The portable audio world often moves at a glacial pace compared to smartphones or laptops, and for good reason. When you’re catering to golden-eared audiophiles willing to drop thousands on pocket-sized music players, every circuit and component choice matters, and they’re not looking to update quite as often. That’s why Korean audio stalwart Astell&Kern typically takes years between flagship releases, and why their new A&ultima SP4000 digital audio player represents such a significant milestone. After three years of development following their SP3000, the company has finally embraced full Android while doubling down on the premium materials and circuit innovations that hardcore music enthusiasts demand.
OCTA EVOLUTION
Audiophiles understand that DAP design isn’t just about specifications but the device’s architecture. As such, the SP4000 introduces an entirely reimagined Octa audio circuit that takes a fundamentally different approach than its predecessor. Where the SP3000 paired a single AK4191 digital processor with two AK4499EX DACs, the SP4000 opts for a cleaner 1:1 signal path. Dedicating one digital processor to one analog DAC, A&K shifts its audio philosophy almost completely, eliminating the noise inherent in signal distribution, resulting in dramatically improved separation and spatial imaging that simply wasn’t possible with the previous design.
The implementation of dual OPAMPs arranged in parallel provides what they’ve dubbed “High Driving Mode,” a clever way to boost dynamic range expansion without introducing the additional noise normally associated with increased amplification. This arrangement delivers a richer, more powerful sound signature. Think of it as the audio equivalent of switching from two-wheel to four-wheel drive, providing the extra power needed to navigate sonic terrain with more confidence.
ANDROID UNLEASHED
Perhaps the most significant upgrade isn’t about audio at all but how the user is able to interact with the device. After years of resisting, A&K has finally implemented full Android OS support, making the SP4000 their first flagship player that lets users directly download streaming apps through the Google Play Store. The days of sideloading APKs are officially over.
But introducing Android has its own potential challenges, particularly with sample rate conversion that can degrade audio quality. However, A&K addresses this through their proprietary ADP (Astell&Kern Direct Path) technology, which delivers lossless playback even when streaming.
FLAGSHIP LEGACY
Since launching their first high-resolution player at CES 2013, Astell&Kern has consistently pushed boundaries in portable audio. The name itself – combining “Astell” (Greek for “star”) and “Kern” (German for “core”) – reflects their mission to reach the core of music reproduction. The A&ultima line has been their flagship series, with each iteration setting new benchmarks for top-shelf portable audio.
Fans of the SP series understand its dedication got innovation, from the SP1000 in 2017 that established the series’ premium credentials, to the SP2000T in 2021 that innovated with vacuum tube amplification, to the groundbreaking SP3000 in 2022 with its world-first independent dual audio circuitry. And with the SP4000, Astell&Kern continues their tradition of delivering technology while building on everything they’ve learned in previous iterations.
LUXURY CRAFTSMANSHIP
Like a luxury timepiece, the SP4000 makes its statement through the materials used. Finished in either black or silver, the frame is crafted from top-tier 904L stainless steel paired with a PVD-coated ceramic back. Aside from appearing luxurious in your hand, these materials were chosen specifically for their superior vibration-damping properties.
For the luxurious carrying case, A&K tapped Perlinger, the historic German leather artisans. It features supple calf leather treated through a proprietary cold-shrinking technique. This method, unlike traditional heat treatments, maintains the hide’s natural texture patterns while allowing Perlinger’s signature coloring process to achieve a depth and vibrancy that should develop a beautiful patina over time.
SPEC SHEET
Model: Astell&Kern A&ultima SP4000
Display: 6″ touch screen (2160×1080 resolution)
Processor: Octa circuit architecture (AK4191 digital processor + AK4499EX DAC)
Storage: 256GB internal + microSD support up to 1.5TB
Connectivity: Dual-band Wi-Fi, DLNA networking, USB-C, USB DAC mode, Bluetooth
Audio Support: Native playback up to 32-bit/768kHz PCM and DSD512
Battery: About 10 hours playback
Materials: 904L stainless steel frame, ceramic back
Operating System: Custom Android with Google Play Store support
PRICING & AVAILABILITY
Available this summer, the A&ultima SP4000 from Astell&Kern is yet to have a price tag attached. However, you can expect it to exceed the $3,699 price tag of the previous SP3000 model.
Recap
Astell&Kern A&ultima SP4000
After 3 years of R&D, Astell&Kern has debuted its A&ultima SP4000, now with Android compatibility and improved audio structure.
