RAL REX-KEB03 dac headphone amplifier


The RAL REX-KEB03 is a portable headphone amplifier dac that works with just about any source. It is Apple MFI certified so it will work with a direct Lightning cable connection.  

It works with most Android based devices and computers. Windows drivers are required to do high resolution audio above 24bit/96kHz and DSD.

It truly is one of the best "bang for the buck" dac/headphone amp combinations on the market today that includes a fully balanced portable headphone amplifier with a variety of input and output options.

A USB Mini B digital input is also included that enables the DSD128, L-PCM 24bit / 384kHz playback. Optical input is at a max resolution of 24bit / 192kHz playback and it utilizes the Sabre ES9018K2M Dac Chip.

USB Input options:
  • iPhone, iPad, and iPod Lightning, iOS-compatible
  • Xperia Z3, Xperia Z2 Tablet, Xperia Z3 compatible
  • NW-ZX1 / NW-F880 series connection, WALKMAN compatible
  • USB Audio Class2 (High-Speed) connection for Android
  • Windows PC or a Mac, PC / Mac-compatible
Optical Input options:
  • connected to the audio equipment with a Toslink S PDIF digital input
  • works with Astell & Kern, Questyle, Sony PCM-D100 and others


Equipped with a "ES9018K2M" ESS made DAC by Sabre offers the highest in digital conversion.

A fully balanced configuration circuit from Dac to Amp

3 Headphone output connection options. Single ended 3.5mm output , Dual mini 2.5mm balanced outputs, Single balanced TRRS 

Balance headphone connection via BTL circuit

Includes a large-capacity lithium-ion rechargeable battery

Apple iOS compatible Connect to an iPhone, iPad, or iPod via Lightning connection 

REX-KEB03 Digital input Connections

RAL Connections

REX-KEB03 is MFI Apple certified Dac. Which means it will digitally handshake directly with the various Apple Lightning equipped devices such as the iPhone®, iPad®, iPod touch®. No Apple Camera Connection Kit is required. Of course it will also connect to the  the latest smartphones with the Android OS. It is recommended to update your device to Android OS Lollipop. Devices such as Xperia®Z3, personal computers such as Windows®PC or Mac® with a USB connection can also be connected. Devices with a digital Toslink output such as the Astell & Kern, Questyle and other portable players or stationary CD player can also be connected.

When the REX-KEB03 is connected to an Apple device, it is recommended that you use high-resolution playback application such as ONKYO HF Player ( paid version, etc.) or Flac Player. This will allow music playback at the highest native resolution such as DSD128 and L-PCM. Native resolution is played back utilizing these Applications vs downsampling, which is what typically can happen with a lot of smartphones.

The RAL REX-KEB03 will also be shipped with a Xperia connection cable. This is a Sony proprietary cable that is hard to source. Compatible for the following devices: NW-ZX1 / NW-F880 series connection, WALKMAN compatible

By connecting to the NW-ZX1, NW-F880 series device utilizing the SONY WMC-NWH10 USB connection, to the KEB03 you can transfer L-PCM up to 24bit / 192kHz from WALKMAN.

The RAL REX-KEB03 can be mounted to a USB Audio Class2 (High-Speed) Android OS devices via a USB-OTG cable.

USB Audio Class2 (High-Speed) are required with Android devices to transfer higher resolution audio formats. This can vary from Android App to Andriod App. Please check with App's associated website for more information 

Connected to a Windows PC requires a USB Audio driver see below for driver downloads. No drivers are required for Mac OS computers. Mac (OS X 10.6.8 and later) operates with the OS standard USB driver.

See Moon Audio Blog section for more information on connecting portable Dacs to computers. Setting vary from Audio Software Application to Application. We recommend Jriver as your audio playback software suite.


The REX-KEB03 utilizes the Sabre 9018C2M reference Dac chip to do all it's digital to analog conversions. This chip is a high performance 32 bit, 2 channel; Audio D/A converter precisely designed for audiophile critical digital conversion. It is the ESS patented 32-bit HyperStream Dac architecture and Time Domain Jitter eliminator. The digital section delivers 127db and THD+N of -120db. it can handle up to 32bit 384kHz PCM data via I2S from either the USB receiver chip or the Toslink receiver chip. Toslink is limited however to 24bit 192kHz input resolution.

ESSD / A converter to be mounted on the REX-KEB03 it is equipped with a high ESS ES9018 low-power version ESS "ES9018K2M" in the series of evaluation as a converter for high-end audio. High-speed (80MHz) uses the ESS own jitter removal algorithm and a digital filter according to the clock.

2 groups equipped with a high-precision crystal oscillator module 

employs a fully balanced configuration circuit to maximize the power of expression

The body of the REX-KEB03 equipped with two independent high precision crystal oscillator module (22.5792MHz, 24.576MHz). The data inputted from the USB accurately converted to I2S signal and is supplied to the DAC unit. In addition, music data that is output from the DAC, via a fully balanced configuration circuit of the independent left and right up to the headphone output after the I / V conversion, we have to maximize the music itself expressive power.

Headphone output corresponding to the four types of mode Output 2 system equipped with a balance and a single-ended output

REX-KEB03 Headphone Amp

The RAL utilizes a bridge-tied load (BTL) amplifier circuit or what they are calling RAL mode. This is a bridged mono output configuration. It is a form of impedance bridging used mostly by the professional audio market. Two channels of a stereo amplifier are fed the same monaural audio signal, with one channel's electrical polarity reversed. Thus there are 4 amplifier channels in the RAL. The headphone, when connected between the two amplifier outputs, bridges the output terminals. This doubles the available voltage swing at the load compared to a single channel amplifier. The available voltage swing across the load is doubled at the same power supply voltage, but the maximum current output ability of the amplifier remains the same. Consequently operating a pair of existing amplifier channels in bridge mode doubles available power output to the load.The headphone sees twice the impedance since it sees twice the voltage at the same current. The balance headphone output utilizes the Texas Instruments TPA6111 Chips with an analog filter via the TPA6138A chip.

"RAL mode", can be utilized via  2x 2.5mm TR Micro jacks, which RATOC recommends for the balance headphone output. The 2.5mm TRRS has become the standard of Astell & Kern and thus was added out of market popularity. One of the 2.5mm Micro Jacks doubles as a AK connection. We will call "AK compatibility mode".

The single-ended headphone output is via the standard 3.5mm stereo mini-jack.

Windows Driver Instructions

Download Windows Driver

Product Reviews

Help Documents

1)USB input

iPhone, iPad, the iTouch(iPod) Lightning, iOS compatible
REX-KEB03 can be connected via a Lightning cable, by using an Apple MFI certified application that supports high-resolution sound playback (ONKYO HF Player paid version, etc.) The RAL will perform the music playback in the following high-resolution (DSD128 & L-PCM you can play without having to convert the highest 24bit / 384kHz) sound source.

Connect the Xperia Z3, Xperia Z2 Tablet, Xperia Z3 compatible
An Xperia dedicated connection cable is shipped with REX-KEB03. Guests can enjoy a hi-res sound source by connecting the Xperia body and this product directly.

NW-ZX1 / NW-F880 series connection, WALKMAN compatible
The REX-KEB03 will work with the Sony NW-ZX1, NW-F880 series via the USB conversion cable by Sony (part # WMC-NWH10). The following high-resolution can be played (L-PCM up to 24bit / 192kHz)

USB Audio Class2 (High-Speed) connection to be incorporated in Android device, Android-compatible
USB Audio Class2 (High-Speed) mounted Android OS devices via the USB-OTG cable that is connected to the REX-KEB03, it can be regenerated high-resolution sound source stored in the Android terminal. In addition, it is also possible to use the Xperia dedicated cable supplied with the product.

Connected to a Windows PC or a Mac, PC / Mac-compatible
REX-KEB03 is, to connect the camera to your computer with the included with the product USB cable (USB standard A⇔USB Mini-B), Hi-Res as a general USB-DAC (DSD128, L- PCM up to 24bit / 384kHz) to play the sound source can do.
Mac (OS X 10.6.8 and later) operates with the OS standard driver.
It is a Windows PC for offers download the special screwdriver.

⇒ from Here driver download for Windows

2)Optical Input

Connected to the audio equipment with a S / PDIF digital Optical Toslink Input (Such as Astell & Kern)
The REX-KEB03 is compatible with a large number of optical digital output device, and S / PDIF digital [optical] input.

Please do not connect the device to the USB Mini-B input terminal when used in the optical input mode.

Please be careful
If you want to change from the USB  and use optical input mode, you need to power off the unit before making these connections. Then Power back up.

The Default Input mode of this product  once turning ON the power is the optical input mode
For  switching to the USB mode, please check the manual for each mode option.

The USB mini-B input of this product is for audio data input only, you will not be able to charge the built-in rechargeable battery. 

To charge the built-in rechargeable battery, connect the AC adapter of the DC + 5V / 1A ~ 2A to the USB Micro-B input.

The Charging function does not also charge the iPhone / iPad / iPod touch.

Other Notes
Please refer to the general specifications page [USB input mode] for each corresponding model of which can be connected( iPhone / iPad / iPod touch)

To check if the Ral is properly connected to the Apple Device, on the Device go to "Settings" ⇒ "General" ⇒ "information" in the iPhone / iPad. This will show whether the unit has been properly recognized.

DSD Will be converted to PCM 176.4kHz via the WALKMAN app. The Walkman can not output DSD

When connecting to a SONY high resolution audio connection via the USB conversion cable (WMC-NWH10), the battery duration of WALKMAN will be shortened by the specifications of the WALKMAN and WMC-NWH10.

This product is compatible with connection to the Android device equipped with a USB Audio Class2 (High-Speed) Driver. See more info Here.

For specification / details, please contact the manufacturer of each Android device.

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