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.
AK4191EQ x4
AK4499EX x4
Octa-Core
High Driving
Mode
Independent
ESA
Android OS
Advanced
DAR
The A&ultima SP4000 Copper Limited Edition goes beyond a high-end portable audio
player. It
represents the culmination of Astell&Kern’s expertise in material engineering, precision
manufacturing, and refined analog sound design.
SP4000 Copper is the brand’s most definitive answer to a single question: how far can we go in
the pursuit of the ultimate sound?
Copper is theoretically one of the most ideal materials for audio, yet among the most difficult
to use in real products. Its exceptional electrical conductivity and superior electromagnetic
shielding minimize even the finest signal loss, but its rapid oxidation and low surface
stability make practical application extremely challenging.
In portable devices, which are constantly exposed to temperature changes and external
environments, copper becomes an even greater risk. Rather than avoiding this challenge,
Astell&Kern confronted it directly, applying an advanced multi-layer coating process that
requires high technical expertise to ensure the long-term stability of 99.98% pure copper.
The exterior, too, is never design for design’s sake. High-purity copper is highly
susceptible to minute
deformation during machining, yet Astell&Kern’s accumulated expertise enables precise control down to
the finest tolerances. Through this process, the SP4000 Copper is realized not as a mass-produced
device, but as a beautifully finished high-end audio object.
Most importantly, the sound is the culmination of this relentless craftsmanship. Free from exaggeration
or coloration, it delivers the texture and weight of instruments, the pace and breath of performance,
rendered as an exceptionally refined expression of the original sound—enhanced by the inherent
characteristics of copper.
Deep, authoritative bass, a dense and articulate midrange, and treble that fades naturally come together
as a single, cohesive flow, allowing emotion to be fully revealed through sound. Beyond simply “great
sound,” it offers an experience where the true value of the original recording is faithfully realized.
The SP4000 Copper Limited Edition embodies Astell&Kern’s unwavering commitment to surpassing limits
without compromise. Created for those who truly understand the essence of pure sound, SP4000 Copper sets
a new standard for what high-end audio can be.
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.
[ Signal Separation Processing - 1:2 Structure ]
[ Signal separation processing - 1:1 structure ]
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.
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.
The driving range expands horizontally, with no increase in noise or reduction in SNR. This results in increased dynamic range and enhanced sound detail.
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.
[ Without ESA ]
[ With ESA ]
*What is Group Delay?
In audio, group delay refers to the time differences it takes for various frequencies to pass through an
internal system. In other words, each frequency reaches the output at slightly different times. Simply put,
it describes a phenomenon where different frequencies within an audio signal do not arrive simultaneously,
resulting in slight delays.
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.
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.
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 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.
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.
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.
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.
Clean, angular lines echo the physical design of the device, seamlessly blending its identity into the screen for a striking, edge-defined aesthetic.
Despite its wide range of features, the interface is designed to be intuitive and user-friendly. Graphics are kept simple and unobtrusive, allowing users to focus entirely on the current screen without distraction.
Motion effects enhance emotional engagement and improve user interaction.
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.
With the SP4000, you can enjoy the fun of creating your own sound style by directly selecting various DAC filters provided by the DAC manufacturer. Design your own sound through 6 DAC filters.
Super Slow Roll-off
No echo reproduces
Short Delay Slow Roll-off
Minimal echo reproduces
Slow Roll-off
Minimal echo reproduces
Low dispersion
Short echo reproduces
Short Delay Sharp Roll-off
Post echo enhances
Sharp Roll-off
Pre and post echoes makeThe LED light surrounding the power button provides information on the Bit Depth of the currently playing song, and also adds a visually pleasing element by making it shine and stand out.
* The LED light can be turned on or off according to user settings.
16bit
24bit
32bit
DSD
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.
Experience the SP4000 more conveniently and comfortably with a wide 6-inch, large-screen 2160x1080 2K display.
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 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.
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.
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.
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.
‘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 that embodies the
peak of
performance and design. Like the The force of light that pierces through the darkness, the rotating volume
wheel generates energy that is visualized as shards breaking through a solid wall. This imagery is captured
through sharp edges, restrained detailing, and geometric structures, expressing both explosive force and
concentrated power. The interplay of contrasting surfaces and multidimensional forms goes beyond aesthetics,
serving as a visual representation of the SP4000’s high-performance audio capabilities. Even the angle of
the volume wheel's patterns has been meticulously crafted to deliver subtle tactile resistance, offering a
sensory experience that connects users to the sound itself. It's not just about control—it’s an intuitive,
emotional interaction with music.
The choice of materials in the SP4000 perfectly embodies both technology and emotion. The front features
high-gloss polished 904L stainless steel, while the rear is finished with PVD-coated ceramic, offering
exceptional craftsmanship in both form and function.
The SP4000 is more than just a digital audio player—it is a work of art where technology, design, intuition,
and performance converge, expressing a pure passion for the ultimate sound experience.
