When you make one of the best digital audio players in the world, the follow-up act is always tricky. SP4000 delivered definitive flagship sound, along with a huge step forward in user experience for Astell&Kern, however, that huge step forward also came with some growing pains. Enter SP4000T, a new DAP that takes the core design of SP4000 and adds a tube option, while also looking to further improve and evolve the UI. Can SP4000T both match the sound of SP4000 and improve the experience of using it?
Build and Design
In terms of the core material and visual design, SP4000T keeps very close to the SP4000. You get a similar metal chassis, with angular but smooth lines, and basic physical controls – playback control, volume, and a control lock. The similarities extend to the weight as well, and SP4000T is quite heavy, though it may come in a few grams lighter than the original. The most obvious visual difference is only present in tube or hybrid mode: the tube LEDs on the back that light up one of the vacuum tube sets.
The package is also similar, with the same pack-ins that Astell&Kern typically includes in their high-end players: charge cable, SD card slot cover, a nice selection of screen and rear glass protectors, and a leather case. The case is particularly nice, and I both find the fit more secure than the standard SP4000 case, and like the colors and design more.
Internally, there are two big changes:
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SP4000T replaces the amp section with hybrid tube amplification featuring four JAN6418 vacuum tubes with options for tube, hybrid, or solid state mode.
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While SP4000T uses the same DAC chipset as SP4000, AKM4191 + AKM4499EX, SP4000 uses a quad configuration with 4 of each, SP4000T is a dual configuration with only 2 of each.
User Experience
Outside of the controls for the amplification voicing, SP4000T doesn’t offer much more in terms of obvious new features, but the experience is improved over SP4000 in subtle ways. To start with, SP4000T comes with Android 15 installed out of the box. Now, this is still Astell&Kern’s modified Android, which is redesigned to make the player function primary and the other functions secondary, but you can install any app you like from the official Google Play store, and the compatibility and performance has been improved.
Another notable improvement that might not be immediately apparent is the WiFi. SP4000T adds a second WiFi antenna, improving the range, speed, and connection stability over the SP4000, and it feels like a significant upgrade over Astell&Kern’s other DAPs, where WiFi quality has never been a priority. The battery seems to be somewhat better optimized than SP4000, but this is still going to have a relatively short battery life, with around 10 hours in textbook perfect conditions, and closer to 5 with more typical usage.
Probably the most important user interface element on the device is the tube and amp selection utility. You can choose between fully solid state, fully tube, or “Hybrid” with 5 levels of blending between tube and solid state. In addition, there are three tube timbres available: Triode, Ultra-Linear, and Pentode, each with their own sonic characteristics. On top of that, you also have the tube current level, which helps dial in harder to drive headphones with the tube mode, and increasing the tube current level seems to increase the tonal impact of the tubes.
Sound
Astell&Kern’s flagship players have always had a sound signature that was about 90-95% reference and maybe 5-10% romantic, depending on the exact model. Typically you can expect exquisite detail, excellent imaging, and a wide soundstage, with just a touch of softness in the highs, a little added warmth, and some sweetness in the vocals. SP4000 pushed harder into the reference territory than most of their previous players, and SP4000T pulls the sound further back into the warmer, softer territory.
The exact mix of reference detail and euphonic sonic contours depends on exactly which mode you’re running. In full solid state mode, SP4000T is very similar to the standard SP4000, but with a slight added emphasis on the vocals, and a very small loss in detail. Between the three full tube modes, Triode presents a classic tube sound that delivers stronger note weight and a softer edge, Ultra-Linear opens up the soundstage more while maintaining a bit of softness, and Pentode provides a very clean and detailed, but still somewhat tube-y sound. With the hybrid mode, you get even greater depth, blending the tube timbre of your choice with the solid state sound.
SP4000T does seem to have a little more grunt to it than the original SP4000, and while this isn’t going to be a portable solution for very hard to drive headphones, it does quite well with middle of the road planars like the Meze Empyrean II or HIFIMAN Arya Unveiled and high impedance dynamic drivers. It’s also very comfortable with IEMs, and outside of the most sensitive earphones, like Campfire Andromeda 10, there’s essentially zero noise, even in tube mode.
Comparisons - Cayin N8iii ($3999)
The most obvious comparison point for SP4000T is N8iii. Both are Android based tube DAPs priced around $4000, that use flagship AKM DAC configurations, and provide a range of sonic configuration options around tube voicing and hybrid modes. The differences come from the UI design, and exactly what sort of sound you’re looking for.
In terms of sound, Cayin N8iii using Tube mode with the Classic Timbre offers a level of warmth and smoothness that’s a step beyond what SP4000T provides. If you’re looking purely for the most “tube-y” sound that you can get in a high end DAP, this is definitely the one. N8iii also provides a more complete standard Android installation (though it’s a couple versions behind SP4000T’s Android 15), which some might prefer over Astell&Kern’s more modified version.
SP4000T offers a broader range of sonic options though, with a greater range between pure solid state and pure tube options, and more control. I’d give SP4000T a slightly higher rating in terms of pure detail as well. For the interface, if you plan on using it primarily to playback your personal collection of digital music, SP4000T has the edge, as Astell&Kern’s player software design is the best in the business. Cayin’s is nice as well, and with either device, you can install a third party player like PowerAmp, but Cayin puts the apps and Android system first, while Astell&Kern puts the player first.
The Bottom Line
While SP4000T can’t quite reach the pure stratospheric sonic heights of SP4000, it reaches for those same skies and comes very close. Where it comes short on pure sound quality, it provides a much wider range of sound options, blending tube and solid state while maintaining technical excellence. While I’d still consider N8iii the best option for pure tube lovers, SP4000T exceeds it in a number of ways – and at a lower price. If you want a combination of tubes, technical prowess, and customizability, SP4000T delivers a unique and exciting mix that earns a spot among the top flagship players on the market.
