Astell & Kern
Expected Jun 26, 2025
A&ultima SP4000 DAP Music Player
$3,900.00 USDFeatures
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
What's in the Box?
Warranty
The A&ultima SP4000 DAP is Astell&Kern's new flagship digital audio player, delivering a sound experience that's refined, powerful, and remarkably close to perfection. As part of the A&ultima series–Astell&Kern’s flagship lineup combining cutting-edge technology and top-tier specifications—the SP4000 surpasses the boundaries set by the A&ultima SP3000 DAP, once regarded as the ultimate audiophile reference music player.
The SP4000 DAP is the result of three years of relentless research and innovation following the development of the SP3000. Built upon an advanced Octa audio circuit architecture with true Quad DAC implementation, the SP4000 surpasses the boundaries set by the SP3000, delivering an exceptional 131dB SNR.
This is the first Astell&Kern product with full Android OS integration, enabling bit-perfect lossless streaming through proprietary ADP (Astell&Kern Direct Path) technology. The SP4000 introduces Advanced DAR (Digital Audio Remaster) with VSE technology for enhanced restoration, powered by a Snapdragon 6125 Octa-core processor with 8GB DDR4 memory. Crafted from 904L stainless steel–a first in portable audio–it features cutting-edge technologies including enhanced signal alignment for minimized group delay, Ultra Low Noise LDO Regulator providing 97% noise reduction, and a 99.9% pure copper Shield Can for superior electromagnetic shielding.
Revolutionary Audio Architecture
True Quad DAC with Octa Audio Circuit Technology
The SP4000 portable music player marks a breakthrough in high-end portable audio engineering. While the SP3000 used a 1:2 digital-to-analog processing ratio, the SP4000 evolves to a precision 1:1 architecture. Each AK4191 digital processor pairs with a dedicated AK4499EX DAC, delivering digital signals directly without noise distribution.
Through continuous research and innovation in circuit technology, the SP4000 successfully implements a true Quad DAC—a feat previously considered impossible due to noise and other issues. As a result, the SP4000 achieves an impressive SNR (Signal-to-Noise Ratio) of 131dB, on par with the independent dual audio circuit of its predecessor.
High Driving Mode with Parallel OPAMP Configuration
The SP4000 features twice as many OPAMPs arranged in parallel compared to previous models, delivering richer and more detailed sound. The amp's 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.
Unlike OPAMP series configurations that increase noise while boosting power, the SP4000's parallel alignment expands the driving range horizontally with no noise increase or SNR reduction. This results in enhanced dynamic range and superior sound detail.
[OPAMP: Series Configuration]
Driving range increases linearly, but with increased noise and reduced SNR. While the sound may feel more powerful, it tends to become rougher or harsher.
[OPAMP: Parallel Configuration]
The driving range expands horizontally, with no increase in noise or reduction in SNR. This results in increased dynamic range and enhanced sound detail.
ESA Technology: Eliminating Group Delay
Astell&Kern's proprietary Enhanced Signal Alignment (ESA) technology addresses one of audio's most persistent challenges—group delay. ESA aligns frequency signals to arrive more uniformly, minimizing frequency distortion and dramatically enhancing sound clarity and purity.
Group delay occurs when different frequencies pass through a system at varying speeds, causing slight time differences that blur audio precision. ESA technology ensures all frequencies arrive simultaneously for pristine, coherent sound quality.
Premium Hardware Engineering
Ultra Low Noise Power Supply
The SP4000 incorporates a newly implemented LDO (Low Dropout) Regulator that reduces noise by up to 97% compared to previous models. These high-performance components, typically reserved for precision medical devices and 5G communication equipment, stabilize battery voltage and effectively suppress noise for exceptionally clean, pure sound reproduction.
Advanced PCB Technology
To achieve maximum sound quality, the SP4000 DAP features top-tier Any Layer HDI (High-Density Interconnect) PCB technology. This advanced circuit board design, commonly used in smartphones and high-performance electronics, enables precise routing of complex circuitry within compact spaces while minimizing signal loss for refined, detailed sound delivery.
[ SP3000 Layer Structure ]
[ SP4000 Layer Structure ]
99.9% Pure Copper Electromagnetic Shielding
For the first time in Astell&Kern's lineup, the SP4000 employs a precision-engineered Shield Can made from 99.9% pure copper. This advanced shielding blocks electromagnetic interference and various noise sources that could affect the audio block, delivering high-quality sound that is clearer and more distinct than ever before.
Next Generation Software Integration
First-Ever Full Android OS Implementation
Astell&Kern has overcome Android OS's inherent sampling limitations through proprietary ADP (Astell&Kern Direct Path) customization technology. This breakthrough enables bit-perfect, lossless playback even in streaming environments, ensuring the highest possible sound quality during music listening. The SP4000 delivers flagship-level audio quality while offering enhanced convenience, marking its evolution into a refined next-generation digital audio player. Enjoying hi-res audio has never been easier.
Advanced DAR: Second-Generation Digital Audio Remaster
The SP4000 introduces Advanced DAR, Astell&Kern's enhanced Digital Audio Remaster technology that delivers more natural, refined sound than ever before. Rather than sending the audio file directly to the DAR engine, the SP4000 first uses VSE (Virtual Sound Extender) to virtually restore lost harmonics, enhancing the sound quality at the initial stage.
Then, the advanced DAR engine performs a second-stage upsampling process with greater precision and completeness. This two-step approach allows listeners to enjoy a deeper, more immersive sound that comes closer than ever to the original recording.
[Lossy audio above 16kHz]
[Data restoration through VSE]
[DAR applied after data restoration]
DAR Processing Options:
- PCM Mode: 44.1kHz range converts to 352.8 kHz, 48 kHz range converts to 384 kHz. No conversion will be made when playing DSD with this option selected
- DSD Mode: PCM files under 96 kHz convert to DSD128, over 96 kHz convert to DSD256. DSD files below DSD256 will be converted to DSD256 for playback with this option.
*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.
High-Performance Processing
Flagship-Level CPU Performance
The SP4000 is powered by a Snapdragon 625 Octa-core processor delivering overwhelming sound quality, faster system response, and smooth user interference operation. Enhanced with 8GB of DDR4 memory–double the standard amount–the system provides stable, fast, and fluid performance.
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 User Experience & Design
4.5th-Generation UI
The SP4000 features an upgraded user interface that balances functionality with emotional engagement. The main screen includes immersive animations where LP albums appear to slide in and out as you swipe, transforming music selection into a visually engaging, tactile experience. The interface maintains Astell&Kern's signature Crimson theme, reflecting their brand identity in a refined, modern design.
With balanced 4.4mm and 3.5mm outputs and a high-quality amplifier, the SP4000 is compatible with your favorite high-end audio products, from IEMs (In-Ear Monitors) to headphones and earphones. The SP4000 pushes the boundaries of portable audio player performance with 256GB of internal memory with support for microSD cards up to 1.5TB, dual band 2.4/5Ghz Wi-Fi, DLNA networking, USB digital audio output, USB-C for data transfer and charging, and the ability to use the SP4000 as a USB DAC for your Mac or Windows-based PC. The SP4000 adds support for both aptX Adaptive and LDAC codecs to provide audiophiles with multiple options for 24-bit audio playback wirelessly to their audio system.
The SP4000 will add Roon Ready support pending completion of testing and final certification by Roon Labs.
Edge
Clean, angular lines echo the device's physical design
Simple
Intuitive interface with unobtrusive graphics for distraction-free use
Sensibility
Motion effects enhance emotional engagement and user interaction
Advanced Audio Customization
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 Technology
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.
Smart Features and Connectivity
Real-Time LED Information Display
The LED light surrounding the power button provides visual information about the currently playing song's Bit Depth while adding an aesthetically pleasing element. LED functionality can be customized according to user preferences.
ReplayGain Volume Normalization
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.
Wireless File Transfer: AK File Drop
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.
Bluetooth Hi-Fi: BT Sink Function
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 Display and Charging
6-Inch 2K Display
Experience enhanced convenience and comfort with a large 6-inch, 2180x1080 2K display that makes navigation and music management effortless.
PD 3.0 Fast Charging
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 4 hours.
Luxurious Materials and Craftsmanship
904L Stainless Steel Construction
To achieve the A&ultima series goal of providing unmatched value through innovative, uncompromising design and craftsmanship, the SP4000 uses 904L stainless steel—never before attempted in portable audio players. This material elevates the device from a digital tool to a luxury item.
904L stainless steel is significantly harder and more challenging to process than standard stainless steel, requiring substantially more time and effort. However, its exceptional durability and corrosion resistance ensure lasting beauty—the same qualities that make it the choice for expensive luxury watches where material perfection is paramount. Experience the uncompromising beauty and luxury achieved through Astell&Kern's expert craftsmanship.
Premium German Leather Case
Each SP4000 includes 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 worldwide, blending time-honored tradition with modern techniques.
The Shrunken Calf leather comes from the soft, delicate hide of calves under one year old, processed using chrome tanning to preserve natural texture. The leather is uniquely shrunk using special agents–not heat–to retain organic grain and wrinkles. Following an aniline dyeing process, Perlinger's proprietary pigments create deep, vibrant colors, while advanced anti-aging treatment ensures lasting richness that complements the SP4000's enduring beauty, durability, and luxury.
Design Philosophy: "Pierce"
"The force of light that pierces through the darkness."
The SP4000 stands at the pinnacle of Astell&Kern's flagship A&ultima line–a DAP embodying peak performance and design. Like light piercing darkness, the rotating volume wheel generates energy visualized as shards breaking through solid walls. This concept is expressed through sharp edges, restrained detailing, and geometric structures that convey both explosive force and concentrated power.
The interplay of contrasting surfaces and multidimensional forms transcends aesthetics, serving as a visual representation of the SP4000's high-performance audio capabilities. Even the volume wheel's pattern angles have been meticulously crafted to deliver subtle tactile resistance, creating a sensory experience that connects users to the sound itself–not just control, but intuitive, emotional interaction with music.
The choice of materials in the SP4000 perfectly embody both technology and emotion: high-gloss polished 904L stainless steel front paired with PVD-coated ceramic rear, offering exceptional craftsmanship in form and function.
The SP4000 transcends the concept of a digital audio player–it is a work of art where technology, design, intuition, and performance converge, expressing pure passion for the ultimate sound experience.
Features
- 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
What's in the Box?
- Astell&Kern A&ultima SP4000 Digital Audio Player
- Premium Perlinger Shrunken Calf leather case (German craftsmanship)
- USB Type-C charging cable
- Quick start guide and documentation
- Warranty information
Specifications
- Model
- SP4000 (PPF51)
- Body Color
- Black, Silver
- Body Material
- Stainless Steel 904L
- Display
- 6-inch 2K (2160 x 1080) touch screen
- Supported Audio Formats
- WAV, FLAC, WMA, MP3, OGG, APE, AAC, ALAC, AIFF, DFF, DSF
- Sample Rate
-
PCM: 8kHz ~ 768kHz (8/16/24/32 bits 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 (No Load)
- CPU
- Octa-core
- DAC
- AKM4191 x4 + AKM4499EX x4 (Real Quad DAC)
- Decoding Support
- Up to 32bit / 768kHz Bit-to-Bit Playback
- Input
- USB Type-C (for charging & PC/MAC)
- Outputs
-
Unbalanced Out (3.5mm), Optical Out (3.5mm),
Balanced Out (4.4mm, 5-pole only) - Wi-Fi
- 802.11 a/b/g/n/ac (2.4/5GHz)
- Bluetooth
- V5.0 (A2DP, AVRCP, aptX™ HD, LDAC, LHDC, SBC, AAC)
- Dimensions
- 3.34” (85mm) [W] x 5.89” (149.8mm) [H] x 0.76” (19.5mm) [D]
- Weight
- Approx. 21.7oz (615g)
- Feature Enhancements
- Firmware upgrade supported (OTA)
- Operating Temperature
- 0℃ ~ +40℃ (32℉ ~ 104℉)
- Frequency Response
-
±0.006dB (20Hz~20kHz) Unbalanced │ Balanced
±0.06dB (20Hz~70kHz) Unbalanced │ Balanced - S/N
- 129dB @ 1kHz, Unbalanced │ 131dB @ 1kHz, Balanced
- Crosstalk
- -136dB @ 1kHz, Unbalanced │ -145dB @ 1kHz, Balanced
- THD+N
- 0.0005% @ 1kHz, Unbalanced │ 0.0003% @ 1kHz, Balanced
- IMD SMPTE
- 0.0004% (800Hz/10kHz 4:1), Unbalanced │ Balanced
- Output Impedance
- Unbalanced 3.5mm: 0.7Ω │ Balanced 4.4mm: 1.7Ω
- Clock Source
-
Clock Jitter: 25pS (Typ)
Reference Clock Jitter: 200 Femtoseconds - Storage Capacity
- Built -in Memory 256GB NAND
- External Memory
- microSD x1 (Max. 1.5TB)
- Battery
-
Capacity: 6,780mAh 3.8V Li-Polymer
Charge Time: About 4 hours (QC3.0)
Playback Time: About 10 hours (FLAC, 16bit, 44.1kHz, Vol.50, LCD Off) - Supported OS
- Windows 10/11 (32/64bit), macOS X 10.7+
- Additional Notes
-
Audio measurements are based on Normal mode.
Auto Mute is not used during testing. - Price
- $3,900