Cayin RU6 USB Dongle R-2R DAC / Headphone Amp

Cayin RU6

Portable Discrete R2R Resistor Ladder DAC + Headphone Amplifier

R-2R Goes Mobile

Most modern dongle DACs use an off-the-shelf delta-sigma chip implementation. But these days, some music lovers crave the sound only R-2R implementation can provide.

An older technology that’s been making a comeback, R-2R is known to produce rich, realistic, natural sound and can have benefits in spatial awareness and staging. But because this type of design requires expensive high-precision matched resistors (and a lot of them), it’s been prohibitively costly and difficult to miniaturize.

Cayin finally made it happen. RU6 is remarkably compact, portable, and power efficient given its technology, and weighs only 28g.

24-Bit Discrete Ladder Resistor Network

R-2R DACs are based on how each bit of the binary sample represents a certain amount of voltage. It starts with a matched pair of two resistors: the first is ‘R’ and the other is ‘2R’ which has twice the value of R.

To achieve 24-bit R-2R decoding, we need 48 resistors per channel — that’s 96 high-precision resistors for stereo sound, which you’ll find in Cayin RU6.

Cayin has incorporated resistors that are not only compact, but deliver precision and remain stable even as temperature fluctuates.

Two Digital to Analog Modes

Cayin has added a classic NOS/OS or oversampling filter feature for the RU6 so that users can experience the stock sound of the R-2R DAC, with an option to switch on oversampling for additional perceived clarity and smoothness.

Non Oversampling (NOS)

• Maintains the original sampling rate of the source bitstream, with no digital filters or post-processing
• Low phase distortion and jitter
• Musical, natural, organic and coherent sound
  

Oversampling (OS)

• Increases sampling rate (upsampling) through interpolation before digital to analog conversion
• Enhances resolution, reduces noise, and improves anti-aliasing
  
• Impressive details and extension, for a clean and sharp presentation
  

Isolated Boards

To minimize interference, RU6’s circuitry is split into two six-layer PCBs, with digital and analog interfaces installed in separate boards. This safeguards signal integrity, ensuring noise from the digital side won’t bleed into the amplification circuit.

High Resolution

RU6 supports PCM up to 384kHz, and DSD64/128/256.

Discrete Volume Control

To maximize data integrity from the source, Cayin devised their own resistor-based volume control network. This premium feature mimics stepped attenuator volume controls seen on high-end amplifiers. This is the first time that this has been implemented on a portable dongle.

The R-2R DAC circuit is demanding on incoming data integrity. Instead of relying on digital mobile phone volume controls, RU6 allows for 100 steps of volume adjustment using nine segments of resistors and switching relays that maintain the transparent sound of the DAC.

Note, there may be some temporary clicking when volume control or play/pause functions occur.

Control and Connectivity

RU6 features hardware volume buttons for convenient control, which also allows for adjustments via the menus.

The 1-inch OLED display shows playback information and allows for settings to be changed. This includes a high/low gain setting for friendly compatibility with many headphones and IEMs.

You’ll find both 3.5mm and 4.4mm balanced Pentaconn connectors for your headphones and earphones.

Compatibility

Cayin’s discreet R-2R circuitry is
designed to consume low power when compared to other highly integrated
DAC chipsets. Their architecture minimizes power drain from the mobile
source, allowing you to enjoy music for longer without worrying about
rapid smartphone, tablet, or laptop battery drain.

RU6 includes a USB-C to USB-C cable for connecting to Android phones and newer PC / Mac computers. A USB-A adapter is also included for computers with this port. Windows computers will require the free USB 2.0 audio driver to be downloaded from the Cayin website.

For iPhone and iPad users who require a Lightning connector, the special CS-L2C Lightning Cable is available separately for plug-and-play compatibility.