Astell & Kern (A&K) will showcase the SP4000T to the public at the upcoming High End audio show in Vienna, along with a new wired in-ear headphone called Clarus, which features nine drivers per earbud. The SP4000T is a portable digital music player with an onboard tube stage.
Astell & Kern A&ultima SP4000T Quad Valve Player
High End Vienna 2026 is the chosen location for the official launch of the Astell&Kern SP4000T digital audio player, the latest addition to the flagship A&ultima series, and the Clarus in-ear monitors.
The A&ultima SP4000T, which will be available in stainless steel and copper finishes, features a fully discrete circuit architecture that separates digital and analog signal processing, with two AK4499EX DACs and dedicated AK4191EQ processors per channel. According to the manufacturer, this reduces noise and improves clarity, depth, and purity across the entire signal path, while supporting native playback up to 32-bit/768kHz PCM and DSD512.
The new SP4000T DAP from A&K perhaps distinguishes itself most from its competitors by being the first digital music player to feature matching Raytheon JAN6418 MIL-Spec vintage vacuum tubes in a quad configuration, resulting in a dual tube structure for each channel. Furthermore, the SP4000T benefits from an improved second-generation five-stage antimicrophonic architecture that suppresses microphone noise. According to the designers, the Triple Tube Mode in the SP4000T is once again a first for portable audio players, and in combination with the T Series Signature Triple Amp Mode and tube current level adjustment, the company claims to offer up to 54 possible combinations, yielding a highly diverse “analog sound palette.”
There are also three tube sound modes available: the Triode mode is said to emphasize rich harmonics and, by their own account, a lush, sustained warmth, ideal for vocals and acoustic instruments. The Ultra Linear mode, on the other hand, combines the sonic richness of Triode with the power and control of Pentode, resulting in a so-called refined yet authoritative sound suitable for a wide range of music genres. Finally, there is the Pentode mode, which, according to A&K, focuses on maximum output and dynamic impact, preserving the warmth of the tubes while simultaneously delivering a cleaner, more direct, and more energetic reproduction.
The SP4000T features a High Driving Mode with a parallel op-amp configuration for a wider dynamic range, while ESA (Enhanced Signal Alignment) technology minimizes group delay and frequency distortion, and Advanced DAR technology recovers lost harmonics before upsampling for a more natural and lifelike sound.
Astell & Kern’s Teraton Alpha technology is on board for effective noise suppression of audio power sources, distortion-free amplification, and noise prevention of the audio interface. As a result, the four tubes in the configuration and the advanced op-amp design ensure both authentic analog warmth and ultra-high resolution clarity.
The user can choose between the special Op Amp mode for powerful dynamics, a wide range of detail, and low-noise precision, or the Tube Amp mode for the rich, emotional character and natural sound reproduction of tube amplifiers. Thanks to the five-stage Hybrid Amp mode, the listener can combine the strengths of both amplifiers and fine-tune the balance between them to their own taste.
Astell & Kern SP4000T: equipped with Android 15
The Astell&Kern SP4000T runs on Android 15 with full Google Play support, with the understanding that ADP technology (Astell&Kern Direct Path) bypasses standard Android limitations regarding sample rate conversion, enabling truly lossless, bit-perfect playback of streaming services. The new DAP also features Astell&Kern's first dual Wi-Fi antenna design, with internal tests according to the manufacturer showing that the download speed on 5 GHz is up to twice as high as with previous models.
The device also offers 256 GB of internal storage with the option of microSD expansion up to 1.5 TB, and features a 6-inch Full HD touchscreen, dual-band Wi-Fi, DLNA network functionality, USB audio output, and USB DAC functionality for Mac and Windows PCs.
There is also support for aptX Adaptive and LDAC codecs, while BT Sink mode enables the SP4000T to function as a high-quality Bluetooth DAC for external devices such as smartphones. Features such as ReplayGain, AK File Drop wireless transfer, USB PD 3.0 fast charging, and customizable battery protection further enhance ease of daily use.
Available cases
The SP4000T comes in a luxurious cognac brown leather case from Badalassi Carlo. Two additional luxury leather cases will also be available: a black cowhide case from Gruppo Mastrotto and an olive green vegetable-tanned leather case from Badalassi Carlo.
Astell&Kern Clarus: Nine drivers
Clarus is the fourth model in Astell&Kern's IEM series and is made of 6061-T6 aluminum. Most notably, however, Clarus is designed with a tribrid architecture featuring nine drivers. This design is intended to ensure that each driver performs optimally within its specific range.
The result is that a dynamic driver delivers the natural weight and depth of the low frequencies, a precisely tuned array of Balanced Armature (BA) drivers reproduces the details and resolution of the mid- and high frequencies, and the latest MEMS drivers render the higher frequencies with exceptional precision.
Prices and delivery information
The A&K Clarus and SP4000T can be found at the Astell&Kern stand at High End Vienna, which is just around the corner. Prices and delivery information will be announced later.
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