Astell&Kern A&Ultima SP4000 | Digital Audio Player

A&K's SP4000 Shatters the Limit Set by the SP3000, Harnessing Advanced Octa Circuitry to Deliver a Purer, More Powerful Sound Experience Digital Audio Player with Snapdragon 6125 Octa-core processor First Astell&Kern Device to Feature Advanced DAR Technology Supports High Driving Mode for delivering premium sound quality Ultra Low Noise LDO Regulator for top-tier noise suppression Minimizes group delay with proprietary ESA (Enhanced Signal Alignment) technology Bloom's Take Astell&Kern has always treated their flagship DAPs as a platform to redefine what’s possible in portable audio and with the SP4000, they’ve done it again. While it may not deliver the same leap forward that the SP3000 brought over the SP2000, the SP4000 feels like a culmination of every innovation that came before it, refined to its absolute limit. The build quality is, as expected from A&K, sublime—equal parts futuristic and artisanal. Yes, it’s massive, yes, it’s heavy, and no, your pockets won’t thank you, but one listen and you’ll forget all that. Under the hood, the Quad-DAC setup, improved DAR processing, and High Driving Mode push its sonic performance into rarified territory. With IEMs or even challenging over-ear headphones, it delivers a vivid, expansive soundstage and a hyper-detailed yet cohesive image that feels more like a live performance than a playback. Functionally, the SP4000 also marks a shift in Astell&Kern’s traditionally closed ecosystem. With Google Play preinstalled and true multitasking finally on board, the SP4000 softens the company’s “walled garden” approach and opens up to modern app use without compromising its player-first experience. In the A&K lineup, the SP4000 doesn’t just sit at the top, it transcends it. While the SP3000 brought the revolution, the SP4000 perfects it. It’s not merely Astell&Kern’s best DAP yet, it’s the DAP to beat. Read our full review. Remarkably Close to 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. Built upon an advanced Octa audio circuit architecture, the SP4000 distills 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. Snapdragon Octa-Core CPU A&ultima SP4000 is equipped with a Snapdragon 6125 Octa-core processor. With its faster system response and a redesigned generation user interface, you can spend less time waiting for the music to load and more time enjoying the incredible sound. Combining with the high-performance CPU with 8GB of DDR4 memory lets SP4000 deliver fast and fluid movement with improved multi-tasking through Android OS. To maximize the efficiency of the circuit and reduce heat, 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). Enhanced Signal Processing with Octa Audio Circuit 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. Advanced Engineering for Unmatched Clarity 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. 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. 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 help stabilize battery voltage and effectively suppress noise, resulting in cleaner, purer sound. Precision Sound with Any Layer HDI PCB To minimize signal loss, 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. Additional Features and Enhancements Sound Design Through DAC Filters 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. 4.5th Generation UI The SP4000 features an upgraded UI that balances both functionality and emotional experience.  A&K's First Full Android OS Integration Astell&Kern has overcome Android OS’s sampling limitation (SRC) through its proprietary customization technology, ADP (Astell&Kern Direct Path). First-Ever Implementation of 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. 99.9% Pure Copper Shield Can For the first time in A&K's lineup, 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. 6-inch 2K Display Experience the SP4000 more conveniently and comfortably with a wide 6-inch, large-screen 2180x1080 2K display.  AK File Drop With the new AK File Drop function in the SP4000, you can freely transfer files wirelessly through a PC, smartphone, or FTP program located on the same network Automatic 'ReplayGain' and Uniform Volume Adjust ReplayGain adjusts sound sources with different volumes to identical levels so you can enjoy your own playlists seamlessly. Wireless Hi-Fi Sound via BT Sink Enjoy playback from an external device (ie. smartphone) in high-quality using the BT Sink function. PD 3.0 Fast Charging Supported 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. Crossfeed Technology 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. Material Innovations 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. Shrunken Calfskin Leather Case The SP4000 comes with a deluxe case crafted from shrunken calf leather sourced from Perlinger in Germany, ensuring a level of style and quality that matches the quality of the device. Specifications Full list of specifications Astell&Kern 1 Year Warranty In the Box A&Ultima SP4000 DAP Premium German leather case USB-C cable Quickstart guide