A&ultima SP4000

Built on Legacy, Evolving Perfection
 
  • First Full-Android Flagship with Google Play – SP4000 is the first Astell&Kern player running full Android, enabling direct access to apps like Spotify, TIDAL, and Qobuz—no sideloading required—while preserving bit-perfect playback via AK’s proprietary ADP (Astell&Kern Direct Path) audio engine
  • True Quad‑DAC Octa-Circuit Architecture – Uses a 1:1 pairing of four AK4191 digital processors with four AK4499EX DACs (a real Quad-DAC implementation). This architecture dramatically improves signal separation and delivers an exceptional 131 dB SNR
  • High Driving Mode with Parallel Op-Amps – Featuring twice the number of op-amps in a parallel configuration, it drives demanding headphones and IEMs with power and dynamics—adding punch without increasing noise—much like engaging a four-wheel-drive mode
  • ESA – Enhanced Signal Alignment– Proprietary ESA tech aligns frequency bands to arrive in perfect sync, dramatically reducing group delay and improving clarity, coherence, and imaging
  • Ultra-Low Noise LDO Regulator – Incorporates a high-performance LDO power regulator—borrowed from medical/5G tech—that cuts power supply noise by up to 97%, delivering ultra-clean, interference-free playback
  • Precision Any-Layer HDI PCB & 99.9% Copper Shielding – Utilises smartphone-grade HDI PCB to minimise signal loss, and encloses the audio circuit in a 99.9% pure copper shield can to block EMI/RF noise—offering pristine analogue purity
  • Advanced DAR v2 + VSE Restoration – The upgraded DAR (Digital Audio Remaster) system uses a two-stage process: first Virtual Sound Extender (VSE) restores lost harmonics; then DAR up-samples. The result is richer, more immersive, architecturally accurate sound
Sale price£3,799.00

Colour: Silver
Find a dealer
divider

Built on Legacy, Evolving Perfection

 

The A&ultima SP4000 is Astell&Kern’s newest flagship digital audio player, the result of three years of relentless research and innovation following the development of the SP3000.

As part of the A&ultima series—Astell&Kern’s flagship line-up combining cutting-edge technology and top-tier specifications—the SP4000 surpasses the boundaries set by the SP3000, once regarded as the ultimate reference.

Built upon an advanced Octa audio circuit architecture, the SP4000 distils the purest essence of audio engineering, delivering a sound experience unlike anything before it—refined, powerful, and remarkably close to perfection. Discover the SP4000 and experience sound on an entirely new level.

 

Octa Audio Circuit Architecture

In the SP3000, the digital-to-analog signal processing structure was separated in a 1:2 ratio. With the SP4000, it has evolved into a 1:1 architecture.
This new structure, where one AK4191 digital processor is paired with one AK4499EX DAC, allows digital signals to be delivered precisely to a single DAC without the need to distribute noise, enabling improved signal separation and processing.

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

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.

Proprietary ESA (Enhanced Signal Alignment) technology

The SP4000 features proprietary ESA (Enhanced Signal Alignment) technology, which significantly improves one of audio’s long-standing challenges—group delay. ESA technology aligns frequency signals to arrive more uniformly, minimizing frequency distortion and dramatically enhancing sound clarity and purity.

Ultra Low Noise LDO Regulator

The SP4000 features a newly implemented LDO (Low Dropout) Regulator in its power supply,which reduces noise by up to 97% compared to previous models. LDO Regulators are high-performance components typically used in precision medical devices and 5G communication equipment. They help stabilize battery voltage and effectively suppress noise, resulting in cleaner, purer sound.

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.

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.

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.

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.

Advanced DAR

The SP4000 introduces Advanced DAR, Astell&Kern’s second-generation DAR (Digital Audio Remaster) technology, delivering sound that is even more natural and refined. 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.

High-End Shrunken Calfskin Case

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-honoured 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.

   

Included in the box

 
  • 1x Astell&Kern A&ultima SP4000 player
  • 1x High-End Shrunken Calfskin Case
  • 1x USB-C to USB-C cable (1 metre)
  • 3x screen protectors
  • 1x Quick start guide
SP300T whats in the box
General Specifications
Model
SP4000
Body Color
Black, Silver
Body Material
Stainless Steel 904L
Display
6inch 2K (2160 x 1080) touch screen
Supported Audio Formats
WAV, FLAC, WMA, MP3, OGG, APE, AAC, ALAC, AIFF, DFF, DSF, MQA
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), DSD512(1bit, 22.4MHz) Stereo
Output Level
Unbalanced 4.1Vrms │ Balanced 8.2Vrms (Condition 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 input (for charging & PC & MAC)
Outputs
Unbalanced Out (3.5mm), Optical Out(3.5mm) Balanced Out (2.5mm, only 4-pole supported | 4.4m, only 5-pole supported)
Wi-Fi
802.11 a/b/g/n/ac (2.4/5GHz)
Bluetooth®
V5.0 (A2DP, AVRCP, Qualcomm® aptX™ HD, LDAC, LHDC, SBC, AAC)
Dimensions
3.34” (85mm)[W] x 5.89” (149.8mm)[H] x 0.76” (19.5mm)[D]
Weight
About 21.7oz (615g)
Feature Enhancements
Firmware upgrade supported (OTA: Over-The-Air)
Audio Performance
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
Signal to Noise Ratio
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 Out 3.5mm (0.7ohm) │ Balanced Out 4.4mm(1.7ohm)
Clock Source
Clock Jitter
25ps (Typ)
Reference Clock Jitter
200 Femto Seconds
Battery
Capacity
6,780mAh 3.8V Li-Polymer
Continuous Playback Time
about 10hours (Standard : FLAC, 16bit, 44.1kHz, Vol.50, LCD Off)
Charge Time
about 4hours (QC3.0 Charging)
Storage
Built-in Memory
256GB[NAND]
External Memory
microSD (Max. 2TB) x1
OS
Supported OS
Windows 10,11 (32/64bit) MAC OS X 10.7