Astell&Kern has shown off the A&ultima SP4000T, the new flagship of its portable digital audio player (DAP) lineup. As the "T" in the name suggests, the player packs four vacuum tubes inside its body, an ambitious attempt to let you carry the warm sound of a desktop tube amplifier in your pocket. Its global debut is set for High End 2026 in Vienna, Austria, on June 4, 2026.

A Portable Player Built Around Four Vacuum Tubes

The headline feature of the SP4000T is exactly what its name implies: four vacuum tubes mounted inside the chassis. Astell&Kern uses Raytheon JAN6418 compact tubes, and by fitting four of them it aims to recreate the soft, characteristic resonance of a large desktop tube amplifier in a player that fits in the palm of your hand.

What makes it even more interesting is that the tubes can be run in three different operating modes. Triode, Pentode, and Ultra Linear each change how the sound is voiced and how distortion behaves, so you can tune the tonal character to match the track or your personal taste. It is a digital device that still offers the analog pleasure of shaping the sound yourself.

Inside Is a Compact Player Running Android 15

The hardware is closer to a small smartphone than to a simple music player. It runs Android 15 on an octa-core CPU, with 256 GB of internal storage that can be expanded up to 1.5 TB with a microSD card. Even a large hi-res music collection is unlikely to run out of room.

The display is a 6-inch 2K (2160 × 1080) touchscreen, so the handling feels much like a smartphone. For connectivity it supports Wi-Fi 6 (802.11ax, dual-band) and Bluetooth 5.2. It can also be connected to a computer to work as a USB DAC (an external audio conversion device), making it a capable centerpiece for a desktop PC audio setup at home.

A DAC and Hi-Res Support That Anchor the Sound

At the heart of the audio path are two AKM4499EX DACs (the parts that convert digital signals to analog) from Asahi Kasei Microdevices, paired with two AKM4191EQ signal processors, a lavish dual-chip arrangement. Combined with the four vacuum tubes, the goal is to marry digital accuracy with tube-style warmth.

The numbers stand out as well. Frequency response is ±0.006dB from 20Hz to 20kHz and ±0.06dB from 20Hz to 70kHz, essentially flat, with total harmonic distortion (THD) below 0.0006% and a signal-to-noise ratio of 124dB, all figures befitting a top-tier model. Playback support is broad too, handling lossless files up to DSD512 and PCM 768kHz.

Connectivity is comprehensive. Wired output covers both 3.5mm unbalanced and 4.4mm balanced, while wireless support spans the major codecs including LDAC, aptX HD, LHDC, AAC, and SBC. A proprietary VSE (Virtual Sound Extender) feature restores the harmonic content often lost in compressed audio, giving your existing files a richer presentation.

Battery, Build, and the Question of Price

The player carries a 7,450 mAh battery rated for up to 10 hours of continuous playback, with a full charge taking about five hours. Two chassis materials are offered, copper and stainless steel, and the substantial finish is very much in keeping with a flagship device.

As for the all-important price, nothing has been officially announced as of this writing. That said, the existing flagship SP4000 sells for about 4,290 USD (around 690,000 yen), so the SP4000T, positioned above it, is expected to land in an even higher price bracket. This is not a player you pick up on a whim, but for listeners who see real value in the very idea of carrying vacuum tubes wherever they go, it is the ultimate one to own.

※1 USD = 160 JPY (as of June 15, 2026)

Summary

The A&ultima SP4000T is Astell&Kern's new flagship DAP, a bold design that tries to bring desktop-class tube sound into a portable form with four vacuum tubes. It pairs modern high-end features such as Android 15, dual DACs, and DSD512 support with the one-of-a-kind appeal of voicing the sound across three tube modes. The price remains undisclosed, but starting with its global debut at High End 2026 in Vienna, the SP4000T looks set to capture the attention of high-end audio fans.