Astell&Kern AK70 Portable Music Player

Balanced and Well-Connected

Equipment report
Digital-to-analog converters,
Music servers and computer audio
Astell & Kern AK70
Astell&Kern AK70 Portable Music Player

By now, unless you’ve been spending your time in a cave with no Internet access, you’ve heard of Astell&Kern. Although the company did not invent the portable personal music player, Astell&Kern has been a leader in portable audio ever since it introduced its first product, the AK100. Since then the maker has released a series of portable players that range from the AK Jr ($499) to the AK380 ($3499). Astell&Kern’s latest offering is the AK70 ($599), which is its least expensive player with balanced output connectivity. The AK70 also includes provisions for support (with a subscription) of Tidal, Groovers+, and MOOV streaming services, so you have your choice of either local (on the Micro SD card installed in the AK70) or, with Wi-Fi access, online music libraries.

Technical Details
The AK70 uses the same Cirrus Logic CS4398 DAC used in Astell&Kern’s AK100II. It can play back almost any musical file format currently available including up to 5.6MHz DSD. It recognizes and supports 384/32 PCM, but these files are internally down-sampled to 192/24 PCM during playback. The AK70 can also transfer DSD in native format through DoP, or it can convert DSD into PCM for output to portable DACs that do not support DoP.

The AK70 has two headphone outputs, a single-ended 3.5mm stereo connection and a 2.5mm balanced jack. Both have a maximum output of 2.3VRMS. Other output options include line-level analog (a full-level analog output that bypasses the volume control) and USB (so you can use the AK70 with an outboard DAC) as well as network playback via Wi-Fi. You can also use the AK70 as a stand-alone DAC via its USB connection; the limitation is that used as a DAC the AK70 only supports up to 96kHz/24-bit plyaback. For additional flexibility A&K also allows 48kHz/24-bit streaming over aptX Bluetooth HD.

Another very useful feature is “AK Connect,” which allows the AK70 to connect via a Wi-Fi network to a network attached storage (NAS) drive. When you are at home you can play any and all music contained on your NAS drive, including 192/24 PCM and 5.6 DSD. (For the record, after selecting a DSD file I did experience an initial delay of about two seconds before it began playing.)

The AK70 has one micro-smart-card slot that can support up to a 256GB card. With an internal memory of 64GB, you can max out the AK70 with 320GB of music files (some space is reserved for OS files). While that is not sufficient to carry an entire mature music library, unless you are doing a 500-day around-the-world walk-a-thon the AK70 should provide enough storage space to handle your comings and goings. When you’re at home, the amount of onboard storage becomes moot since you have access to your entire music library on your NAS via AK Connect. Although the AK70 uses an Android operating system it is not open to the point where you can add apps from the Play Store. Currently the U.S. version of the AK70 comes loaded with the aforementioned Tidal, Groovers+, and MOOV.

Ergonomics and Everyday Use
Since the development of its AK100, Astell&Kern has maintained certain signature physical design characteristics, such as a rotary, side-mounted volume knob, that have been included once again on the AK70. But unlike the AK100, where the volume knob stuck out, or the AK120 where a protective barrier beside the knob was used (similar to the kind seen on Panerai wristwatches), the AK70’s volume knob is recessed into the body of the player. To avoid “squareness” the AK70 has a slightly curved section to the right of its TFT LCD touchpad display. The AK70’s stock color is mist green, but since its original release A&K has also issued several special-edition black options in select markets. When compared to A&K’s other offerings the AK70 could very well be the most “sensible” physical design and shape. Neither too tiny nor too husky, and shirt-pocket-able, the AK70 is small enough to take on any trip, but not so miniscule that it’s easily lost.

With its 2200mAh 3.7V lithium polymer battery the AK70’s play time will vary—as it does with all portable players—based on the amount of power drain, which depends on the bit rate of the files played through it. A&K does not provide a battery-life specification, but I never ran out of juice at home. Even on a recent trip the AK70 was still going strong when I reached my destination. Accessory battery power supplies have gotten so inexpensive and ubiquitous that anyone who frequently travels should have at least one in his kit, which makes portable player (or smartphone) battery life less critical. Recharge time was under three hours from completely exhausted to full battery level.

I used the AK70 with a wide variety of headphones. With extremely sensitive in-ears such as the Empire Ears Zeus there was no continuous background hiss or noise, but when I used AK Connect I did hear a bit of low-level random noise during the silence before a track began to play. Going to the other extreme, the AK70’s single-ended output drove my pair of Beyerdynamic DT 990 600-ohm version to adequate volumes at an indicated level of 125 out of a maximum level of 150. Using a Silver Dragon adapter cable from Moon Audio, I could use the MrSpeakers Ether Flow headphones in balanced mode with an average volume setting of 110. With both of these less sensitive ’phones there was no noise in the silences before tracks began to play.