Cayin RU7 1-Bit Resistor Network USB Dongle DAC / Headphone Amp

Cayin RU7

Discrete Resistor Network 1-Bit Dongle DAC + Headphone Amplifier

1-Bit 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 a ladder DAC implementation can provide.

A classic technology that’s been making a comeback, R-2R and 1-Bit are known to produce smooth, 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 with the original RU6, and now, the new RU7.

Fully Balanced Resistor Network

While the DAC of both RU6 and RU7 are resistor-network based, the 96 pieces (2x48) resistor network in RU6 is a stereo (2-ch) R-2R implementation, the 128 pieces (4x32) resistor network in RU7 is a fully balanced 4-ch DAC design. Although we need to convert the DAC output to single-ended for subsequent processing, the fully balanced DAC can render more detail and preserve more dynamics of the music. If we treat R-2R and 1-Bit as two different but equal engineering approaches to convert the digital audio bitstream to the analog waveform, the fully balanced design in RU7 will still be a step up from the singled-end design in RU6.

Parallel Driven Dual Amplifiers

We want to provide an upgrade headphone amplification to as many users as possible with RU7, so we revised the circuit to parallel dual amplifiers, delivering 80% more power when balanced driven with similar overall power consumption.

• Fully Balanced 1-Bit Discrete Resistor Network DAC
  • 1/1000 ultra-high precision TCR25 low-temperature coefficient thin film resistors
  • Native decode DESD64/128/256, support PCM up to 384kHz.
• User-selectable All-to-DSD
  • Users can specify DSD64/128/256 DSD output formats through menu setting
  • Different DSD output settings might sound slightly different and drain more power when a higher-resolution output format is selected.
• 100 steps 3-segment High Precision Resistor Array Volume Control
• Hardware Volume +/- button
• TWO 6-layer PCB, digital and analog circuits on separate boards
• 3.5mm single-ended phone output delivers 160mW per channel at 32Ω loading
• 4.4mm balanced phone output delivers 400mW per channel at 32Ω loading
• Compatible with Android, iOS, macOS, Windows 7/8/8,1/10, and DAP with USB Audio output
• High/Low gain control
• Compact and seamless CNC aluminum chassis with 1” 128x64 OLED screen
• 66mm x 24mm x 12mm, ~25g net weight.
• USB-C to USB-C cable, USB-C to USB-A adapter included
• Green Leather case included
• Optional USB-C to Lightning cable CS-L2C (sold separately)