Astell&Kern A&ultima SP4000T Portable Tube Audio Player

RAYTHEON JAN6418 Quad: A New Standard in Tube Configuration

The SP4000T uses independent dual-tube structures for the left and right channels, a channel-separated design once found only in high-end home tube amplifiers. The four tubes work in a mirror-symmetric differential configuration, so music is amplified with greater clarity while common-mode noise cancels out. Each tube is measured for noise and gain before pairing, then isolated on independent modular flexible PCBs.

Triple Tube Mode

Triode mode brings out the richest harmonic texture and lingering reverb. Ultra Linear blends Triode tone with Pentode output for a balanced sound across every genre. Pentode maximises output and dynamic range for a clean, powerful presentation. Tube Mode applies in Tube AMP and Hybrid AMP modes.

Triple AMP System

Built on Astell&Kern's TERATON ALPHA technology, the SP4000T offers Tube AMP mode for authentic tube warmth, OP AMP mode for Astell&Kern's signature clarity and soundstage, and a five-stage Hybrid AMP mode that blends the two to your taste.

2nd Generation Anti-Microphonic Architecture

A five-stage structure suppresses microphonic noise: a separate modular flexible PCB, a silicone base cushion, custom-fit silicone tubing around the tube leads, a silicone damper suspending each tube, and a copper shield can over the whole assembly. While in Tube or Hybrid mode, the tubes glow softly through the rear window.

HEXA Audio Circuit

Dual AK4499EX DACs are paired with dedicated AK4191EQ delta-sigma modulators for each channel. The digital signal is cleaned by the AK4191EQ before passing to the fully isolated analog DAC, giving complete physical separation of digital and analog signal paths.

High Driving Mode, ESA and Advanced DAR

High Driving Mode uses parallel OPAMPs for greater driving power without added noise. ESA minimises group delay so all frequencies arrive more uniformly. Advanced DAR first restores lost harmonics with VSE, then upsamples for a fuller, more natural sound.

SP4000T Copper Edition

The Copper Edition is machined from high-purity (99.98%+) copper with a multi-layer coating that prevents oxidation and discolouration. Copper's conductivity and electromagnetic shielding protect the signal, while its natural resonance adds depth to the warm harmonics of the four vacuum tubes.

Streaming and Convenience

Full open Android 15 with bit-perfect Astell&Kern Direct Path playback, Roon Ready and Qobuz Connect support, BT Sink, a dual-antenna Wi-Fi design with around twice the 5GHz download speed of the previous model, USB PD 3.0 fast charging, 7 DAC filters, Crossfeed, ReplayGain and a bit-depth indicator LED around the power button.

Premium Leather Case

The bundled case is made from vegetable-tanned Minerva leather by Badalassi Carlo of Florence, Italy. It comes in Cognac and has a rear cutout that shows off the tube glow.