Astell&Kern HC4 Brings Balanced and Unbalanced Listening Together

Portable DAC and headphone amplifiers are often defined as much by their practical limitations as by their audio hardware. Astell&Kern’s HC4 addresses several of those limitations directly. It combines balanced and unbalanced headphone outputs, replaces the fixed cable design of earlier models with a detachable connection, and adds UAC 1.0 support for gaming systems. Inside, an AKM AK4493S DAC supports high-resolution PCM and native DSD playback, while a dedicated amplifier circuit and carefully managed power design are intended to make that technology workable in a genuinely pocket-sized product. Priced at $220, the HC4 is designed for listeners who want to use wired headphones with smartphones, computers and other compatible digital sources without moving to a full-size desktop component or a separate digital audio player.

Two headphone outputs make the HC4 more adaptable

The most immediately useful change is the inclusion of both a 3.5mm unbalanced output and a 4.4mm balanced output. Earlier HC-series models divided those options between separate products: the HC3 provided a 3.5mm connection, while the HC2 used a 4.4mm balanced socket. The HC4 brings both formats into a single enclosure.

That choice matters because headphone collections are rarely standardized around one plug. Conventional wired headphones and many earphones continue to use 3.5mm connectors, while an increasing number of enthusiast-oriented models are supplied with, or can accept, balanced 4.4mm cables. Providing both sockets reduces the need for adapters and allows an owner to change headphones without also changing the DAC.

The two outputs also make the HC4 easier to retain as a system evolves. Someone can begin with an existing 3.5mm headphone and later move to a 4.4mm-equipped model without making the DAC obsolete. It is an uncomplicated design decision, but one that gives this small component broader practical value than a single-output dongle.

An AKM DAC in a compact USB design

At the center of the HC4 is the AKM AK4493S digital-to-analog converter. Astell&Kern has previously used AKM technology in its portable digital audio players, but integrating a dedicated DAC chip and suitable amplification into a small USB accessory presents different constraints. The HC4 measures 29.5 x 64.5 x 14.5 mm, so its internal design has to accommodate conversion, amplification and power management in a space intended for portable use.

The AK4493S is specified with improved noise control and lower power consumption, two relevant characteristics for a DAC that operates in close association with a phone or computer. The HC4 supports PCM audio at resolutions up to 32-bit/384kHz and native DSD256. Those capabilities allow it to accept a wide range of high-resolution material without requiring the source software to reduce every file to a more limited format.

Format support alone does not establish audible performance, but it does clarify the HC4’s intended role. This is not simply an adapter for restoring a missing headphone socket. It is built as a dedicated digital audio stage for owners who keep high-resolution files or use playback software capable of delivering those formats.

Dedicated amplification and controlled power use

Astell&Kern uses a dedicated amplifier circuit rather than relying only on amplification integrated into the DAC. That circuit is responsible for supporting stable output through both headphone connections while preserving the HC4’s compact dimensions. Microresistors and miniature capacitors are used to fit the required circuitry into the small enclosure.

The design also includes ultra-small tantalum capacitors of the type used in Astell&Kern’s portable players. Their stated purpose is to control power fluctuations and contribute to stable operation. This is especially relevant in a USB-powered product, where the DAC and amplifier must work within the power available from the connected source.

Astell&Kern’s power-management system is designed to minimize current consumption from that source device. For smartphone use, reducing unnecessary demand is an important usability consideration because the audio accessory shares the phone’s finite battery reserve. No specific battery-life claim is provided, but attention to current management shows that portability has been considered at circuit level rather than only through enclosure size.

Digital Audio Remaster expands the processing options

The HC4 also incorporates Astell&Kern’s Digital Audio Remaster technology, commonly abbreviated to DAR. This processing feature raises the sample rate of the incoming digital signal before conversion. Its inclusion brings a function associated with the company’s dedicated audio players into the smaller USB DAC format.

DAR provides an additional playback option rather than changing the native resolution of the original recording. Owners can use it when they want the HC4 to apply Astell&Kern’s remastering process, while the broad native format support remains relevant for high-resolution PCM and DSD sources. The feature helps distinguish the HC4 from simpler dongles built solely around basic digital conversion and headphone output.

Detachable cables improve compatibility and longevity

A fixed input cable can be a weak point in an otherwise useful portable DAC. The HC4 instead adopts a detachable cable system, allowing the source-side connection to be changed as required. USB Type-C and Lightning cables are included, covering compatible USB-C devices as well as supported Apple hardware with a Lightning port.

This arrangement gives the HC4 a practical advantage for households or individuals using more than one device ecosystem. A listener might connect it to a USB-C smartphone or computer at one time and an iOS device through Lightning at another. The cable can be exchanged without replacing the DAC itself.

A removable cable also separates a frequently handled part from the main electronics. The supplied connection can be replaced independently if needs change, subject to compatible replacement options. For a portable product likely to be packed, unplugged and reconnected regularly, that modularity is a meaningful design improvement over an permanently attached lead.

Useful beyond music playback

Support for USB Audio Class 1.0 broadens the HC4’s role beyond phones and conventional computer audio. UAC 1.0 is included specifically for gaming use cases, enabling operation with compatible gaming systems that may not support the more demanding USB audio modes used for high-resolution playback.

This does not turn the HC4 into a gaming headset interface, and no microphone input is specified. Its relevance is instead for players who want to use wired headphones with a compatible game system through an external DAC and headphone amplifier. The dual 3.5mm and 4.4mm outputs remain useful here because they accommodate a wider range of listening hardware.

The HC4 has also been tested for use with Roon. That detail will interest listeners who organize and play music through a Roon-based system, although it should not be confused with a claim that the HC4 is itself a networked Roon endpoint. It functions as the connected USB DAC within an appropriate playback setup.

Who the Astell&Kern HC4 is for

The HC4 is most suitable for listeners who want to keep using wired headphones across several portable and desktop sources. Its strongest practical case is for someone with a mixture of 3.5mm and balanced 4.4mm headphone cables, because both can be accommodated without adapters or separate DACs. Owners moving between USB-C and Lightning devices may also benefit from the included interchangeable cables.

Its high-resolution PCM and DSD support, AKM converter and DAR processing will be most relevant to users who take an active interest in digital playback formats and software. UAC 1.0 support adds value for those who also want a DAC for compatible gaming hardware, while the compact dimensions make it easier to move the same audio interface between systems.

It may be less appropriate for anyone seeking wireless listening, a self-contained music library or the broader interface of a dedicated digital audio player. Likewise, users who need a microphone input or a larger desktop amplifier should look carefully at their connection requirements. The HC4 is deliberately focused: it is a small, wired DAC and headphone amplifier intended to improve flexibility between digital sources and conventional headphones.

Conclusion

The Astell&Kern HC4’s principal strength is the way it consolidates several useful features into one compact component. Its 3.5mm and balanced 4.4mm outputs support a broad selection of wired headphones, while the detachable USB-C and Lightning cables make it adaptable to different source devices. The AKM AK4493S DAC, support for PCM up to 32-bit/384kHz and native DSD256, dedicated amplifier circuitry and DAR processing give it a more ambitious technical foundation than a basic headphone adapter. UAC 1.0 support further extends its usefulness to compatible gaming systems. At $220, the HC4 is aimed at listeners who value wired portability, high-resolution format support and connection flexibility, but do not need the size or self-contained operation of a full digital audio player.