Astell&Kern A&ultima SP4000 Digital Audio Player

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 lineup 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.

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

Enhanced Signal Processing Capabilities

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.

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.

Enhanced Signal Processing Capabilities

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.

Top-Tier Noise Suppression

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.

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.

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.

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.

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 by Astell&Kern

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.

Newest Flagship Device

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

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

To achieve the goal of the A&ultima series, which is 'to provide the best value that no one can imitate while using the most innovative and uncompromising design and craftsmanship', the SP4000 uses 904L stainless steel material that has never been attempted before in a portable audio player. Using this material has expanded its value from just a digital device to the realm of a luxury good.

904L stainless steel is harder and more difficult to process than general stainless steel requiring significantly more time and effort. However, due to its excellent durability and corrosion resistance, it has a characteristic that does not lose its beauty and is why it is used in expensive luxury watches where perfection in all materials and parts must be pursued with an irreplaceable and wonderful luster. Experience the uncompromising beauty and luxury of the SP4000 produced by Astell&Kern’s experienced craftsmanship.

Specifications