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Astell&Kern A&ultima SP4000 Copper
Astell&Kern is one of the most recognisable brands in the high-resolution portable player segment. The company built its reputation on advanced Android-based digital audio players designed to combine high sound quality with support for streaming services and a distinctive angular industrial design. The A&ultima line serves as the manufacturer's flagship series, where its most sophisticated technical solutions typically make their debut, including complex DAC configurations, elaborate headphone amplification stages and proprietary technologies intended to improve signal processing and reduce noise. Limited editions of these players have long attracted particular attention, and because copper is a material that carries strong positive associations in the hi-fi world, the standard A&ultima SP4000 is now joined by a special A&ultima SP4000 Copper version. According to the manufacturer, copper has been used not only for visual impact but also as a component intended to influence the sonic character directly. The new model is aimed at listeners who treat a portable player as a fully fledged high-end source in any listening environment.
SP4000 Copper is based on the same platform as the regular SP4000 but replaces the stainless steel enclosure with a chassis made from 99.98% pure copper. This material offers excellent conductivity and shielding properties, although it is considerably more demanding to machine, which is why Astell&Kern emphasises that the enclosure requires a multi-stage stabilisation process together with precise polishing and finishing to ensure durability and resistance to oxidation. According to the manufacturer, copper's natural conductivity and shielding characteristics help protect sensitive audio circuits from interference, contributing to deeper and more authoritative bass, a rich and clearly articulated midrange and treble with a smooth, natural decay. The result is intended to be a coherent and realistic presentation that remains neutral while also expressive and engaging.
At the heart of SP4000 Copper is the same Octa Audio 1:1 architecture developed for the standard SP4000, in which each AK4499EX DAC is paired with a dedicated AK4191 processor. This creates a true quad-DAC configuration with precise channel separation and a signal-to-noise ratio reaching 131 dB according to the manufacturer. The headphone amplifier uses a new parallel operational amplifier arrangement that increases output power and current delivery without raising the noise floor. The design also incorporates the proprietary ESA technology to minimise group delay, together with the Advanced DAR digital remastering system that adds harmonic reconstruction and precise upsampling for a more natural presentation of recordings. The player supports PCM files up to 32-bit/768 kHz and DSD up to DSD512, while several selectable DAC filters allow users to tailor the processing characteristics to their preferences.
The manufacturer also highlights the redesigned power section. A new ultra-low-noise LDO regulator is said to reduce battery-related interference by up to 97% compared with earlier designs, while multilayer Any Layer HDI circuit boards allow signal paths to be routed efficiently within a compact footprint while maintaining strong isolation between circuit sections. The player is equipped with a 6780 mAh battery providing up to 10 hours of playback and supports fast charging via the Power Delivery 3.0 standard. System responsiveness is handled by an octa-core Snapdragon 6125 processor supported by 8 GB of RAM, which together with the updated user interface is intended to ensure smooth app performance and quick system reactions.
SP4000 Copper runs on Android with Astell&Kern's full system integration, allowing bit-perfect playback even within streaming applications through the company's ADP solution. Users have access to 256 GB of internal storage together with a microSD slot supporting expansion by up to 1.5 TB. Wireless connectivity includes dual-band 2.4 and 5 GHz Wi-Fi as well as Bluetooth with aptX Adaptive and LDAC support, while built-in DLNA functionality makes it easier to integrate the player into a home audio network. The 3.5 mm single-ended and 4.4 mm balanced outputs allow compatibility with a wide range of headphones, and the USB-C port supports data transfer, charging and operation as an external DAC for macOS and Windows computers.
In everyday use SP4000 Copper closely follows the established A&ultima design language, but stands out through its warm copper finish and faceted chassis intended to improve grip and emphasise the technical character of the device. A 6-inch 2K touchscreen on the front displays track information, active functions and player settings. The package is completed by a Perlinger leather case made from Shrunken Calf leather, designed to protect the copper enclosure from scratches while reinforcing the limited edition's premium character. Astell&Kern A&ultima SP4000 Copper is available in a limited number of units, with a suggested retail price of £3,999/$4,499/€4,699. Info and photos by Astell&Kern.
