Astell&Kern Introduces Its New A&ultima SP4000 Digital Audio Player

Astell&Kern introduces new flagship Digital Audio Player, the A&ultima SP4000...

•       Full Android OS Support – simply download and run your Apps

•       Enhanced Signal Processing with Octa-Audio Circuitry Design

•       High Driving Mode delivers premium sound quality

•       Proprietary Enhanced Signal Alignment (ESA) Technology Minimizes Group Delay

•       Ultra Low Noise LDO Regulator for Top-Tier Noise Suppression

•       Advanced Digital Audio Remaster (DAR) Technology

•       New 4.5 Generation User Interface

•       24bit wireless streaming support via aptX™ Adaptive and LDAC™

•       Luxury-watch grade stainless steel & ceramic design; calf-leather case

Astell&Kern, a global leader in high-resolution audio products and accessories, announces a new flagship digital audio player (DAP), the A&ultima SP4000.  The SP4000 will make its global debut at next week’s High End Munich 2025 event (Hall 1, booth D03). The show will also see previews of two new in-ear monitor designs – the Astell&Kern Luna and XIO, a fresh collaboration with 64 Audio – set to launch later this year.

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.  Built upon an advanced Octa circuit architecture, and with a High Driving mode,  the SP4000 distills the purest essence of audio engineering, delivering a refined yet powerful sound that is remarkably close to perfection.

Peerless performance comes matched with enhanced convenience and usability. The SP4000 is Astell&Kern’s first DAP to run the full Android OS – allowing you to directly download and run your favourite streaming apps – while overcoming Android OS’s sampling limitation through its exclusive Astell&Kern Direct Path (ADP) technology.

The high-design SP4000 is crafted from 904L stainless steel – the same grade used by luxury watch manufacturers, including Rolex – with a PVD-coated ceramic back. It comes with a Perlinger calf-leather case.

The new flagship DAP will go on sale this summer, with pricing to be confirmed. See below for lots more details about the SP4000 and its technical innovation.

Mean while Astell&Kern will also show two new In-Ear monitors (IEMs) at High End Munich that will debut in Q3 2025, when more details and pricing information will be revealed.

 XIO: 64 Audio Collaboration IEM

Astell&Kern is excited to announce XIO, its first collaboration with IEM manufacturer 64 Audio.  Both Astell&Kern and 64 Audio share a deep desire to connect listeners to music with superior sounding products designed to experience sound in the purest form.The new IEM is a 10-driver Universal Fit In-Ear Monitor, featuring a true isobaric cone-to-magnet isobaric driver configuration. This advanced setup delivers exceptional audio fidelity by coupling two diaphragms in a unique arrangement where one cone is directly linked to the magnet assembly, ensuring precise movement and reduced distortion. Housed in a polished 904L stainless steel shell with a black DLC (Diamond-Like Carbon) coating, the monitor combines technical sophistication with a rugged, luxurious finish.

Astell&Kern Luna
Luna is a new IEM developed in-house by Astell&Kern.  Luna features a full range single transducer unipolar micro planar magnetic driver, with a frequency response of 20Hz – 30KHz.  A hi-fi grade silver-coated OCC and copper OCC with 4.4mm balanced plug by Eletech is included.    

The Astell&Kern SP4000 - technical details and specifications

Enhanced Signal Processing Capabilities with Octa Audio Circuit Architecture

This new circuit architecture, where one AK4191 digital processor is paired with one AK4499EX analog DAC, allows digital signals to be delivered precisely to a single DAC without the need to distribute noise, enabling improved signal separation and processing.  Previously, in the SP3000, one AK4191 digital processor was paired with two AK4499EX DACs in a 1:2 ratio.  Through continuous research and innovation in circuit technology, this new 1:1 signal processing architecture found in the SP4000 successfully implements a true Quad DAC — a feat previously considered impossible due to noise and other issues.

Most digital players process digital and analog signals together inside the DAC. However, the SP4000 reduces the noise of the digital signal input by using the AK4191EQ, a separate digital delta-sigma modulator, and then the AK4499EX DAC to process the analog signals separately.  By applying this unique design where digital and analog signal processing is physically separated, it is possible to experience an incredible level of sound that has never been experienced before. 

High Driving Mode for Premium Sound Performance

The SP4000 features two OPAMPs arranged in parallel to deliver richer and more detailed sound.  In a parallel op-amp 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. 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 Enhanced Signal Alignment (ESA) technology

The SP4000 features proprietary ESA technology, which significantly improves one of audio’s long-standing challenges—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 device 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. If group delay varies too much across frequencies, it can affect clarity, imaging, and timing.

The proprietary ESA technology found in the SP4000 aligns frequency signals to arrive more uniformly, minimizing frequency distortion and dramatically enhancing sound clarity and purity.

Ultra Low Noise LDO Regulator for Top-Tier Noise Suppression

A newly implemented LDO (Low Dropout) Regulator is used in the SP4000 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.

Full Android OS Integration

In response to the growing shift toward streaming-based music consumption, Astell&Kern has integrated full Android OS support, including the ability to install any app via the Google Play Store for the first time in one of their players.  Astell&Kern overcomes 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. 

New Advanced Digital Audio Remaster (DAR) Technology

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.

Any Layer HDI PCB Technology

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 designed to block various types of noise and electromagnetic interference that could affect the audio block.  Used for the first time in Astell&Kern's lineup, the 99.9% pure copper Shield Can provides not only exceptional shielding performance but also delivers sound that is clearer and more distinct than ever before.

New 4.5 Generation Graphic User Interface

An upgraded UI in the SP4000 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, featuring simple and unintrusive graphics that focus on usability and intuitiveness. Three key concepts, Edge, Simple, and Sensibility, were used to improve usability and increase clarity with a style unique to AK. The black and red theme colors are chosen to reduce eye fatigue, maximize battery usage and reduce heat generation. 

Perlinger calf-leather 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-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.

24bit wireless streaming support and much more

The player includes 256GB of internal memory with support for microSD cards up to 1.5TB, dual-band 2.4/5Ghz a/b/g/n/ac 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.  A 6” 2160x1080 touch screen provides up to 2K resolution.  The SP4000 supports native playback of high-res PCM music up to 32-bit, 768kHz and DSD512. 

ReplayGain automatically and uniformly adjusts playback volume across different music tracks.  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. 

The SP4000 adds support for both aptX™ Adaptive and LDAC™ codecs to provide audiophiles with multiple options for 24-bit audio playback wirelessly.  BT Sink allows the SP4000 to connect to an external device via Bluetooth, and to function as a Bluetooth DAC. Music from an external device, such as a smartphone can now be played back in high-quality, taking full advantage of the advanced audio innovations found in the SP4000.

Qualcomm QC 3.0 fast charging allows you to charge your DAP faster and more efficiently than previous models, reaching a full charge in about 4 hours, providing continuous playback time of around 10 hours.   

In a headphone environment in which the left and right channels are clearly separated, ear fatigue may increase during prolonged listening.  The Crossfeed setting in the SP4000 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.  This effect provides the headphone user with a sound profile similar to listening to the same music track in a room with full-sized speakers.  Using detailed settings such as Shelf Cutoff, Shelf Gain, and Mixer Level, you can set the level of crossfeed according to your listening preferences.

The SP4000 will add Roon Ready support pending completion of testing and final certification by Roon Labs. 

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