Astell&Kern A&ultima SP4000 – The New Standard in Flagship Portable Audio
The A&ultima SP4000 is Astell&Kern’s most advanced digital audio player to date—crafted after three years of continuous innovation since the landmark SP3000. It redefines what’s possible in portable high-resolution playback, delivering a sound that’s refined, powerful, and remarkably true to the original recording. From its advanced circuitry to its luxurious design, the SP4000 is engineered to exceed the expectations of the most discerning audiophiles.
Enhanced Signal Processing with Octa Audio Architecture
At the heart of the SP4000 is a revolutionary new signal design: a 1:1 pairing of AK4191 digital processors and AK4499EX DACs, forming a true Quad DAC architecture. This configuration eliminates noise-causing signal splitting and achieves a new level of separation and clarity. By processing digital and analog signals independently—with the AK4191EQ handling digital modulation and the AK4499EX dedicated to analog conversion—the SP4000 minimizes interference and delivers sound that is detailed, pure, and deeply immersive.
High Driving Mode – Power Meets Precision
Utilizing a parallel OPAMP configuration, the SP4000 expands its driving power without raising the noise floor, ensuring higher dynamic range and stunning detail retrieval. This High Driving Mode delivers a stable, confident output—capable of driving even demanding headphones with authority—while preserving nuance and emotional impact across all genres.
ESA Technology – Group Delay, Solved
Astell&Kern’s proprietary Enhanced Signal Alignment (ESA) technology addresses the long-standing issue of group delay by ensuring that all frequency signals arrive in perfect sync. This dramatically improves timing, stereo imaging, and clarity, offering a listening experience that feels immediate, lifelike, and coherent.
Ultra Low Noise LDO Regulator
A newly designed Low Dropout (LDO) Regulator reduces power-related noise by up to 97% over previous models. Borrowed from high-precision medical and 5G tech, this advanced component ensures maximum voltage stability and near-silent operation—paving the way for unparalleled sound purity.
Advanced DAR & VSE – Digitally Refined, Emotionally Real
The second-generation DAR (Digital Audio Remaster) system debuts in the SP4000, featuring a two-step enhancement process. First, Virtual Sound Extender (VSE) restores lost harmonics and natural texture. Then, the DAR engine performs high-precision upsampling for a more refined output. Together, they deliver sound that is organic, engaging, and remarkably faithful to the source.
Full Android OS with Bit-Perfect Streaming
For the first time, an Astell&Kern player supports the Google Play Store, offering seamless access to your favorite streaming apps. A&K’s Direct Path (ADP) technology bypasses Android’s SRC limitations, ensuring bit-perfect, lossless playback—even while streaming—so you never compromise on sound quality.
Premium Build, Inside and Out
• Any Layer HDI PCB: Enables compact, high-density circuitry with minimal signal loss
• 99.9% Pure Copper Shield Can: Exceptional electromagnetic shielding for ultra-clean audio
• 6” 2160×1080 Full HD Display: Sharp, vibrant UI with improved battery efficiency
All-New 4.5 Generation UI – Intuitive Meets Beautiful
The redesigned interface brings music to life with an elegant LP-style album browser and the signature Crimson Theme. Built on the principles of Edge, Simple, and Sensibility, the UI blends visual clarity with user comfort, reducing eye strain while elevating the emotional connection to your music.
Luxury Leather Case by Perlinger, Germany
Each SP4000 comes with a premium case made from Shrunken Calf leather by Perlinger, a legendary German tannery established in 1864. Using a chrome tanning and shrinking process—not heat—the leather retains its rich grain and texture. Finished with aniline dyes and Perlinger’s proprietary pigments, the case offers exceptional durability, vibrant color, and timeless style to match the SP4000’s sophistication.
Specs & Features at a Glance
• Storage: 256GB internal + microSD card support up to 1.5TB
• Wi-Fi: Dual-band 2.4/5GHz (802.11 a/b/g/n/ac)
• Connectivity: USB-C, USB DAC functionality, DLNA, USB Audio Out
• Screen: 6.0” 2160×1080 Full HD touchscreen
• Playback Support: PCM up to 32-bit/768kHz & native DSD512
• ReplayGain: Auto volume adjustment across tracks
• Wireless File Transfer: With AK File Drop over your network
• Bluetooth: Supports aptX™ Adaptive and LDAC™
• BT Sink Mode: Use the SP4000 as a Bluetooth DAC for external sources
• Battery Life: Approx. 10 hours of continuous playback
• Charging: Qualcomm QC 3.0 Fast Charging (full charge in ~4 hours)
• Crossfeed Feature: Customize stereo imaging for headphone listening
• Roon Ready: Pending final certification from Roon Labs
The A&ultima SP4000 is more than a digital audio player—it’s a master-crafted listening instrument, combining leading-edge innovation with luxurious design and audiophile-grade performance. Whether you’re streaming, collecting, or critical listening, the SP4000 sets the new reference in portable high-end sound.
Deutsch
Markus –
The SP4000 is a statement. What Astell&Kern has achieved here shows one thing very clearly: after the already outstanding SP3000, they have not stopped thinking about the “mobile high-end DAP” concept. In terms of sound, the player is at the absolute top level – thanks to the AK4191/4499EX combination with real separation of the digital and analog paths – and that for each individual channel – everything seems even tidier, more spacious and more engaging than with the SP3000. Plus the new High Drive mode: even demanding and problematic over-ears are controlled with ease, without compromise.
I find the ESA technology particularly exciting – finally someone is seriously addressing the group delay problem. The result is an incredibly precise and clear, but never sterile sound flow.
Most people will be pleased with the more open Android system: it is finally possible to install any apps via the Playstore. This not only expands the possibilities, but also extends the upgrade cycles, as there is no longer a whitelist.
Design, workmanship, the new Crimson interface – as always, it’s all very well thought out and elegant, but never ostentatious. For me, the SP4000 is currently THE digital audio player par excellence, a real high-end technology gem for the very best sound enjoyment.