Astell&Kern – A&ultima SP4000T

Astell&Kern A&ultima SP4000T

Reimagine Analog Sound

With the Astell&Kern A&ultima SP4000T, Astell&Kern redefines what emotional high-end portable audio can be. Built upon the uncompromising digital platform of the SP4000, the SP4000T merges cutting-edge DAP technology with genuine vacuum tube amplification — creating an experience where digital precision meets the soul of analog sound.

At its core lies one vision: to make analog sound not only heard, but deeply felt.

The SP4000T is not simply another flagship music player. It is Astell&Kern’s uncompromising interpretation of how music should sound on the move — emotional, spacious, deeply immersive, and remarkably lifelike.

Key Features of the Astell&Kern SP4000T

• World’s first DAP with 4 genuine Raytheon JAN6418 vacuum tubes
• Triple Tube Mode: Triode, Ultra Linear & Pentode
• Triple AMP System: Tube, OP AMP & Hybrid AMP
• Up to 54 sound combinations via Tube Current & amplifier tuning
• Dual AK4191EQ + AK4499EX flagship DAC architecture
• High Driving Mode for maximum performance
• Native DSD512 & PCM up to 32-bit / 768kHz
• Android 15 with Full Open App Support
• 6-inch Full HD display
• Dual-antenna Wi-Fi
• Premium stainless steel & copper chassis
• Luxury leather case by Badalassi Carlo

A New Era of True Tube Sound — World’s First Quad Tube DAP

The Astell&Kern SP4000T is the world’s first digital audio player to feature four genuine MIL-Spec Raytheon JAN6418 vacuum tubes.

While authentic tube sound has traditionally been reserved for stationary high-end systems, Astell&Kern brings real tube amplification into a portable form factor through a highly sophisticated channel-separated architecture. Dedicated dual-tube structures independently power the left and right channels — inspired by uncompromising high-end home tube amplifiers.

The result is an extraordinary blend of warmth, texture, depth, and musicality, while preserving precision, control, and resolution.

Through meticulous tube matching, differential circuit design, and advanced noise isolation, the Astell&Kern SP4000T minimizes unwanted artifacts while enhancing the rich harmonic structure vacuum tubes are beloved for — delivering the deepest and most emotionally engaging analog sound ever heard from an Astell&Kern player.

Triple Tube Mode — Three Tube Characters, One Player

The SP4000T is the world’s first DAP featuring Triple Tube Mode, opening entirely new possibilities for personal sound customization.

Depending on your music preference, headphones, or listening mood, choose from three distinct tube characteristics:

Triode Mode — The Purest Tube Expression

Smooth, delicate, and emotionally rich. Vocals breathe with intimacy, while acoustic instruments gain natural warmth and organic texture. Perfect for jazz, vocals, acoustic recordings, and intimate performances.

Ultra Linear Mode — The Art of Balance

A perfect blend of tonal richness and control. Smooth yet authoritative, refined yet powerful — a beautifully balanced signature suitable for virtually every genre.

Pentode Mode — Power and Dynamics

More punch, stronger dynamics, and a more direct presentation. Designed for electronic music, rock, large-scale orchestral works, and listeners seeking maximum energy and impact.

Combined with adjustable amplifier modes and Tube Current settings, the Astell&Kern SP4000T offers up to 54 unique sound combinations — a true analog sound palette for passionate audiophiles.

Triple AMP System — Three Amplifier Worlds in One Device

The exclusive Triple AMP System seamlessly combines the best of analog tube technology and advanced amplification design.

Tube AMP Mode

Experience the full character of true vacuum tubes — warm, holographic, emotional, and beautifully musical.

OP AMP Mode

Maximum precision, extraordinary clarity, expansive staging, and exceptional dynamics — the signature Astell&Kern reference tuning.

Hybrid AMP Mode

The best of both worlds. Freely blend analog warmth with high-resolution detail and dynamic performance to shape the perfect listening experience.

Reference-Class DAC Architecture

At the heart of the Astell&Kern SP4000T lies a fully discrete flagship audio circuit featuring dual AK4191EQ processors paired with dual AK4499EX DACs — AKM’s latest premium DAC platform.

By physically separating digital and analog signal processing, unwanted noise is dramatically reduced, allowing for greater purity, lower distortion, and superior detail retrieval.

The result is an exceptionally spacious, refined, and highly resolving sound signature.

The SP4000T supports Native DSD512 playback and PCM up to 32-bit / 768kHz, delivering uncompromising high-resolution performance.

High Driving Mode — Greater Power, Greater Control

Beloved by audiophiles, High Driving Mode returns with enhanced performance in the SP4000T.

With an expanded OPAMP configuration delivering significantly greater driving power, demanding high-end headphones benefit from stronger dynamics, improved control, deeper bass authority, and even greater sonic density.

Every subtle detail is rendered with exceptional precision and realism.

Proprietary Technologies for Ultimate Sound Quality

The Astell&Kern SP4000T integrates Astell&Kern’s latest proprietary audio technologies:

• ESA (Enhanced Signal Alignment) minimizes group delay for improved timing and sonic coherence
• Advanced DAR reconstructs harmonics and enhances upsampling for more natural playback
• A&K Direct Path (ADP) enables true bit-perfect streaming without Android SRC limitations
• Crossfeed recreates a speaker-like listening experience through headphones
• ReplayGain automatically levels volume differences between tracks

Android 15 & Full Open App Service

Powered by Android 15, the SP4000T offers complete access to streaming platforms through Full Open Android support.

Enjoy uncompromised high-resolution streaming from services such as TIDAL, Qobuz, Apple Music, and more — with the highest possible audio quality.

Thanks to Astell&Kern’s first-ever dual-antenna Wi-Fi design, downloads are faster and connections more stable than ever before.

“Burst” Design Concept — Visualizing Sonic Energy

Inspired by the concept of “Burst”, the Astell&Kern SP4000T visually expresses the explosive energy of music.

Sculptural surfaces, premium materials including stainless steel and copper, and the iconic Astell&Kern volume wheel create a sense of mechanical precision and luxurious craftsmanship.

The softly glowing vacuum tube illumination on the rear further emphasizes the player’s unmistakable analog identity.

Completing the premium experience is an exclusive Italian MINERVA leather case crafted by Badalassi Carlo, included in the box.

What’s in the Box

• Astell&Kern A&ultima SP4000T
• Premium Cognac Leather Case by Badalassi Carlo
• USB-C Cable
• Documentation

 

Technical Specifications

Model	Astell&Kern A&ultima SP4000T
Body Color	Silver, Copper
Body Material	Stainless Steel, Copper
Display	6-inch Full HD Touchscreen (2160 × 1080)
CPU	Octa-Core
DAC	Dual AK4191EQ + Dual AK4499EX
Vacuum Tubes	4 × Raytheon JAN6418 (Quad Tube)
Amplifier Modes	Tube AMP, OP AMP, Hybrid AMP
Tube Modes	Triode, Ultra Linear, Pentode
Output Power	3.5 mm Unbalanced: 4.2Vrms 4.4 mm Balanced: 8Vrms
Outputs	3.5 mm Unbalanced / Optical Out 4.4 mm Balanced (5-pole)
Supported Audio Formats	WAV, FLAC, WMA, MP3, OGG, APE, AAC, ALAC, AIFF, DFF, DSF
PCM Support	Up to 32-bit / 768kHz
DSD Support	Native DSD512
Internal Storage	256GB NAND
Expandable Storage	microSD Card Slot (up to 1.5TB)
Wi-Fi	802.11 a/b/g/n/ac/ax (2.4 / 5GHz)
Bluetooth	Bluetooth 5.2 (A2DP, AVRCP, aptX HD, LDAC, LHDC, SBC, AAC)
Battery Capacity	7,450mAh Li-Polymer
Playback Time	Up to 10 hours
Charging Time	Approx. 5 hours (USB PD 3.0 Fast Charging)
Operating System	Android 15 / Full Open App Service
Supported OS (File Transfer)	Windows 10/11, macOS X 10.7 or later
Dimensions	85.7 × 150 × 19.5 mm
Weight	Approx. 544g
Special Features	Triple Tube Mode, Triple AMP System, High Driving Mode, ESA, Advanced DAR, A&K Direct Path (ADP), ReplayGain, Crossfeed, BT Sink, DAC Filters, Volume LED, Tube LED, Dual Antenna Wi-Fi