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Astell&Kern AK120 portable player
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Uprated line amplifiers put the new Astell&Kern AK120 portable music player ahead of the field. Noel Keywood has the numbers.

Back in our March 2013 issue I was stunned by the quality of the Astell&Kern AK100 portable music player. It plays the highest quality digital formats available and has a headphone output with sound quality that blows others away. Now, iRiver (Korea), makers of this player, have released a 'better' model, the new AK120 reviewed here. I was a bit puzzled by this, since there wasn’t so much you could do to the AK100 to improve it.

    Having measured the new AK120 thoroughly, I see what iRiver have on their mind. The company is technology driven; no one puts top Wolfson DACs into a portable player – but this player has them. They are serious audiophile items.

    If you want to inhabit top-end territory, you have to pay attention to the numbers. The only valuable F1 car is the one at front and it’s lead can be slender. I said in our original review the AK100 “approaches the limits of what’s possible”, so whilst being way better than any other portable it still wasn’t technologically in front of the best stand-alone hi-fi DACs. Well, the AK120 has been devised to run at the front – and that’s why at £1140 it is double the price of the AK100.
    In the AK120 iRiver have come up with a digital player able to deliver the very best from high resolution digital music. This is a serious audiophile device that can be used both as a portable and a digital player good enough to feed a top quality hi-fi system: think of it as a high resolution CD player and you start to get where iRiver are coming from.

   As audiophile CD players go, the AK120 is not expensive, yet it plays digital files right up to 24/192 quality,  where CD is limited to 16/44.1 –  the best possible in the early 1980s. So where the AK100 is a great quality portable, the new AK120 is a top digital player that is also portable – and it sounds way better than CD. But then, since it arrived 30 years later perhaps we shouldn’t be surprised.
    To lift quality further, new output stages have been used, to better complement the twin mono Wolfson DACs. As a result the AK120 is slightly larger than the ‘100, measuring 89mm high, 60mm wide and 15mm deep. Height has grown by 10mm, the 100 being 79mm high. Note that the width value is that of the case only, it does not include the volume knob that adds another 5mm. That still makes the AK120 easily pocketable and at 126gms it feels weighty but isn’t actually heavy.
    On board is a 2000 mAh Lithium Polymer 3.7V re-chargeable battery to keep the player boogying for up to 16 hours, iRiver claim, and I recorded 14.5 hours on repeat play.


    Music can be stored on 32GBs of internal memory, or on two 32GB MicroSD cards that plug into a slot in the base of the player, totalling a massive 96GBs of memory in all. That’s roughly 145 CDs, but as 24/96 hi-res files are four times larger, that figure drops to 36 CDs, unless they are FLAC (losslessly compressed), in which case it jumps up to 72CDs, or 720 tracks storage capacity in 24/96 FLAC.  Whatever, there’s enough memory to store a lot of music in high resolution form and it’s a doddle to pre-load MicroSD cards by plugging them into a computer’s USB port, using an adaptor. The cards are so small – fingernail size – that a matchbox full would store tens of thousands of tracks; a 32GB card costs around £15 at present.

    The AK120 will play WAV, FLAC, WMA, MP3, AAC, ALAC, AIFF, OGG, ASF and APE files. I played AIFF and AAC from Apple iTunes, plus WAV and FLAC up to 24/192 resolution, without problem, including through the optical connectors; there are no limitations here (some optical outputs work to 96k only).  iRiver say DSD files – found on SACD discs – can be played too. However, I tried DSD64 and 128 with the DFF extension, and a DSF file, and none would play; we were then told this was a future upgrade.
    I found the AK100 a little awkward to use but acclimatised to it. So I was pre-conditioned for the AK120. It has a small, colour touch screen of good resolution and I now realise I have hardly ever used the operating buttons. The player can be operated by touching the screen, but when it’s in your pocket you’ll be needing the buttons. It cannot operate from a remote control in a headphone lead.
    The small black case looks featureless, but it disguises many inputs and outputs, and a lot of associated functionality. One of the small 3.5mm jack sockets on its top face accepts headphones, just like any other portable but – like Apple – iRiver fit a dual-role connector: it also acts as a digital output, using an optical S/PDIF cable fitted with an adaptor. This can feed an external DAC or digital amplifier.
    Similarly, the analogue signal from the headphone output can also feed a hi-fi amplifier, because it uses line drivers, rather than the usual noisy headphone amplifier of other portables. To do this either a 3.5mm-to-phono plug adaptor cable is needed, or a 3.5mm plug-to-phono socket adaptor, budget versions of which can be found in Maplins, in the UK.

    The AK120 delivers no less than 1.6V from its headphone output, close to the 2V figure of a CD player, and way higher than the 0.3V of most portables. It is here also that the AK120 reveals its advantage over the AK100, measurement showing a massive 115dB dynamic range, against 110dB for the AK100. This is very good from 24bit digital and rarely bettered. That’s 15dB better than CD, by the way, and 22dB better than other portables – and you can hear this, more of which later.
    A second ‘headphone socket’ is in fact a digital optical input, allowing the AK120 to be used as a high quality, battery powered DAC.
    On the bottom face sits a Micro USB B input that is used for charging and for data transfer from a computer, both Mac and PC being compatible without special software.
    And finally it also has a Bluetooth short range radio link on board. If your system has a Bluetooth receiver, this is a convenient wireless connection, but at present aptX streams at CD quality, compressed 5:1 to reduce data rate, so quality isn’t maintained.


With both Philips Fidelio X1s and my small Jays V-Jays travelling 'phones, the AK120 went appreciably louder than any other player, like the AK100 before it, but the Philips 'phones were insensitive and I found myself up to 65 (75Max) on the volume control, which surprised me. Most players would struggle to drive the Philips loud so I was grateful for the grunt of this player.
     Like the AK100 the AK120 sounded silky smooth and silences were chocolate dark. As before I found myself cranking volume up with clean tracks like Diana Krall’s ‘Narrow Daylight’ (24/96). Piano sounded gorgeously large centre stage and a plucked acoustic bass provided a firm under-pinning to this track. Ms Krall had a close, breathy presence, on both 'phones and Martin Logan Electromotion loudspeakers.
    The player images with slick precision, due to its low jitter.
    Put all this together with the lovely cleanliness of 24bit and the sonic result is fabulous precision, without that clinical sterility of so much digital. This makes everything so much more enjoyable and accessible. The soaring Hammond organ at the start of Tom Petty’s ‘Refugee” (24/96) swirled through my lounge and the drum kit delivered a firm thump through the Electromotions: this is Rock wrought large and the AK120 delivered it with an easily enjoyed gusto. Detail was unforced but abundant, and dynamics obvious; I fancy this player has slightly better bass strength and definition through its upgraded output amplifiers, against the AK100. My attention was repeatedly drawn to percussion, like a solo drum exercising one bass bin on Roberta Flack’s “Killing Me Softly” (24/192).  Yes, this is an analogue recording from 1973; I also played Otis Redding’s ‘Dock of the Bay’ (24/192) from 1967 and both transcriptions were captivating, delicious insight into the original analogue master making both songs come across as raw and moving.
    Classical music arguably fares better with a player like this. With the Minnesota Orchestra’s rendition of Rimsky-Korsakov’s ‘Dance of the Tumblers’ the orchestra had a scale and might that was convincing, the canvas large and spacious. Horns had a deep fruity quality, strings were lush and smooth as silk – no screech from this player (assuming a good original 24bit recording of course). Switching from 24bit originals to 16bit CD rips on this player made obvious the screech of CD.


Like the AK100, the new tuned-up AK120 is a player that shows what we are moving to: it’s a glimpse of the future. Superb high resolution digital sound quality brings even old analogue recordings to life – fabulous. Its improved output amplifiers strengthen bass grunt when using the analogue headphone output to feed a stereo amplifier, making this a serious digital player, not just a fabulous sounding portable.  Hopefully DSD will work well when it arrives as it is attracting interest, but even without it, the AK120 is a must-have.

A top portable music player with fantastic sound quality. Little comes close.

- plays top 24/192 digital
- can drive a hi-fi system
- small

- no charger
- poor charge display
- no DSD (yet)


Astell&Kern AK120 - £1140

Air Audio Distribution (UK)

01491 629 629

Rohde & Schwarz UPV

Rohde & Schwarz UPV  – the world's most advanced audo analyser.


Like the AK100 tested in our March13 issue, the headphone output of this player delivers very high output of 1.6V, close to the 2V from a CD player and much higher (+14dB) than the usual 0.3V of a typical portable player.
    The DAC and output amplifier were even quieter than the AK100, noise measuring -115dB with a notched out -60dB tone (24bit), to avoid output muting. This raised EIAJ Dynamic Range to 115dB with 24bit, making the AK120 comparable to the best stand-alone DACs. The headphone output is in effect a high quality analogue line output and can be used as one.
    Frequency response was flat from 4Hz to 73kHz (-1dB) using a 192kHz sample rate signal, as the analysis from our Rohde & Schwarz UPV analyser shows, so here again the headphone output performs as well as a quality DAC, maintaining the full analogue bandwidth of 192k sample rate digital.
    Distortion at -60dB was low with 16bit, measuring 0.18% and very low with 24bit at 0.04%, as our distortion analysis shows. This result and low noise both contributed to the player’s high EIAJ Dynamic Range figures.
    Jitter on the digital output was very low in all areas, uncorrelated jitter hovering at 6pS across the audio band, with little high rate jitter above 20kHz. Signal related jitter (1kHz, -60dB test tone) measured a very low 10pS and low rate clock wander was also low at 45pS. These are excellent figures.
    The AK120 produced exceptional results for a portable player, improving even upon the excellent AK100. It has massive dynamic range, low distortion and negligible jitter and is way ahead of other portables, comparing with the best stand-alone DACs. NK

Frequency response (-1dB)
192k sample rate    4Hz-73kHz

Distortion (16 / 24bit)    %
0dB    0.0008 / 0.0008
-60dB    0.18 / 0.04

Separation (1kHz)                109dB
Noise (IEC A)                       -115dB
Dynamic range (16/24bit)    102dB/115dB
Output                                  1.6V


FREQUENCY RESPONSE    192kHz sample rate


DISTORTION     24bit, 0dB


DISTORTION     24bit, -60dB


EIAJ DYNAMIC RANGE  (–54.7 + -60)






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