Despite the cost and a few oddities, the AK500N network media player delivers flawless audio playback. Stephen Dawson reports.

Astell & Kern is a brand name of South Korean firm iriver, once known for its portable music players. As indeed is Astell & Kern. Rather than continuing to compete on Apple’s turf, Astell & Kern players are shooting for the very high end, very premium market. Its latest premium portable sells for over $5,000.

Given that you have the high end tech, though, why not bring it to the home? That’s what the AK500N network media player does.

What is it?

The Astell & Kern AK500N plays digital media from its internal storage and from network sources. It has a built in slot-style CD drive so that you can easily transfer your CDs to the unit (you get a choice of FLAC or WAV for storage – FLAC will reduce space demands by around 40%). It is not a CD player, though. The drive is only for ripping.

The unit has a 1TB solid state drive built in, but there are bays for four drives and these are user-installable so you can bump up storage to an enormous level if you wish. RAID 5 configuration is provided so it all looks like one big drive and there’s some data integrity protection using one of the drives.

The unit can also serve up its contents to your network via DLNA so if you have a player in another room, or one of the proliferating multi-room systems, you can play back its music with those. Or it can play music from other servers on the network via DLNA. It will perform duty as a DLNA digital media renderer, which means you can use third party apps on Android and iOS devices to send music to it.

(There are apps for iOS – AK Connect and AK Connect HD – which are supposed to be able to be used as controllers for the system. I could only get them to recognise the unit as a digital media renderer, and not as a server.)

The unit connects to your network via Ethernet or WiFi (2.4GHz band only supported, it appears). It can also act as a DAC for your computer (via the USB-B input) and to various consumer and professional digital sources (optical, coaxial, BNC and AES/EBU digital inputs).

There’s also a USB socket on the side, plus one at the rear, so you can plug in flash storage or an external hard drive. Plus a micro-SD slot. Just in case, I guess.

There is a wealth of outputs: stereo analogue (both fixed and variable level), stereo balanced XLR (both fixed and variable level), 6.5mm headphone, 3.5mm headphone, 2.5mm balanced headphone and the same four types of digital audio.

What it won’t do is worth mentioning: there is no internet audio – internet radio, Pandora, Spotify – and no Apple Airplay. There is a music store accessible through the unit, but it is apparently only available to Korean residents.

All this is packed into a solidly built and heavy (over 11kg) metal box. This is not a component style unit. It would fit into a cubical container measuring 250mm on a side. The connections are on the back, except for the headphones, USB and SD sockets which are on the side. On that side is also a large volume control. A 178mm touch screen display on the top can fold up for more convenient use.

The operating system seems to be a heavily skinned version of Android.

The unit supports just about all audio formats: WAV, FLAC, WMA, MP3, OGG, APE, AAC, ALAC, AIFF, DFF and DSF. These last two are Direct Stream Digital, with both regular (DSD64) and DoubleDSD (DSD128) handled. PCM up to 384kHz and 24-bit is decoded.

One last thing: the unit has a Lithium-Ion battery built in. The idea is to provide greater isolation from noise on the mains. The battery takes around three hours to charge and is good for around seven hours of playback. Of course, you can use the unit with the power plugged in.

Setting Up

Gosh I hate the modern tendency to scant included instructions. Especially when they can make you think your $17,000 purchase is defective. The multi-language quick start guide attempts to squeeze all you need to know on a single sheet less than A5 in size. What it doesn’t say is that you have to set the output.

I plugged the unit’s fixed level analogue outputs into my audio system, selected one of the tracks already in the unit and started it playing. But there was no sound. Perhaps there was something wrong with my system, or the track, so I plugged in a set of headphones. Still nothing.

I started exploring the setup menus to see if there was anything obvious I needed to do. Actually, yes. Within ‘Setup’ you choose ‘Sound’, then ‘Sound input/output’. This brings up a graphical display of all the output options (three headphone options, four digital audio options, four analogue audio options). Touch the one that you want and sound instantly emerges from the depicted output.

Why? What’s wrong with feeding to multiple outputs? Or, at least, employing the headphone convention where inserting the plug enables it. If it didn’t look so very pretty, I’d have to say it’s a very clunky way of implementing output management.

Otherwise things were pretty straightforward and forgiving. You have to switch on the network functions to access music on or serve up music to your network, but the setup menu’s pretty clear and not very long, so all that’s easy.

Even though the unit will only rip to WAV or FLAC, you can load it up with existing music in your other formats. Just plug your Windows computer into its USB-B socket (you’ll need software from A&K’s website for a Mac). The unit’s music storage section appears using the Media Transfer Protocol common to Android devices, so you can just drag music folders into it. After a few seconds they become available for playback using the usual Songs/Artist/Albums/Genres/Folders/Playlists options. You can also copy music back to your computer by means of the same connection.

This USB-B doubles for using the unit as a USB DAC with a computer. A driver is required for Windows (the full manual, drivers and so on are on the unit’s built in solid state drive, and so can be easily accessed). Plugging it into my Mac it worked with my music files up to 192kHz and both DSD64 and DSD128. With a 352.8kHz PCM file there was a lot of noise. Perhaps my Mac or the cable I was using wasn’t up to the task.

Fact is, I wouldn’t use it for a computer DAC because when in such a mode it is locked into that functionality and can’t be used for anything else. It does, however, usefully display the signal input on its display in this mode.

Performance

The first thing to note is that the line output is pretty hot, perhaps six decibels louder than usual. That typically won’t cause problems, other than sometimes leading to a hasty reduction in the level after having switched from some other source.

In general the interface worked smoothly and reliably. The unit, as supplied, had a few hundred gigabytes of content in a variety of formats, presumably the detritus left by other reviewers (a small number of high resolution sample tracks are provided with the unit). Some of these were unplayable (DSD256). Quite a few weren’t properly tagged, but could still be played via the ‘Folders’ access route. (This was also the only way to access music on a plugged-in USB drive.)

Just occasionally the interface would pause for a couple of seconds while it thought about things. I found it best to power down the unit each evening so that each day it scored a fresh boot up for what lay ahead. It displays cover art and track information.

The sound was top notch. There isn’t really much to say about it other than that the unit delivered precisely what was in the file to the very best that it can be delivered. It did it consistently, smoothly and delightfully.

I used both the 3.5mm and 6.5mm headphone outputs and the results were quite up to the standard of the rest of unit (aside from the silliness of having to work through the menu system to change the output). In particular, there was without doubt sufficient volume to drive any headphones to damaging levels should you want that. Used at more reasonable levels, it delivered first class detail and even possible nuance within high resolution music.

The unit has a ‘gapless’ mode for allowing run-on tracks to be played back without a space between them. This worked on tracks contained on the unit’s internal storage, but not for music being played from the network.

The unit did a good job on ripping CDs. It uses the GraceNote CD information system to identify inserted CDs and apply tags (but not cover art) to the ripped files. I checked it with some fairly obscure commercial discs, but it had no trouble finding them.

The ripping is fairly slow as the unit takes care to read things accurately. I tried a few significantly scuffed CDs I maintain for the purpose and it managed an error free result on them. With a nice clean CD of 53 minutes, it took only a few seconds to identify the tracks, and then 15 minutes and 48 seconds to rip and encode them to FLAC at the ‘Fast’ setting. You can go faster (at risk of error) or slower, and apply error correction.

But for some reason it doesn’t index the ripped files with the rest of its content. Instead you have to go to a special menu item called Ripped CDs to access them. I even tried moving them around in the unit’s storage, to no avail. But when I copied in a folder of music ripped from a CD by my computer, it indexed normally.

I conducted a few tests. With CD-standard music the frequency response extended to 21,000Hz at -0.1dB. For 192kHz signals the response rolled off smoothly to be down by 2dB at 50,000Hz (-3dB at 58,000Hz). With DSD64 the output was -1dB at 33,000Hz and -3dB at 40,000Hz (oddly, since -3dB at 50,000Hz is recommended for DSaD64). With DSD 128 the output remained undiminished out to 33,000Hz, then rolled off rapidly to be down by 3dB at 48,000Hz.

The noise levels were significantly different when used while connected to power or when run from the built in battery. Using 24-bit signals, the noise level, A-weighted, was -103.4dB when running from power, and -108dB while on the battery. Looking at the noise graph, the noise profiles were the same from 3kHz and up, but below that the power-connected noise levels rose smoothly from -140dB to -100dB by 20Hz. On the battery the -140dB level (or better) was maintained down to 100Hz, with noise level rising a little to -130dB by 20Hz.

This both puzzling and likely unimportant. When running the unit extensively for many days on power, I did not once notice an increased noise floor, nor was there any detectable audible enhancement from switching to battery. But I don’t understand why there should be a higher noise floor in the midrange and bass from power. There were no spikes related to the 50Hz mains. Perhaps spurious noise was being generated by the battery charging circuitry. Certainly I’ve seen nothing like it with other mains-powered DACs.

Another oddity was that the stereo crosstalk was a solid -106.9dB on battery power, but only -97.6dB on mains. Again, the divergence was in the midrange and bass, beginning a bit above 3kHz, with a 60dB divergence by 20Hz. Again, this had no apparent audible effects, nor should it be expected to have.

Conclusion

Obviously, at $17,000 the Astell & Kern AK500N isn’t for everyone; however, for those with plenty of money and the desire to have their network audio delivered by a somewhat classier affair than the typically industrial-looking NAS would do well to consider this unit. That its capacity can be user upgraded is something rare for high-end network audio products.