Astel&Kern SP4000 Digital Audio Player
Built on Legacy, Evolving Perfection
The A&ultima SP4000 represents Astell&Kern’s latest flagship digital audio player, developed after three years of dedicated research and innovation following the SP3000.
As a member of the A&ultima series, Astell&Kern’s premier lineup featuring state-of-the-art technology and superior specifications, the SP4000 exceeds the standards set by the SP3000, previously considered the ultimate benchmark.
Utilizing an advanced Octa audio circuit design, the SP4000 captures the purest form of audio craftsmanship, delivering a sound experience that is refined, powerful, and exceptionally close to perfection. Elevate your listening with the SP4000 and explore sound at a new pinnacle.
- Enhanced signal processing capabilities with Octa audio circuit architecture
- Supports High Driving Mode for delivering premium sound quality
- Minimizes group delay with proprietary ESA (Enhanced Signal Alignment) technology
- Ultra Low Noise LDO Regulator for top-tier noise suppression
- Precision sound achieved with Any Layer Type PCB
- Equipped with a 99.9% Pure Copper Shield Can
- First Astell&Kern Device to Support Full Android OS
- First Astell&Kern Device to Feature Advanced DAR Technology
- Features 4.5th generation UI, combining functionality and emotional design
Enhanced Signal Processing Capabilities with Octa Audio Circuit Architecture
In the SP3000, the digital-to-analog conversion utilized a 1:2 signal processing ratio. The SP4000 advances this design to a 1:1 architecture, pairing each AK4191 digital processor directly with a single AK4499EX DAC. This configuration delivers digital signals precisely to one DAC without distributing noise, enhancing signal separation and processing accuracy. Through ongoing circuit technology innovation, the SP4000 achieves a true Quad DAC implementation, previously deemed unattainable due to noise challenges. Consequently, it attains a remarkable Signal-to-Noise Ratio (SNR) of 131dB, matching the performance of its predecessor’s independent dual audio circuit.
Supports High Driving Mode for
Premium Sound Performance
The SP4000 features twice as many OPAMPs arranged in parallel compared to its predecessor, delivering richer and more detailed sound. High Driving Mode provides powerful and stable output, much like a four-wheel-drive vehicle confidently navigating rough terrain. It’s designed to reproduce even the most delicate sonic details with precision, allowing you to enjoy deeper, clearer, and more immersive music.
Minimized group delay with proprietary ESA (Enhanced Signal Alignment) technology
The SP4000 incorporates Astell&Kern’s proprietary ESA (Enhanced Signal Alignment) technology, addressing the persistent issue of group delay in audio. This technology synchronizes frequency signals to arrive more consistently, reducing frequency distortion and substantially improving sound clarity and purity.
*What is Group Delay?
Group delay in audio describes the varying time intervals different frequencies require to travel through an internal system. Essentially, it means that each frequency reaches the output at slightly different moments, causing a phenomenon where frequencies within an audio signal do not arrive simultaneously, leading to minor delays.
Top-Tier Noise Suppression
(Ultra Low Noise LDO Regulator)
The SP4000 incorporates a newly designed LDO (Low Dropout) Regulator in its power supply, achieving up to a 97% reduction in noise compared to earlier models. LDO Regulators, known for their high performance, are commonly utilized in precision medical instruments and 5G communication systems. By stabilizing battery voltage and effectively minimizing noise, this component ensures a cleaner and more pristine audio output.
Precision Sound with Any Layer HDI PCB
To achieve the highest sound quality, the SP4000 incorporates top-tier Any Layer HDI (High-Density Interconnect) PCB technology. Commonly used in smartphones and high-performance electronic devices, this advanced circuit board allows for the precise design of complex circuitry within a compact space. It minimizes signal loss, enabling the delivery of a more refined and detailed sound.
Equipped with 99.9% Pure Copper Shield Can
The SP4000 is equipped with a precision-engineered Shield Can to block various types of noise and electromagnetic interference that could affect the audio block. For the first time in Astell&Kern's lineup, a 99.9% pure copper Shield Can is used, providing not only exceptional shielding performance but also delivering sound that is clearer and more distinct than ever before.
Astell&Kern’s First-Ever Full Android OS Integration
Astell&Kern has overcome Android OS’s sampling limitation (SRC) through its proprietary customization technology, ADP (Astell&Kern Direct Path). This allows for bit-perfect, lossless playback even in streaming environments, ensuring the highest possible sound quality during music listening.
[ Astell&Kern Direct Path Flow ]
In response to the growing shift toward streaming-based music consumption, Astell&Kern has integrated full Android OS for the first time.
The SP4000 not only delivers flagship-level audio quality but also offers enhanced convenience, marking its evolution into a highly refined next-generation digital audio player.
First-Ever Implementation of Advanced DAR by Astell&Kern
The SP4000 features Advanced DAR, Astell&Kern’s second-generation Digital Audio Remaster technology, which produces sound that is more natural and refined. Instead of sending the audio file directly to the DAR engine, the SP4000 first applies VSE (Virtual Sound Extender) to virtually recover lost harmonics, improving sound quality from the outset. Following this, the advanced DAR engine executes a second-stage upsampling with enhanced precision and completeness. This dual-stage process delivers a richer, more immersive listening experience that closely replicates the original recording.
[ Lossy audio above 16kHz ][ Data restoration through VSE ][ DAR applied after data restoration ]
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PCM 44.1kHz range PCM will be converted to 352.8kHz for playback
48kHz range PCM will be converted to 384kHz for playback
No conversion will be made when playing DSD with this option selected -
DSD PCM files lower than 96kHz will be converted to DSD128 for playback
PCM files over 96kHz will be converted to DSD256 for playback
DSD files below DSD256 will be converted DSD256 for playback with this option selected
* The DAR function can be turned on and off and you may select it to suit the source sound and your own preferences.
* Max PCM rate 384kHz/DSD64 conversion play is supported, and the files will be converted to and played in the sample rates that fit the source sound.
Drive Your Music, Latest Snapdragon Octa-Core CPU for the Newest Flagship Device
A&ultima SP4000 is equipped with a Snapdragon 6125 Octa-core processor, so you can enjoy the overwhelming sound, faster system response and a redesigned generation user interface that moves comfortably and smoothly.
Featuring a high-performance CPU and improved 8GB of DDR4 memory, which is twice the amount commonly used, the more powerful system is stable with fast and fluid movement.
The CPU, memory and wireless communication parts are configured as one module, with the digital circuit parts arranged in the same area creating a single system on a chip (SoC). This maximizes the efficiency of the overall circuit configuration by providing more audio-only circuit space as well as reducing heat and noise from digital circuits.
Enhanced 4.5th-Generation UI That Blends Function and Emotion
The SP4000 features an upgraded UI that balances both functionality and emotional experience. The main screen includes an immersive animation where an LP appears to slide in and out as you swipe through albums, turning the act of choosing music into a visually engaging and tactile experience.
The interface retains Astell&Kern’s signature Crimson theme, reflecting the brand’s identity and capturing its distinct emotional sensibility in a refined, modern design.
Material Innovations, Use stainless steel 904L on DAP body material
In pursuit of the A&ultima series’ mission to deliver unmatched value through innovative and meticulous design and craftsmanship, the SP4000 incorporates 904L stainless steel, a version of stainless steel never before used in a portable audio player. This choice elevates the device beyond a mere digital player, positioning it firmly within the realm of luxury goods.
904L stainless steel is notably harder and more challenging to work with than standard stainless steel, demanding considerably greater time and effort. Its exceptional durability and resistance to corrosion ensure it maintains its aesthetic appeal, which is why it is favored in high-end luxury watches where flawless materials and components are essential. Discover the unmatched elegance and luxury of the SP4000, crafted with the expertise and precision of Astell&Kern’s skilled artisans.
DAC Filter Selection
Enjoy personalized sound design by selecting from six DAC filters provided by Astell&Kern:
| Sound Type | Filter Name | Characteristics |
|---|---|---|
| Natural Tone | Super Slow Roll-off | No echo, reproduces natural sound |
| Acoustic Tone | Short Delay Slow Roll-off | Minimal echo, reproduces original sound |
| Traditional Tone | Slow Roll-off | Minimal echo, reproduces original sound |
| Harmonic Sound | Low Dispersion | Short echo, reproduces original sound |
| Acoustic Sound | Short Delay Sharp Roll-off | Post echo, reproduces bass sound |
| Traditional Sound | Sharp Roll-off | Pre and post echoes create powerful sound |
Crossfeed, Speaker effect when listening through headphones
Crossfeed mixes parts of the original signal from one channel and sends that signal to the opposite channel with a time difference to center the sound image. Through the use of detailed settings such as Shelf Cutoff, Shelf Gain, and Mixer Level, you can set the level of crossfeed according to your listening preferences.
Adoption of 6 inch 2180x1080 2K Display
Experience the SP4000 more conveniently and comfortably with a wide 6-inch, large-screen 2180x1080 2K display.
AK File Drop to enjoy wireless transfers
The new AK File Drop function in the SP4000 makes files transfers easier and more convenient. Using AK File Drop, you can freely transfer files wirelessly through a PC, smartphone, or FTP program located on the same network. Music file management is now possible with a cableless, wireless solution.
ReplayGain Automatically and Uniformly Adjusts Playback Volume
ReplayGain for Automatic Volume Level Adjustment ReplayGain functionality, which adjusts audio sources with varying volume levels to a uniform loudness, has been implemented. Enjoy your personalized playlists with the ReplayGain feature.
* ReplayGain supports up to 24bit/192kHz audio sources.
QC 3.0 Fast Charging Supported
The SP4000 supports Qualcomm QC 3.0 fast charging, so you can charge your DAP faster and more efficiently than previous models, reaching a full charge in about 5 hours.
Wireless Hi-Fi Sound via BT Sink
The BT Sink function allows you to connect the SP4000 to an external device via Bluetooth, similar to connecting a smartphone to a BT speaker. Music being played on the external device can be transmitted to the SP4000 through the BT Sink function.
Premium Shrunken Calf Leather Case from Germany’s Finest Leather House
The SP4000 is packaged with a premium leather case crafted from Shrunken Calf by Perlinger, Germany’s world-renowned leather house. Founded in 1864 and spanning five generations of craftsmanship, Perlinger supplies the finest leather to luxury brands across the globe, blending time-honored tradition with modern techniques.
The Shrunken Calf leather used in the case is made from the soft, delicate hide of calves under one year old. It is processed using a chrome tanning method to preserve its natural texture, then uniquely shrunk using special agents—not heat—to retain its organic grain and wrinkles.
Following an aniline dyeing process, Perlinger’s proprietary pigments are added to achieve a deep, vibrant color. Their advanced anti-aging treatment ensures that this richness lasts over time, complementing the SP4000 with a leather case that embodies lasting beauty, durability, and luxury.
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General Specifications
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Model
SP4000 (PPF51)
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Body Color
Black, Silver
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Body Material
Stainless Steel 904L
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Display
6inch 2K (2160 x 1080) touch screen
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Supported Audio Formats
WAV, FLAC, WMA, MP3, OGG, APE, AAC, ALAC, AIFF, DFF, DSF
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Sample rate
PCM : 8kHz ~ 768kHz (8/16/24/32bits per Sample)
DSD Native : DSD64(1bit 2.8MHz), Stereo | DSD128(1bit 5.6MHz), Stereo
DSD256(1bit 11.2MHz), Stereo | DSD512(1bit 22.4MHz), Stereo -
Output Level
Unbalanced 4.1Vrms │ Balanced 8.2Vrms (Condition No Load)
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CPU
Octa-core
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DAC
AKM4191 x4 + AKM4499EX x4 (Real Quad DAC)
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Decoding
Support up to 32bit / 768kHz Bit to Bit playback
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Input
USB Type-C input (for charging & PC & MAC)
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Outputs
Unbalanced Out (3.5mm), Optical Out(3.5mm)
Balanced Out (4.4m, only 5-pole supported) -
Wi-Fi
802.11 a/b/g/n/ac (2.4/5GHz)
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Bluetooth
V5.0 (A2DP, AVRCP, Qualcomm® aptX™ HD, LDAC, LHDC, SBC, AAC)
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Dimensions
3.34” (85mm)[W] x 5.89” (149.8mm)[H] x 0.76” (19.5mm)[D]
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Weight
About 21.7oz (615g)
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Feature Enhancements
Firmware upgrade supported (OTA)
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Operating Temperature
0℃ ~ + 40℃ (32℉~ 104℉)
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Model
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Audio Specifications
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Frequency Response
±0.006dB (Condition : 20Hz~20kHz) Unbalanced │ ±0.006dB (Condition : 20Hz~20kHz) Balanced±0.06dB (Condition : 20Hz~70kHz) Unbalanced │ ±0.06dB (Condition : 20Hz~70kHz) Balanced
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S/N
129dB @ 1kHz, Unbalanced │ 131dB @ 1kHz, Balanced
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Crosstalk
-136dB @ 1kHz, Unbalanced │ -145dB @ 1kHz, Balanced
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THD+N
0.0005% @ 1kHz, Unbalanced │ 0.0003% @ 1kHz, Balanced
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IMD SMPTE
0.0004% 800Hz 10kHz (4:1) Unbalanced │Balanced
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Output Impedance
Unbalanced Out 3.5mm (0.7ohm) │ Balanced Out 4.4mm(1.7ohm)
*Audio measurements are based on the Normal mode.
*Auto Mute is not used during audio testing.
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Frequency Response
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Clock Source
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Clock Jitter
25pS (Typ)
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Reference Clock Jitter
200 Femto Seconds
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Clock Jitter
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Storage Capacity
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Built-in Memory
256GB [NAND]
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External Memory
microSD x1 (Max. 1.5TB)
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Built-in Memory
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Battery
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Capacity
6,780mAh 3.8V Li-Polymer
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Charge Time
about 5hours (QC3.0 Charging)
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Playback Time
about 10hours (Standard : FLAC, 16bit, 44.1kHz, Vol.50, LCD Off)
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Capacity
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Supported OS
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Supported OS
Windows 10,11(32/64bit) MAC OS X 10.7
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Supported OS
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