Cayin RU7 discrete 1-bit dongle DAC

The Cayin RU7 is an ultra-portable USB-C dongle DAC built around a fully discrete 1-bit resistor network. It combines native DSD decoding, balanced and single-ended headphone outputs, and a hardware resistor ladder volume control in a compact metal chassis. Designed for phones, tablets, and computers, the RU7 delivers precise digital-to-analog conversion without relying on an integrated DAC chip.

Discrete 1-bit resistor ladder DAC

The RU7 uses a fully-balanced discrete 1-bit DAC built from 128 high-precision thin-film resistors rather than an off-the-shelf DAC chip. Incoming audio is converted to a DSD bitstream and processed through four parallel 1-bit DAC channels. This architecture prioritizes timing accuracy and low noise, helping preserve fine detail and stable channel balance during playback.

User-selectable all-to-DSD processing

All incoming digital audio can be converted to DSD64, DSD128, or DSD256 before reaching the DAC stage. PCM is supported up to 384 kHz, and native DSD is supported from DSD64 through DSD256. Converting everything to a single format simplifies signal handling and allows the discrete DAC stage to operate under consistent conditions.

Parallel balanced headphone amplification

The headphone amplifier stage uses dual amplifiers in parallel to deliver higher current and improved control. The 4.4mm balanced output provides up to 400 mW into 32 ohms, while the 3.5mm single-ended output delivers up to 160 mW into 32 ohms. This allows the RU7 to comfortably drive sensitive IEMs as well as many full-size headphones.

Shared headphone and line output

Both the 3.5mm and 4.4mm outputs can be switched between headphone output and fixed-level line output. Line output bypasses the volume control and provides 1.2 Vrms from the 3.5mm jack and 2.4 Vrms from the 4.4mm jack. This makes it easy to use RU7 as a compact DAC feeding a portable amp, desktop amp, or home audio system.

Discrete resistor ladder volume control

Instead of digital attenuation or conventional analog potentiometers, the RU7 uses a discrete resistor ladder volume control with switching relays. Volume adjustment is divided into three segments across 100 steps, allowing fine control at low listening levels while maintaining signal integrity. Short relay delays during adjustment are normal and intentional.

Low-noise dual-PCB design

The digital and analog sections are separated across two six-layer circuit boards. This physical separation helps prevent clock and DSP noise from bleeding into the amplification stage. The result is a quieter background and more consistent performance when connected to mobile devices.

Low power consumption for mobile use

The discrete DAC and amplifier stages are engineered for efficiency, keeping current draw around 100–110 mA. This allows the RU7 to work reliably with phones, tablets, laptops, and USB-enabled digital audio players without excessive battery drain.

Compact metal chassis with OLED display

The RU7 weighs 0.9 oz (25 g) and measures 2.6 × 0.9 × 0.5 in (66 × 24 × 12 mm). A CNC-machined metal chassis protects the internal circuitry, while a 128 × 64 pixel OLED screen shows playback format, sample rate, and volume level. Physical buttons provide direct volume and menu control.

Bundled magnetic leather case

A handmade magnetic leather case is included for daily carry. The case is custom-fit for the RU7 with precise cutouts and includes two adhesive metal plates for magnetic attachment. It offers added protection without obscuring the display or controls.

Product highlights

• Discrete 1-bit resistor ladder DAC
  
• All-to-DSD conversion with user selection
  
• Balanced 4.4mm and single-ended 3.5mm outputs
  
• Discrete resistor ladder volume control
  
• Shared headphone and line output modes
  
• Low-power design for mobile devices
  
• OLED display with hardware controls

Specs

• DAC architecture: Discrete 1-bit resistor network
  
• Supported formats: PCM up to 384 kHz, DSD64 / DSD128 / DSD256
  
• Headphone output power: 400 mW @ 32 ohms balanced, 160 mW @ 32 ohms single-ended
  
• Line output level: 1.2 Vrms (3.5mm), 2.4 Vrms (4.4mm)
  
• Volume control: 100-step discrete resistor ladder
  
• Display: 128 × 64 OLED
  
• Power draw: approx. 100–110 mA
  
• Weight: 0.9 oz (25 g)
  
• Dimensions: 2.6 × 0.9 × 0.5 in (66 × 24 × 12 mm)

What’s included

• RU7 dongle DAC
  
• USB-C cable
  
• USB-A to USB-C adapter
  
• User manual
  
• Magnetic leather protective case