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Astell & Kern AK240 Ultimate Portable Digital Audio Music Player
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Astell & Kern AK240 Ultimate Portable Digital Audio Music Player

£1,833.33 Exc. VAT |  


Manufacturer:  Astell & Kern

Astell & Kern AK240 Ultimate Portable Digital Audio Music Player 

Closer to Original Sound

After successfully launching the AK100 and the AK120 models, we asked ourselves, “What is the ultimate sound quality?” After much consideration, we decided to move a step further with our goal, which is to deliver the sound “exactly as the artist had intended” for us to hear. Moving from the AK100 to AK120, we decided to provide a Dual DAC setup to create better left and right channel separation with clearer sound quality. We thought that the Dual DAC setup would be enough, but while developing the AK240, we felt the need to further improve sound quality in order to accurately reproduce the original sound recording. After countless hours of research and testing, we were able to find the answer.

The answer was to create both a balanced output and native DSD playback through the Dual DAC setup.
Now with the AK240, we can dare say that we have gotten “that much closer” to the sound quality of the original recording.  

Native DSD Support

What is DSD? DSD (Direct Stream Digital) is a digital audio file format originally developed for SACDs (Super Audio CD). Regular digital audio file formats such as PCM (Pulse Code Modulation) is separated into 65,000(16bit) to 16,700,000(24bit) of information on the Y axis, and 44,100(44.1kHz) to 192,000(192kHz) across the X axis for digital signals. DSD files have 1bit (0s or 1s) for Y axis and is separated into 2,800,000(2.8MHz) to 5,600,000(5.6MHz) of information for X axis.

Compared to regular audio CDs with 16bit/44.1kHz PCM format, SACD’s recording frequency goes up to 100kHz and the dynamic range goes beyond 120dB while maintaining sound clarity during the transmission.

One of the approaches we decided that would help us move a step closer to the original sound quality was to provide native DSD playback without having to convert it into PCM. This was indeed a difficult task. In order to provide native DSD playback on the AK240, we had to select a different DAC chipset. Making the decision to change the DAC was not easy, but in order to reach our goal, we had to make a bold move which was to start from scratch.

We have asked ourselves: Does the DAC support Native DSD? Will it allow for the Dual DAC setup? What else is needed for the perfect Native DSD support?

In order to answer these three questions, we have decided to use the Cirrus Logic CS4398 chip in the Dual DAC setup with an added exclusive XMOS chip that will allow for Native DSD support.

The process of setting up Native DSD support was not an easy task. Since the main CPU does not process Native DSD, we needed a chip that will work with it. It took us a long time, but we made it work. Through countless hours of testing, we were able to achieve Native DSD playback by having the main CPU process the data, send it to the exclusive XMOS chip, then through the DAC to deliver the sound.

Balanced Output

Unbalanced vs. Balanced Output. The unbalanced method is the most commonly used basic method which consists of “left and right signals + ground line”. This setup includes a ground line which blocks out external noises from the outside. However, since the ground line cannot block out all of the external noises completely, external noises can be mixed into the signals that are transmitted, which then result in changes to the sound. The longer the signals travel, the more external noises that will be mixed into the sound which is why it is used within a short distance of 1 to 2 meters.

Unlike the unbalanced method, the balanced method has an additional cold signal to compliment the hot signal which reduces the external noises.

The balanced method has a few advantages over the unbalanced method. The first advantage is that the hot signal and the cold signal will remove the external noises received. The second advantage is increased output due to the 2 transmitted signals.

Since the ground line cannot block out 100% of the external noises, noise will appear on both the hot and cold signals. The alignment of the 2 signals allows the noise to usually appear at similar points where they will eventually be removed as the signals are transmitted.

Dual DAC meets Balanced Output

It did not take us long to figure out that the AK240’s Dual DAC and balanced output resulted in the best sound. During the development of the AK100 and AK120, Astell&Kern's specific analogue amp setup was already creating full balanced analogue signals streaming from the DAC and we were able to move a step closer towards the original sound by then creating a balanced output terminal at the end.

Astell&Kern has created the AK120 Titan with a storage capacity of 128GB, but in order to support Native DSD, MQS, and massive audio files, we had to come up with the ultimate portable music player with 256GB of storage. With 256GB of internal memory, about 2,500 MQS (24bit/96kHz, 4 minute-long, 90MB) songs can be saved. With the addition of a 128GB microSD card, the AK240 can support up to a total memory capacity of 384GB.


Color Gunmetal
Body Material Duralumin (Aircraft grade)
Display 3.31-inch WVGA (480 x800) AMOLED capacitive
File format WAV, FLAC, WMA, MP3, OGG, APE (Normal, High, Fast), AAC, ALAC, AIFF, DFF, DSF
Sampling rate FLAC, WAV, ALAC, AIFF: 8kHz ~ 192kHz (8/16/24/32bit (float / Integer))
* 32bit integer is down-converted to a 24bit
  DSD native: DSD64 (1bit 2.8MHz), stereo / DSD128 (1bit 5.6MHz), stereo
Output Level Unbalanced 2.1Vrms + 2.1Vrms / balance 2.3Vrms + 2.3Vrms (no load)
Decode Up to 32bit (float / Integer) / 192kHz bit to bit decode
* 32bit integer is down-converted to a 24bit
Input terminal And data transfer (charging USB micro-B input (PC & MAC)
Connection mode MTP (Media Device)
Output terminal (2.5mm, 4 contacts only) (3.5mm) / optical digital output (3.5mm) / balanced output headphone out
Wi-Fi IEEE 802.11 b / g / n (2.4GHz)
Bluetooth V4.0 (A2DP/AVRCP)
Size 66mm [W] x 107mm [H] x 17.5mm [D]
Weight 185g
Other Features Firmware upgrade (OTA)
Frequency characteristic ± 0.023dB (20Hz ~ 20kHz) unbalanced balance ± 0.3dB (10Hz ~ 70kHz) unbalanced balance
S / N ratio (Unbalanced 1kHz/0dB, 48kHz/24bit, no load) 116dB
(Balance 1kHz/0dB, 48kHz/24bit, no load) 117dB
Crosstalk (Unbalanced 1kHz/0dB, 48kHz/24bit, no load) 130dB
(Balance 1kHz/0dB, 48kHz/24bit, no load) 135dB
THD + N (Unbalanced 1kHz/0dB, 48kHz/24bit, no load) 0.0007%
(Balance 1kHz/0dB, 48kHz/24bit, no load) 0.0005%
IMD 0.0004% (unbalanced 800Hz 10kHz (4:1))
0.0003% (balance 800Hz 10kHz (4:1))
Output Impedance
Clock jitter 50ps (Typ)
Embedded memory Including the 256GB NAND flash * system area
Expansion slot microSD (up to 128GB) x 1
Battery 3,250 mAh 3.7V lithium polymer battery
Support OS Windows ® XP, Windows ® Vista, Windows ® 7,8 (32/64bit)
10.6.5. Above MAC OS X


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