Pre-order available. Delivery July 2026

The Astell&Kern A&ultima SP4000T is a high-end digital audio player (DAP) that combines digital precision with analog tube warmth. As the industry’s first portable player, it uses four vintage vacuum tubes (Raytheon JAN6418 Quad) in a symmetrical dual-tube architecture for the left and right channels to eliminate housing vibrations ("Microphonic Noise") and double the sound.

Additionally, it offers a Triple-AMP System (OP-AMP, Tube-AMP, and Hybrid Mode) as well as a Triple-Tube Mode (Triode, Ultra Linear, Pentode) with up to 54 different sound settings. Technically based on Android 15, it uses separate high-end DACs (AK4191EQ & AK4499EX) and supports native DSD512 as well as 32-bit/768kHz.

Core Features

Industry-First Innovations

• Quad Vacuum Tubes (Raytheon JAN6418): Four extremely sensitive tubes operate in pairs in a mirror-symmetrical, differential configuration. This ensures channel separation like stationary high-end home amplifiers and cancels out noise mutually.

• Triple-Tube Mode: Three tube operating modes fundamentally change the sound character:

  • Triode Mode: Focus on rich harmonic textures, ideal for vocals and gentle reverberation.

  • Ultra-Linear Mode: The perfect balance between triode and pentode – powerful yet gently fading.

  • Pentode Mode: Maximum dynamics and power with direct, powerful sound without long reverberation.

The Triple-AMP System

The player combines the best of both worlds through Astell&Kern’s Teraton Alpha technology:

1. OP-AMP Mode: Extremely low noise, maximum clarity, and enormous spatiality.

2. TUBE-AMP Mode: Authentic, warm, and deep analog sound of real tubes.

3. HYBRID-AMP Mode: A 5-stage adjustable mix of analog warmth and digital resolution.

Technology & Anti-Vibration Architecture

Microphonics Protection (2nd Generation): To prevent noise caused by vibrations in four tubes, a 5-stage protection structure was developed. The tubes sit on flexible PCBs, are spring-mounted with silicone dampers, and are fully enclosed in a housing made of 99.9% pure copper.

• HEXA-Audio Circuit: Complete physical separation of digital and analog signals using two AK4191EQ (digital) and two AK4499EX (analog) processors.

• High Driving Mode: Switches OP-AMPs in horizontal parallel to increase dynamics and detail fidelity without worsening noise (SNR).

• ESA (Enhanced Signal Alignment): Minimizes frequency timing differences (Group Delay), resulting in purer sound reaching the ear.

Connectivity & Comfort

• Operating System: Custom Android 15 with Astell&Kern Direct Path (ADP), which bypasses Android sample rate conversion to ensure bit-perfect, lossless streaming (e.g., via Qobuz Connect or Roon Ready).

• Display & Battery: Large 6-inch Full HD display and USB PD 3.0 fast charging (fully charged in about 5 hours). A new flexible battery protection mode preserves battery life.

• Dual Antenna Design: Doubles the Wi-Fi download speed on the 5 GHz band.

Design & Accessories

• "Burst" Concept: The case design visually represents an explosion of focused energy, centered around the distinctive volume wheel. On the back, the tubes softly glow through a viewing window during operation.

• Premium Leather Case: Included is a case made from vegetable-tanned Italian 'Minerva' leather from the traditional tannery Badalassi Carlo (color: Cognac), featuring a special cutout for the tube LED light.

The Premium Leather Case

The included leather case for the SP4000T is made from "MINERVA" leather by "BADALASSI CARLO"—a renowned leather workshop in the San Miniato district of Florence, Italy.

Badalassi Carlo is a tannery that has been producing leather for over 40 years. It combines traditional Tuscan vegetable tanning methods with the theories and techniques of CARLO BADALASSI, a former professor at a leather school in the Santa Croce region.

Vegetable tanning is an environmentally friendly, slow, and time-intensive leather production process in which hides are tanned exclusively with plant-based tannin extracts. For Badalassi Carlo leather, the Tuscan Vacchetta technique is applied: after the hair is removed from the hide, tallow derived from bovine bone meal is added with plant oils during the tanning process.

Since the workshop focuses more on small batches and high-quality production rather than mass production, it is considered a preferred leather craftsman for renowned brands that place the highest value on material quality.

The case is available in the color "Cognac." It fits the entire device perfectly, offers an ideal fit, and features a patterned cutout on the back that beautifully highlights the warm glow of the tube LEDs.

General Specifications

Audio Specifications

Clock Source

Storage Capacity

Battery