After successfully launching the AK100 and the AK120 models, A&K asked themselves, “What is the ultimate sound quality?” After much consideration, A&K decided to move a step further with their goal, which is to deliver the sound “exactly as the artist had intended” for all to hear. Moving from the AK100 to AK120, A&K decided to provide a Dual DAC setup to create better left and right channel separation with clearer sound quality. A&K thought that the Dual DAC setup would be enough, but while developing the AK240, A&K felt the need to further improve sound quality in order to accurately reproduce the original sound recording. After countless hours of research and testing, A&K was 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, A&K can dare say that they have gotten “that much closer” to the sound quality of the original recording.
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.
Native DSD Support
One of the approaches A&K 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, A&K had to select a different DAC chipset. Making the decision to change the DAC was not easy, but in order to reach their goal, they had to make a bold move which was to start from scratch.
A&K has asked themselves: 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, A&K has 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, A&K needed a chip that will work with it. It took them a long time, but A&K made it work. Through countless hours of testing, they 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.
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.
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 A&K was able to move a step closer towards the original sound by then creating a balanced output terminal at the end.
- Model: AK240
- Body Color: Gun Metal
- Body Material: Aircraft Grade Duralumin
- Display: 3.31inch WVGA (480 x 800) AMOLED Touchscreen
- Supported Audio Formats: WAV, FLAC, WMA, MP3, OGG, APE(Normal, High, Fast), AAC, ALAC, AIFF, DFF, DSF
- Sample rate: FLAC, WAV, ALAC, AIFF : 8kHz ~ 192kHz (8/16/24bits per Sample)/ DSD Native : DSD64 (1bit 2.8MHz), Stereo / DSD128 (1bit 5.6MHz), Stereo
- Output Level: Unbalance 2.1Vrms / Balance 2.3Vrms (Condition No Load)
- DAC: Cirrus Logic CS4398 x2 (Dual DAC)
- Decoding: Support up to 24bit/192kHz Bit to Bit Decoding, DSD64/128
- Input: USB Micro-B input (for charging & data transfer (PC & MAC)) / Connection Mode : MTP (Media Device)
- Outputs: PHONES (3.5mm) / Optical Out (3.5mm) / Balanced Out (2.5mm, only 4-pole supported)
- Wi-Fi: 802.11 b/g/n (2.4GHz)
- Bluetooth: V4.0
- Dimensions: 2.59 ”(66 mm) [W] x 4.21 ”(107 mm) [H] x 0.68 ”(17.5 mm) [D]
- Weight: 6.5 oz (185 g)
- Feature Enhancements: Firmware upgrades supported (OTA)