work, or it remains unresponsive. Stab it whilst playing, to move from full colour cover artwork to play controls, pause/play, skip forward or back. These duplicate the function of the play buttons, so there are two control options. There is no external remote control option in a headphone lead extension, so you have to reach into your pocket to start, stop or adjust volume.
    There is, however, a Bluetooth short range radio transmitter that enables wireless connection to the hi-fi if you have a Bluetooth receiver, but Bluetooth works at CD quality (16bit) compressed to reduce data rate. High resolution 24bit files will play but their quality isn’t maintained. Degradation from 24bit to 16bit, through word truncation, is not drastically obvious, but there is an appreciable difference between the two: 24bit is smoother, has more low level detail and sounds less ‘barren’. Bluetooth connection is a convenience; the optical S/PDIF output supports full 24/192 quality measurement showed.
    The AK100 is one of few portable players available able to play top resolution 24bit/192kHz sample rate files through its internal Wolfson DAC. Generally, 24/96 is plenty enough resolution for headphones of good quality, the advantages of 192kHz are hardly audible, but file sizes are double those for 96kHz sample rate: think 200MB or so. But some may want 24/192 when driving a top quality hi-fi system. Whatever the practical issues, the time is approaching when 24/192 is a must, simply because the hardware exists and companies like iriver are using it.
    An on-screen display flags up bit depth and data rate in small orange text, and the player also makes all high resolution music files available through a folder labelled Mastering Quality Sound, which strikes me as a nod to Apple’s requirement that studios provide 24/96 Masters for iTunes, even though Apple do not, as yet, offer such quality. The days when studios are able to provide pristine studio masters direct to listeners are here though, it’s just that the world has to catch up and the AK100 is part of this process.
    The AK100 plays WAV, FLAC, WMA, Ogg and MP3 music files now, and all future AK100s will also be loaded with Apple AAC, ALAC and AIFF files, Astell&Kern tell us, these being downloadable from the iRiver web site for older AK100 units.
    The sheer quality of the AK100’s replay circuits, from its high quality Wolfson DAC, to its unusual headphone amplifier appreciably improved sound quality I found, even from MP3s and the like; this player does improve on other portables. The reason is simple, substantial and significant: the AK100 is more a ‘CD player’ than a portable. Where portables always use cheap low quality DACs and weedy headphone amps that deliver 0.3V, the AK100 has a top quality Wolfson DAC on board and delivers no less than 1.55V from its headphone socket, little less than a CD player. And you can hear this, not just as greater volume but as vast dynamic range. Headphone amps are constrained by hiss at low levels and by distortion at high levels, and they are all the same, because group-think and aural safety make them that way. I was quickly aware, before I measured the AK100, that it doesn’t have the usual noisy headphone amp and the shaky quality they possess – more of which soon.




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