Astell & Kern A&Norma SR25 MKII Portable Music Player with AK Zero1 In-Ear Monitor Headphones & Protective Case (Black)

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Model: WWSMKIIAKB UPC: 795044296389 Item: 177526

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A&Norma SR25 MKII Portable Music Player with Qualcomm aptX HD

A Pocket Powerhouse

True to the core values of Astell&Kern, high fidelity sound lies at the heart of the SR25 MKII, delivering exceptional audio performance to a diverse range of music lovers. The most distinctive feature of the Astell&Kern A&norma product line is its compact form factor. However, the SR25 MKII offers more detailed sound than its predecessor, allowing the clear expression of each and every instrument and vocal note.  

The SR25 MKII offers more versatile connectivity options with the addition of a 4.4mm balanced output for the first time in an A&norma player, LDAC, as well as Qualcomm® aptX™ HD, which supports and deliver true audiophile sound quality.   

The SR25 MKII keeps everything you love about the SR25 and adds new design features. It will produce the best sound quality anywhere, anytime.


  • The SR25 MKII is a true mass premium product
  • Improved audio quality compared to the SR25
  • Versatile connectivity, with the addition of 4.4mm balanced output support
  • Energy-efficient design resulting in 20 hours of continuous playback
  • Supports two-way Bluetooth and high-definition codecs (Qualcomm® aptX™ HD, LDAC)
  • ReplayGain automatically maintains a constant volume

Multiple Output Options

The SR25 MKII supports a 4.4mm balanced output. With 2.5mm, 3.5mm, and 4.4mm output options, you can connect an even wider variety of devices.

The 4.4mm balanced output provides improved dynamic range and bass response, supports a wide soundstage, offers clear imaging, and captures subtle details in the audio source.

Enjoy your music without worrying about adaptors.

Silver Plating Shield Can

Astell&Kern products apply shield cans so that noise and electromagnetic interference, which occur when the countless parts are in operation, do not affect the audio block.

The SR25 MKII has taken it a step further by applying highly conductive, hyper-pure silver plating on the existing shield cans for perfect shielding that provides excellent audio performance.

Excellent Continuous Playback Time

No need to worry about battery life. The SR25 MKII can play continuously for 20 hours with just one full charge, thanks to its optimized, energy-efficient circuitry.

Enjoy your own personal musical performance anytime, anywhere with the SR25 MKII’s extended playback time and its portability.

Wireless Hi-Fi Sound Through BT Sink

The newly introduced BT Sink function connects the SR25 MKII to an external device via Bluetooth, similar to connecting a smartphone with a BT speaker. Music from an external device, such as a smartphone can now be played back in high-quality on the SR25 MKII using the BT Sink function.

RelpayGain Automatically and Uniformly Adjusts Playback Volume

ReplayGain, which adjusts sound sources with different volumes to an identical level, has been applied. Now, enjoy your own playlists seamlessly through the ReplayGain feature on SR25 MKII.

AK File Drop to enjoy wireless transfers

The new AK File Drop function in the SR25 MKII makes files transfers easier and more convenient. Using AK File Drop, you can freely transfer files wirelessly through a PC, smartphone, or FTP program located on the same network. Music file management is now possible with a cableless, wireless solution.


The A&norma SR25 MKII inherits the overall design identity of the A&norma SR25 model, highlighting the rhythmic freedom of music through the harmonious combination of design elements.

The top and bottom edges of the bezel are angled, giving the impression of a smaller rectangle floating freely inside the chassis. The pattern on the side is designed to draw attention to the volume wheel whilst conveying an impression of sound.

AK Zero1 In-Ear Monitor Headphones

The new standard for hybrid sound

The AK ZERO1 is a brand-new In-Ear Monitor product from Astell&Kern.

Astell&Kern strives to inspire and bring enjoyment to all, through the magnificence of experiencing music as close to the original sound. They worked tirelessly to find ways of helping more people enjoy the pleasure of music and strove to deliver sound as true to analog as possible.

AK ZERO1 is the first model that offers the sounds that only Astell&Kern can provide. Let us introduce the first In-Ear Monitor from Astell&Kern, the long-awaited AK ZERO1.


  • Three Different Types of Drivers
  • Perfectly Harmonized Driver Structure
  • Highest Cross-Over Network Management
  • Acoustic Chamber created using 3D Printed Technology
  • Precise CNC Machined Metal Housing
  • Hi-Fi Grade Pure Silver-Coated OFC Cable
  • Hand Crafted in Japan


ZERO is a number that represents the reference point, and it also means the beginning. Astell&Kern, the global leader in the Hi-Fi portable audio market, introduces the In-Ear Monitor product from the starting point of "ZERO". AK ZERO1 is a new start for Astell&Kern and aims to be the new standard for In-Ear Monitors. By building their experience in IEM manufacture from "ZERO", A&K pushes to make ZERO1 a truly best in class product and a market leader in the Hi-Fi IEM area.

The Hybrid IEM with each driver's AK sound harmoniously distributed

Hybrid IEM AK ZERO1 focuses on combining the sounds of three unique driver technologies into one.

Composed of a Micro Rectangular Planar Dynamic Driver, two BA drivers, and a 5.6 mm Dynamic Driver, the AK ZERO1 harmonizes the characteristics of each driver to deliver the most natural sound to your ears.

An ideal frequency response was created through the Cross Over Network, which is designed based on a thorough understanding of each driver’s parameters. At the same time, each driver is carefully placed in the optimal 3D position, enclosed in specifically designed acoustic chambers manufactured with precise 3D printing technology.

By implementing this, A&K eliminated unnecessary movement and resonance of the drivers to ensure stable performance.

Internal Structure

  • The Micro Rectangular Planar Dynamic Driver is a specially developed driver with highly advanced technology that allows a planar driver, normally a very difficult driver to scale down, to be applied to in-ear monitors.
  • Two BA drivers are made using customer coil parameters and offer crystal-clear vocals with super-low distortion.
  • The 5.6 mm Dynamic Driver has been created through a fully automated, error-free process, ensuring rich, controlled, and deep low frequencies.

Hi-Fi Grade Pure Silver-Coated OFC Cable 4 Core (3.5mm Plug)

The Pure Silver-Coated OFC cable maximizes the performance of the Hybrid IEM AK ZERO1. It has been exquisitely crafted with high-purity silver plating and copper, and the aluminum plugs give it even more class

The MMCX connector provides the best quality, offering long-lasting stable performance.

Made in Japan

The Hybrid IEM AK ZERO1 is meticulously assembled by highly experienced engineers and manufactured through stringent processes to the highest of tolerances in Japan with excellent facilities achieving the highest quality possible.


AK ZERO1's premium sound will open a whole new world that you have never experienced before, elevating you beyond the boundaries of sound. This is symbolized by the bold diagonal line that crosses the product, reflecting the identity of the AK ZERO1. "The Boundary to a New World” This key phrase encompasses the design of the AK ZERO1.

The cut surface created by the character line of the AK ZERO1 shimmers in the light, emphasizing the premium quality of the product. The shape of the AK ZERO1 has been carefully designed and refined along the inner ear canal to fit your ears perfectly. Light bounces off each surface, making the earpieces glisten like jewelry.

SR25 MKII Leather Case (Black)

The Perfect Match

The material selected for this important role was created by Synt3, a world-class manufacturer of polyurethane located in Milan, Italy.

The diverse patterns and colors seen in the new brands developed by Synt3 are consistently regarded as new standards in the industry. Synt3's superb sense of design is always at the forefront of the industry.

Synt3 from Milan

The soft and durable LASKINA® polyurethane fabric made by Synt3 in Italy offers protection against external shocks and scratches while providing excellent grip and a styling look.

The MEMORY material on the case is a polyurethane fabric that mimics the texture of classic, high-end leather, for a luxurious and vibrant look, including natural leather-style creases and shine.



A&Norma SR25 MKII Portable Music Player with Qualcomm aptX HD

  • General
    • Model: SR25 MKII
    • Body Color: Mercury D. Silver
    • Body Material: Aluminum
    • Display: 3.6" HD (720 x 1,280) TFT LCD
    • Supported Audio Formats: WAV, FLAC, WMA, MP3, OGG, APE, AAC, ALAC, AIFF, DFF, DSF, MQA
    • Sample Rate
      • PCM: 8kHz ~ 384kHz (8/16/24/32bits per Sample)
      • DSD Native: DSD64 (1bit 2.8MHz)
      • Stereo/DSD128 (1bit 5.6MHz)
      • Stereo/DSD256 (1bit 11.2MHz)
    • Output Level: Unbalanced 2Vrms / Balanced 4Vrms (Condition No Load)
    • CPU: Quad-Core
    • DAC: Cirrus Logic CS43198 x2 (Dual DAC)
    • Decodin: Support up to 32bit / 384kHz Bit-to-Bit Playback
    • Input: USB Type-C input (for charging PC & MAC)
    • Outputs: Unbalanced Out (3.5mm), Balanced Out (2.5mm, only 4-pole supported | 4.4m, only 5-pole supported)
    • Wi-Fi: 802.11 b/g/n (2.4GHz)
    • Bluetooth: V4.2 (A2DP, AVRCP, Qualcomm aptXTM HD, LDAC)
    • Dimensions (W x H x D): 2.5" x 4.26" x 0.63"
    • Weight: about 0.39 lb
    • Feature Enhancements: Firmware upgrades supported (OTA)
    • Operating Temperature: 0°C ~ + 40°C )32°F ~ 104°F)
  • Audio Performance
    • Frequency Response
      • ±0.014dB (Condition: 20Hz~20kHz) Unbalanced / ±0.011dB (Condition: 20Hz~20kHz) Balanced
      • ±0.10dB (Condition: 20Hz~70kHz) Unbalanced / ±0.12dB (Condition: 20Hz~70kHz) Balanced
    • Signal to Noise Ratio : 122dB @ 1kHz, Unbalanced / 124dB @ 1kHz, Balanced
    • Crosstalk: -138dB @ 1kHz, Unbalanced / -144dB @ 1kHz, Balanced
    • THD+N: 0.0006% @ 1kHz, Unbalanced / 0.0005% @ 1kHz, Balanced
    • IMD SMPTE: 0.0004% 800Hz 10kHz(4:1) Unbalanced / 0.0003% 800Hz 10kHz(4:1) Balanced
    • Output Impedance: Unbalanced Out 3.5mm (1.2ohm) / Balanced out 2.5mm (1.8ohm), (1.7ohm)
  • Clock Source
    • Clock Jitter: 25ps (Typ)
    • Reference Clock Jitter: 70ps
  • Battery
    • Capacity: 3,150mAh 3.7V Li-Polymer Battery
    • Continuous Playback Time: about 20hours (Standard: FLAC, 16bit, 44.1kHz, Unbalanced, Vol.50, EQ Off, LCD Off)
    • Charge Time: about 2.5houra (5V 2A General Charging)
  • Memory
    • Built-in Memory: 64GB (NAND)
    • External Memory: microSD (Max. 1TB) x1
  • OS
    • Supported OS: Windows 8,10 (32/64bit), MAC OS X 10.7, and up

AK Zero1 In-Ear Monitor Headphones

  • General
    • Model: AK ZERO1
    • Drivers
      • Hybrid Drivers
      • Special Micro Rectangular Planar Dynamic Driver x1
      • Custom Balanced Armature Driver x2
      • 5.6mm Micro Dynamic Driver x1
    • Connector: MMCX
    • Housing Material: Aluminum
    • Frequency Response: 25Hz - 30kHz
    • SPL: 96dB@1KHz (1mW)
    • Impedance: 16Ω@1kHz
    • Total Harmonic Distortion: 0.7%@1kHz

SR25 MKII Leather Case (Black)

  • Material: Synt3 LASKINA® polyurethane fabric (Made in Italy)
  • Colors: Black, Denim Blue, Orange

What's in the Box

What's in the Box

A&Norma SR25 MKII Portable Music Player with Qualcomm aptX HD

AK Zero1 In-Ear Monitor Headphones

  • Earbud L/R
  • 3.5mm MMCX Cable x1
  • 5 Pairs of Silicone Ear Tips
  • 1 Pair of Foam Tips
  • Carrying Case x1

SR25 MKII Leather Case (Black)


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