Astell&Kern SP4000T Tube DAP and Clarus IEMs Head to High End Vienna 2026 as Wired Audio Fights Back

Astell&Kern is bringing the A&ultima SP4000T Vacuum Tube DAP and Clarus In-Ear Monitor to High End Vienna 2026, and the timing feels right. The Vienna show opens June 4 at the Austria Center, just as wired IEMs are enjoying one of their strongest runs in years. CanJam NYC 2026 made that hard to miss, with in-ear monitors and portable audio electronics pulling heavy traffic from listeners who have not surrendered the 4.4mm balanced cable to the Bluetooth empire just yet. 

A&K has earned some goodwill from us recently. The A&ultima SP3000T showed that a tube-equipped DAP could be more than a glowing party trick, while the SP3000 impressed with its resolution, timbre, and natural presentation. The SP4000T and Clarus now give Astell&Kern an opportunity to show whether its next portable flagship pairing can deliver the kind of wired listening experience that has personal audio buzzing again.

The A&ultima SP4000T

The A&ultima SP4000T gives Astell&Kern a new flagship tube DAP by combining modern digital audio processing with a more traditional analog output stage. The headline feature is its use of four RAYTHEON JAN6418 MIL-Spec vintage vacuum tubes in a quad configuration, making it the first portable digital audio player to use that tube arrangement. It is the kind of spec that will get the portable audio crowd leaning forward, assuming they have not already spent the rent money on cables and IEMs.

Raytheon Tubes Inside the SP4000T

The SP4000T uses an independent dual tube structure with four tubes in total, divided between the left and right channels. That type of channel separated tube design is more commonly associated with home audio tube amplifiers than portable digital audio players.

Each tube is measured for noise and gain characteristics before matching. Astell&Kern says the tube section is isolated through independent modular flexible PCBs and a multi layered internal architecture, which is important in a portable design where noise, heat, vibration, and consistency are all factors.

The SP4000T also introduces Triple Tube Mode, which Astell&Kern describes as a first for the DAP category. Combined with the company’s T Series Signature Triple AMP Mode and adjustable Tube Current settings, the player offers up to 54 possible sound combinations.

Astell&Kern offers three tube modes on the SP4000T. Triode Mode is intended to emphasize harmonic richness, warmth, and a more rounded presentation. Pentode Mode is designed for higher output and stronger dynamic impact while retaining tube character. Ultra Linear Mode sits between the two, balancing the tonal weight of Triode Mode with the control and drive of Pentode Mode.

The larger goal is to combine Astell&Kern’s TERATON ALPHA platform, quad vacuum tube architecture, and OP AMP design in a portable player that can deliver high resolution digital playback with adjustable analog tube character.

Amplifier Mode Support

The SP4000T gives listeners three amplifier options. OP AMP Mode uses the player’s solid state output stage and is intended to deliver lower noise, stronger control, and a more direct presentation. TUBE AMP Mode routes playback through the vacuum tube section for listeners who prefer a warmer tonal balance and a more spacious presentation.

HYBRID AMP Mode blends the OP AMP and tube stages across five selectable levels, allowing users to adjust how much tube character is added to the signal. The goal is to give listeners more control over the SP4000T’s output character without requiring external hardware or EQ.

Noise Suppression

The SP4000T introduces an upgraded 5-stage second-generation Anti-Microphonic Architecture (up from the previous 4-stage design) to suppress microphonic noise (noise generated in vacuum tubes from even the most minor external vibrations).

Streaming and Wi-Fi

The SP4000T runs Android 15 and includes Google Play Store support, giving users broader access to streaming apps than earlier closed-platform DAPs. To preserve playback quality, Astell&Kern uses its ADP, or Astell&Kern Direct Path, technology to bypass Android’s standard sample rate conversion. That allows compatible streaming services to deliver lossless, bit-perfect playback through the player rather than being forced through Android’s normal audio path.

The SP4000T also introduces Astell&Kern’s first dual Wi-Fi antenna design. The goal is faster and more stable wireless streaming and downloads, especially on 5GHz networks. According to Astell&Kern’s internal testing, the new design can deliver up to twice the 5GHz download speed of previous models, although real-world performance will still depend on network conditions, router quality, and distance from the access point.

DACs and Processing

The SP4000T uses a discrete circuit architecture that separates digital and analog signal processing. Its DAC section is built around dual AKM AK4499EX DACs and dedicated AK4191EQ processors for each channel, a layout intended to reduce noise and preserve signal integrity across the playback chain.

Based on Astell&Kern’s SP4000 platform, the SP4000T also includes High Driving Mode, which uses a parallel OP AMP configuration to increase output capability and improve control with more demanding IEMs and headphones.

Astell&Kern’s ESA, or Enhanced Signal Alignment, technology is included to improve timing accuracy across the frequency range. The goal is cleaner imaging, better clarity, and a more stable soundstage. The SP4000T also includes DAR, or Digital Audio Remaster, which applies upsampling to PCM and DSD files with the aim of improving perceived detail and harmonic texture.

Additional internal refinements include Any Layer HDI PCB technology and a 99.9% pure copper shield, both used to reduce signal loss, noise, and electromagnetic interference inside the player.

Connectivity and Display

The SP4000T includes 256GB of internal storage, with microSD expansion up to 1.5TB. It supports native playback up to 32-bit/768kHz PCM and DSD512, giving it the file compatibility expected from Astell&Kern’s flagship DAP lineup.

The player uses a 6-inch Full HD touchscreen and supports dual-band Wi-Fi, DLNA networking, USB audio output, and USB DAC operation with Mac and Windows computers.

Bluetooth support includes aptX Adaptive and LDAC, giving users higher-quality wireless options when a cable is not practical. BT Sink mode also allows the SP4000T to receive Bluetooth audio from an external device, such as a smartphone, and function as a portable Bluetooth DAC.

Other usability features include ReplayGain, AK File Drop for wireless file transfers, USB PD 3.0 fast charging, and customizable battery protection settings.

Crossfeed

For extended listening comfort, the SP4000T includes advanced Crossfeed controls that recreate a more speaker-like listening experience through headphones, allowing users to fine-tune spatial presentation and reduce listening fatigue over long sessions.

Packaging

The SP4000T is packaged with a premium leather “Cognac’ colored case crafted using ‘MINERVA’ leather from ‘BADALASSI CARLO‘, a renowned leather workshop located in the San Miniato district of Florence, Italy.

Two additional premium leather cases will be available for the SP4000T. A black case, crafted from soft cowhide by GRUPPO MASTROTTO, delivers an exceptionally soft touch, with a uniform surface quality and a distinctively vibrant Italian colouration. An olive-coloured case, crafted from premium vegetable-tanned leather by BADALASSI CARLO, is crafted through a proprietary tanning and dyeing process. Both cases feature a standing mechanism on the back to provide greater convenience in use.

Astell&Kern Clarus IEM

In addition to the SP4000T, Astell&Kern will show its Clarus IEMs for the first time at High End Vienna 2026.

Clarus is the fourth model in Astell&Kern’s IEM series, developed around the company’s goal of delivering a transparent, low distortion presentation for high resolution portable listening.

The Clarus uses a new 9-driver Tribrid architecture. Each side combines dynamic, balanced armature, and MEMS drivers, with each driver assigned to its own frequency range rather than being asked to cover too much of the spectrum. The shells are crafted from premium grade 6061-T6 aluminum, a material chosen for its rigidity, durability, and ability to support a more stable acoustic structure.

The technical goal is a more controlled full range presentation, with bass handled by the dynamic driver, midrange and treble detail managed by the BA drivers, and the most delicate high frequency information reproduced by the MEMS drivers. In theory, that division of labor should help Clarus deliver stronger separation, cleaner imaging, and a more open sense of space without forcing one driver type to do all of the heavy lifting.

The Bottom Line

The SP4000T is not the first DAP to use vacuum tubes, and Cayin’s N8iii is an important reminder that Astell&Kern is not operating in an empty lane. What makes the SP4000T different is the combination of four Raytheon JAN6418 MIL-Spec tubes in a quad configuration, three selectable tube modes, hybrid amp control, Android 15 with Google Play Store support, and A&K’s flagship DAC and processing platform in one portable player.

It is too early to judge the sound, but Astell&Kern did not build its reputation in the DAP category by making timid moves. The SP4000T looks like a deliberate attempt to bridge high resolution digital playback with adjustable analog tube character. The real question is whether analog focused listeners will hear this as meaningful engineering or another very expensive pocket-sized argument for staying up too late with IEMs.

Price & Availability

The Astell&Kern SP4000T and Clarus will make their global debut at the High End Show, 4–7 June at booth HX4, M04, Austria Center Vienna.

Pricing and availability for the SP4000T in Stainless Steel and Copper editions will be announced shortly.

Clarus will be available for demo in the Astell&Kern booth at High End Vienna 2026. Pricing, availability, and further details will be confirmed in due course.

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