Astell&Kern A&Ultima SP4000 Portable Audio Player

Astell&Kern A&ultima SP4000 – Masterpiece of audiophile innovation

Tradition meets perfection: The new flagship of the A&ultima series

With the A&ultima SP4000, Astell&Kern presents the result of over three years of intensive research, continuous technological development, and uncompromising design. As the latest model in the renowned A&ultima series, the SP4000 even surpasses its legendary predecessor, the SP3000 – a milestone for music lovers, audiophiles, and technology enthusiasts.

Highlights of the A&ultima SP4000 at a glance

Innovative Octa-Audio circuit architecture for maximum sound precision

High Driving Mode for powerful, stable and detailed playback

ESA (Enhanced Signal Alignment) technology to minimize group delays

Ultra Low Noise LDO regulator for an extremely noise-free power supply

Any Layer HDI PCB technology for precise signal processing

99.9% pure copper shielding to prevent electromagnetic interference

Full-fledged Android operating system with bit-perfect streaming

For the first time with Advanced DAR 2.0 (Digital Audio Remaster)

Snapdragon Octa-Core processor & 8 GB RAM for seamless performance

Noble case made of 904L stainless steel – known from the luxury watch industry

6-inch 2K touchscreen, LED display, crossfeed, BT sink & replay gain

Outstanding audio innovation: Octa Audio Circuit Architecture

The SP4000 revolutionizes the soundstage with true 1:1 signal processing : Each AK4191 digital processor is directly coupled to an AK4499EX DAC . This configuration minimizes noise and enables even more precise sound reproduction. Thanks to the new quad DAC architecture, the SP4000 achieves a signal-to-noise ratio of 131 dB – a value that redefines audiophile standards.

High Driving Mode – Powerful sound with depth

With twice as many op amps as the SP3000, the SP4000 delivers a significantly denser and more powerful sound. The High Driving Mode ensures a stable and dynamic sound signature—ideal for high-resolution music with deep bass, clear highs, and rich mids.

Virtually noise-free thanks to Ultra Low Noise LDO regulator

For the first time, a precise LDO regulator , similar to that used in medical devices and 5G technology, is used. This reduces noise by up to 97% and enables particularly clean, unadulterated sound reproduction.

Precise signal routing through Any Layer HDI PCB

The Any Layer HDI circuit board technology used in high-end smartphones enables complex circuit designs in the smallest possible space. Signal loss is effectively minimized – for maximum sound detail and even more vibrant music reproduction.

Fully integrated Android operating system with ADP

Astell&Kern Direct Path (ADP) elegantly circumvents Android's sampling rate conversion (SRC) problem. The result: bit-perfect playback, even when streaming – in previously unattainable audio quality.

Advanced DAR 2.0 – Two-stage sound refinement

The new DAR (Digital Audio Remaster) technology processes music in two phases:

VSE (Virtual Sound Extender) virtually restores lost harmonics.

This is followed by high-precision upsampling.

Conversion rates:

PCM 44.1 kHz? 352.8 kHz , 48 kHz? 384kHz

DSD128/DSD256 depending on the source file
The result: a natural, immersive and emotionally touching sound.

Flagship performance with Snapdragon Octa-Core processor

The Snapdragon 6125 octa-core processor and 8 GB DDR4 RAM ensure rapid loading times, stable performance, and a redesigned, fluid user interface. The system-on-chip configuration reduces heat and digital noise, creating more space for pure audio circuitry.

Elegance in function: New user interface & 2K display

The redesigned UI features emotive, LP-animated navigation and clear, intuitive operation. The 6-inch 2K screen (2180x1080 pixels) allows for comfortable browsing and control—a feast for the eyes and ears.

Incomparable materials: 904L stainless steel & PVD ceramic

The SP4000 is crafted from high-quality 904L stainless steel —an extremely durable material normally found only in luxury watches. The back is made of PVD-coated ceramic —sleek, robust, and unique.

LED status display & crossfeed for a natural listening experience

The LED around the power button indicates the bit depth of the current track. The crossfeed function creates a more natural sound on headphones – through targeted mixing and time delay of the channels.

Wireless freedom & intelligent features

AK File Drop : Wireless file transfer via PC, smartphone or FTP

ReplayGain : Automatic volume adjustment for consistent listening

BT Sink : Stream music wirelessly from your smartphone directly to the SP4000

PD 3.0 fast charging : Fully charged in about 4 hours

Luxury meets craftsmanship: leather case made from German shrunken calf

Each SP4000 comes with a premium leather case made from German shrunken calf by Perlinger Leder – a traditional leather company since 1864. The fine, shrink-finished calfskin structure is enhanced by a special aniline dyeing and offers not only protection but also a touch of timeless elegance.

Design concept “Pierce” – light breaks through darkness

The design of the SP4000 is inspired by energy, light, and precision. The sharp edges and geometric shapes reflect the explosive power of sound. Even the pattern of the volume wheel is ergonomically optimized to create an emotional connection between the user and the music .

Conclusion: Astell&Kern SP4000 – The ultimate digital audio player

The Astell&Kern A&ultima SP4000 is more than just a music player. It is a symbiosis of technology, design, craftsmanship, and audiophile perfection – created for those seeking the very best . Experience sound in its purest form – experience the SP4000.

General specifications

Model : SP4000 (PPF51)

Case color : Black, Silver

Case material : 904L stainless steel

Display : 6-inch 2K touchscreen (2160 × 1080 pixels)

Supported audio formats : WAV, FLAC, WMA, MP3, OGG, APE, AAC, ALAC, AIFF, DFF, DSF

Sampling rates :

PCM : 8 kHz to 768 kHz (8/16/24/32 bits per sample)

DSD (native) :

DSD64 (1bit, 2.8 MHz, stereo)

DSD128 (1bit, 5.6 MHz, stereo)

DSD256 (1bit, 11.2 MHz, stereo)

DSD512 (1bit, 22.4 MHz, stereo)

Output level :

Unbalanced: 4.1 Vrms

Symmetrical: 8.2 Vrms (no load)

Processor : Octa-Core

DAC configuration :

4× AKM4191 + 4× AKM4499EX (true quad DAC architecture)

Decoding support :

Up to 32 bit / 768 kHz bit-to-bit playback

Inputs : USB Type-C (charging, PC & Mac connection)

Outputs :

Unbalanced output (3.5 mm)

Optical output (3.5 mm)

Balanced output (4.4 mm, only 5-pin supported)

WLAN : 802.11 a/b/g/n/ac (2.4 / 5 GHz dual band)

Bluetooth : Version 5.0

Supports A2DP, AVRCP, Qualcomm® aptX™ HD, LDAC, LHDC, SBC, AAC

Dimensions :

Width: 85 mm (3.34')

Height: 149.8 mm (5.89')

Depth: 19.5 mm (0.76')

Weight : approx. 615 g (21.7 oz)

Firmware upgrade : Support via OTA (Over-the-Air)

Operating temperature : 0? to +40? (32? to 104?)

Audio specifications

Frequency response :

±0.006 dB (20 Hz – 20 kHz, unbalanced & balanced)

±0.06 dB (20 Hz – 70 kHz, unbalanced & balanced)

Signal-to-noise ratio (S/N) :

129 dB @ 1 kHz, unbalanced

131 dB @ 1 kHz, balanced

Crosstalk attenuation :

-136 dB @ 1 kHz, unbalanced

-145 dB @ 1 kHz, balanced

Total harmonic distortion (THD+N) :

0.0005% @ 1 kHz, unbalanced

0.0003% @ 1 kHz, symmetrical

Intermodulation distortion (IMD SMPTE) :

0.0004% at 800 Hz / 10 kHz (ratio 4:1), unbalanced and balanced

Output impedance :

3.5 mm unbalanced: 0.7 Ohm

4.4 mm symmetrical: 1.7 ohms

Note: Audio measurements are based on normal mode. Auto-mute was disabled during testing.

Clock specifications

Clock jitter : 25 picoseconds (typical)

Reference clock jitter : 200 femtoseconds

memory

Internal memory : 256 GB NAND

Expandable storage : 1× microSD card slot (up to 1.5 TB)

Battery

Capacity : 6,780 mAh, 3.8V Li-Polymer

Charging time : approx. 4 hours (with Qualcomm QC3.0 fast charging function)

Playback time : approx. 10 hours
(at FLAC, 16 bit, 44.1 kHz, volume 50, display off)

Compatible operating systems

Windows : Windows 10 & 11 (32/64 bit)

Mac : macOS X version 10.7 or later