Audio Streams

The AK240 came preloaded with a bunch of music, including Led Zeppelin's II in 24/192, and the flipping and fading from one channel to the other in "Whole Lotta Love" was pure head-spinning pleasure. While I've heard more lush, ripe presentations, the AK240-Viso combination delivered every last ounce of detail and nuance. Upper frequencies were finely detailed, yet never edgy or too sharp. Engaging the preloaded Pro EQ setting helped fill out the midrange with a bit more body, which I found preferable to the flat, default EQ setting. You can also create custom equalizations by entering EQ mode, drawing your preferred frequency response on the screen, then fine-tuning it by sliding the resultant settings up or down for each of the 10 bands.

Acoustic music, such as John Cage and Lou Harrison's Double Music, from the New Music Consort's Pulse (24/96, New World/Classic 80405), really showed off the AK240's resolving abilities. The complex harmonics of the percussion quartet sounded rich and full-bodied, never dry, fragile, or irritating. A favorite recording—an arrangement of La vallée des cloches (The Valley of Bells), from Ravel's Miroirs, arranged for orchestra by Percy Grainger and performed by Simon Rattle and the City of Birmingham Symphony Orchestra on the Grainger collection In a Nutshell (16/44.1 rip from CD, EMI 56412)—highlighted the AK240's way with presenting space through decay; and there was no sense of the foreshortening I've heard through lesser systems. Ravel's bells rang out sweet and clear, and trailed off into the distance, delivering a real sense of place (and longing). Ali Akbar Khan's Indian Architexture (DSD, Water Lily Acoustics WLA-ES-20-SACD) features a stunning set of four 20+-minute ragas—the AK240 handled their subtle shadings beautifully.

AK240 as DAC and USB-to-TosLink converter
You can connect the AK240 to your hi-fi in two ways: directly, using its line out; or as a USB DAC, using your computer as source. I used it in the latter mode, so I could continue using my iPad as a system controller. Otherwise, with the AK240 used as a source and leashed directly to my Pass Labs INT-30A amp, I'd have to get up and walk over to it every time I wanted to change tracks—which just seemed too odd, considering that the AK240 is a portable player. (A Bluetooth remote control, $49.99, is now available.)

I connected the AK240 to my MacBook Pro laptop with the included USB-to-Micro-USB cable, and to my Pass Labs with a length of AudioQuest Victoria cable. What I heard pretty well mimicked the AK240's sound through the NAD Viso HP50 headphones: at once resolute and finely detailed. The slight thinness I'd heard through the 'phones became more evident through my main system, making less-than-stellar recordings sound a bit rough around the edges. On the other hand, great-sounding recordings, such as Santana's Abraxas in DSD (Columbia/Legacy), were given their due by the AK240. In my experience, DSD recordings can offer a more dimensional sound than PCM, a quality nicely conveyed by the AK240.

My reference DAC, an Auralic Vega (footnote 2) is, to my ears, more full bodied, with greater fluidity and a more natural sound overall. In direct comparison, the AK240 sounded a bit lightweight, slightly bright, and thinned things out. The Vega has a very rich sound, and its top end, in particular, is full of body and sparkle with no hint of glare. That dimensional quality of DSD recordings is even more obvious through the Vega—they sound almost 3D. But I'm comparing the sounds of a $3500 DAC and a $2500 portable player; keeping that in mind, the AK240 held up its end very well—and you sure can't fit a Vega in your pocket.

While the AK240's TosLink output is limited to PCM playback (no DSD), I figured it was worth taking for a spin. For those who own an S/PDIF DAC without a USB input, the AK240 can act as a bridge to computer-based playback. I leashed the AK240 to the Auralic Vega DAC with a length of TosLink and did some listening. Many of the Vega's sonic traits remained, although the relative thinness I'd heard through the line-level output persisted here as well.

The AK240 can also communicate with a Bluetooth-enabled receiver. Unfortunately, I was fresh out of same at the time of this review, so I can't report on this aspect of the AK240's performance. From my past experience, Bluetooth's sound quality is passable—more important, it permits easy connection between portable devices and hi-fis.

In terms of direct competition, the Astell&Kern's mix of features and functions puts it in a class unto itself. Of course, there are now a host of portable players, including a number of much cheaper models from FiiO and HiFiMAN, but the most popular by far is your smartphone. A tip for Apple iPhone users: Onkyo's HF Player app (available at the iTunes Store) lets your iOS device play FLAC files, as well as resolutions up to 24/192 and DSD. To reap the rewards of these higher resolutions, you need to bypass your iPhone's internal DAC by using the Lightning-USB camera adapter and a suitable outboard DAC.

I also had on hand a review sample of Sprint's HTC One (M8) Harman/Kardon Edition phone ($799.99), which can play up to 24/192 PCM files. Playing hi-rez files and CD-quality music, the AK240 pretty much crushed the HTC One, which sounded threadbare in comparison, and pretty uninspiring through its stock earbuds. The NAD Viso 'phones certainly helped fill things out, and this combo offered respectable sound, especially for a smartphone, if still no match for the AK240. Still, the HTC One (M8) Harman/Kardon Edition may very well fill the bill for those who don't want to carry around two devices and would like the ability to play hi-rez files on the go.

I'd also be remiss if I didn't mention Neil Young's Pono player, which will also be able to handle up to 24/192 playback through its internal DAC (for all intents and purposes, an Ayre Acoustics design). While review samples of the Pono have yet to ship, I think we can thank Young for raising the profile of hi-rez music with his Kickstarter campaign for the Pono, which raised over $6 million from 18,220 backers.

Niggles
When I tried to use the AK240 to play bigger files (24/192 and DSD) in MQS mode via WiFi, the long and frequent dropouts made them unlistenable. I was able to play the same files when the AK240 was attached to my iMac by a wired connection. That said, WiFi performance is notoriously site-specific; your mileage may vary.

After a firmware upgrade of the AK240, I found I had to rebuild my MQS library by clicking "Rebuild" in the MQS app on my iMac. Before I did that, the player could find none of the individual tracks I'd chosen to play, even though the album/track info appeared on the player. The rebuild solved this problem.

An operational anomaly: When streaming through MQS mode, the current selection didn't show up on the unit's home screen. Instead, the name of last recording played from its internal hard drive continued to be displayed.

"A Thing of Beauty . . .
. . . is a joy to hold forever," to paraphrase John Keats. Is it wrong to love the AK240 for its physical beauty? I suppose if it sucked as a music player, that would be plain folly. Thankfully, it doesn't. From its app to its output, the Astell&Kern AK240 delivers a rich user experience. Driving NAD's Viso HP50 headphones, it provided a rewarding sound from files ranging from CD to DSD quality and every resolution in between. Its combined strengths of superb resolution and clean, clear, fatigue-free reproduction made it a joy to listen to. Add its ability to function as a hi-rez DAC or USB-to-S/PDIF converter, and the fact that it's a thing of physical beauty just adds to its multitasked pleasures.

---

Footnote 2: Click here and here for AudioStream and Stereophile reviews.