Astell&Kern AK-HC5

Astell&Kern AK-HC5: portable USB-C audio converter

The AK4191EQ and AK4499EX chips, until now reserved for flagship Astell&Kern players such as the SP4000, are making their first appearance in a portable converter cable. The Korean manufacturer condenses its reference design into a 46-gram aluminum housing, featuring an OLED screen and a 150-step volume wheel. Connected via USB-C to a smartphone, computer, or console, this converter includes two headphone outputs: 3.5 mm single-ended and 4.4 mm balanced.

The SP4000’s chips in a converter cable

The AK-HC5 is the first portable USB converter to feature AKM’s AK4191EQ + AK4499EX combination, previously the preserve of Astell&Kern players at the very top of the catalog. The SP4000 uses four of each chip, while the HC5 includes one of each. The principle remains AKM’s approach since its new generation: separating digital processing (AK4191EQ) from analog conversion (AK4499EX) into two distinct components, which reduces interference between the two stages. The result on the HC5: PCM up to 32-bit/768 kHz and native DSD up to DSD512 (22.4 MHz).

An aluminum housing and OLED screen

The machined aluminum body features a satin silver finish and weighs about 46 grams, with dimensions of 32 × 64.3 × 16 mm. It is bulkier than most compact USB converters on the market, and the AK-HC5 does not fit in the standard cases supplied with in-ear monitors, nor in MagSafe mounts for DACs. In return, it includes a 1.62-inch OLED screen, a 150-step volume wheel, and a side configuration button. The screen displays the volume, incoming signal format, active conversion filter, and DAR upsampling status. The wheel allows fine level adjustment, whereas most compact converters make do with two increment buttons. The single button is used to navigate the menu, which requires a few manipulations before becoming intuitive.

High Driving mode and dedicated amplification

Astell&Kern reprises here the High Driving mode introduced in the SP4000: a horizontal OPAMP layout that delivers more usable voltage to the headphone output than a conventional compact converter implementation. Output level reaches 2.5 Vrms single-ended on the 3.5 mm jack and 5 Vrms balanced on the 4.4 mm jack. Enough to comfortably drive the majority of in-ear monitors and dynamic headphones with medium or high sensitivity. The most current-hungry planar headphones, however, will still be better served by a dedicated headphone amplifier. To preserve signal purity against interference coming from the smartphone or source computer, the internal cable is double-shielded (tinned copper conductors followed by additional braided shielding) and the dedicated amplifier carefully manages its PSRR and CMRR power supply noise rejection ratios.

DAR upsampling and conversion filters

The Digital Audio Remaster (DAR) function uses processing derived from the brand’s own players. When activated, it reconstructs the incoming signal at a higher rate, either in PCM 384 kHz or DSD256, using a proprietary algorithm. The aim: to soften digital transitions and achieve a more analog-like rendering, especially with low-resolution files. The HC5 also offers six selectable conversion filters from the menu, previously limited to the brand’s players and desktop converters. Each filter slightly modifies time response and the timbre of transients, allowing the user to adjust the rendering according to the track or headphones used.

USB-C, dual output, and console compatibility

The single input is USB Type-C and supports both UAC 2.0 (smartphones, tablets, computers) and UAC 1.0 (PlayStation consoles, Nintendo Switch). Class selection is done directly from the HC5 menu, without a third-party app. Two headphone outputs sit side by side on the edge: the 3.5 mm single-ended jack for the majority of earphones and headphones on the market, and the 4.4 mm 5-pole balanced jack for high-end models supplied with a balanced cable. Output impedance remains low, at 0.5 ohm on 3.5 mm and 1.1 ohm on 4.4 mm, a sufficiently controlled threshold to drive sensitive multi-driver in-ear monitors without audible coloration. The manufacturer includes two cables in the box, one USB-C to USB-C and one USB-C to Lightning compatible with iPhones equipped with the Apple connector, as well as a Synt3 protective case. Like any battery-free USB converter, the HC5 draws its power from the source device: the OLED screen and active amplification place a greater demand on a smartphone’s battery life than Bluetooth playback.

The HC5 compared with the HC4 and previous models

The HC5 extends a lineup expanded by addition rather than replacement: HC2 (Cirrus Logic), HC3 (ESS), HC4 (AKM AK4493S), and HC5 (AKM AK4191EQ + AK4499EX) coexist in the catalog. The technical leap between HC4 and HC5 remains clear, however. The HC4 used a single AK4493S chip from AKM’s previous generation, whereas the HC5 separates digital and analog into two high-end components. Output level rises from 2 Vrms to 2.5 Vrms single-ended, and from 3 Vrms to 5 Vrms balanced. The HC5 also introduces the OLED screen, the 150-step wheel, and the six conversion filters, elements absent from previous models. This hardware package comes at the cost of greater weight and bulk than previous models: the HC5 weighs 46 g, making it the heaviest in the HC series.

Technical Specifications

Overview

• Audiophile Hi-Fi DAC, satin silver finish
• First USB DAC cable equipped with AK4191EQ + AK4499EX chips, delivering a flagship-level sound signature with an exceptional level of detail and realism
• Astell&Kern audio philosophy and precision engineering in a compact format

Audio architecture

• Dual AKM AK4191EQ + AK4499EX DAC
• Native resolution 32-bit / 768 kHz and DSD512 at 22.4 MHz
• Digital Audio Remaster (DAR): audio upsampling to PCM 384 kHz or DSD256 for more natural playback, with increased clarity and depth
• Ultra-pure signal design: double noise-shielding of the cable and dedicated low-noise amplifier for pure sound, free from interference from any connected device

Amplification

• High Driving mode derived from the SP4000, delivering remarkable output power in a compact format
• Horizontal OPAMP layout providing much higher driving power than conventional portable USB DACs
• Rich dynamics, expansive soundstage, and powerful energy

Audio performance

• Frequency response
  • ± 0.006 dB (20 Hz - 20 kHz), unbalanced and balanced
  • ± 0.06 dB (20 Hz - 70 kHz), unbalanced and balanced
• Signal-to-noise ratio
  • 121 dB at 1 kHz, unbalanced
  • 125 dB at 1 kHz, balanced
• Crosstalk
  • −139 dB at 1 kHz, unbalanced
  • −141 dB at 1 kHz, balanced
• THD+N
  • 0.0005% at 1 kHz, unbalanced
  • 0.0004% at 1 kHz, balanced
• IMD SMPTE (800 Hz / 10 kHz, ratio 4:1)
  • 0.0006% unbalanced
  • 0.0005% balanced
• Output impedance
  • 0.5 ohm on 3.5 mm unbalanced output
  • 1.1 ohm on 4.4 mm balanced output
• Output level (no load)
  • Unbalanced: 2.5 Vrms
  • Balanced: 5 Vrms

Supported formats

• PCM: 8 kHz to 768 kHz (8 / 16 / 24 / 32 bits per sample)
• Native DSD
  • DSD64 (1-bit, 2.8 MHz), stereo
  • DSD128 (1-bit, 5.6 MHz), stereo
  • DSD256 (1-bit, 11.2 MHz), stereo
  • DSD512 (1-bit, 22.4 MHz), stereo

Connectivity

• Input: USB Type-C (compatible with UAC 1.0 and UAC 2.0)
• Headphone outputs
  • 3.5 mm unbalanced
  • 4.4 mm balanced (5 poles only)
• Broad compatibility: smartphones, computers, and consoles

Interface and control

• 1.62” OLED screen
• 150-step volume wheel for precise adjustment
• Clear display of playback information

Construction

• Aluminum body, satin silver finish
• Weight: approximately 46 g
• Dimensions (W × H × D): 32 mm × 64.3 mm × 16 mm

Box contents

• 1 Astell&Kern HC5 DAC and amplifier
• 1 USB-C to USB-C cable
• 1 USB-C to Apple Lightning cable
• 1 Synt3 protective case
• 1 quick start guide
• 1 warranty card