Cayin RU9 Vacuum Tube Portable DAC and Amp

1. Introduction

Thank you for choosing the Cayin RU9 Vacuum Tube Portable DAC and Amp. This device is designed to deliver high-fidelity audio with the unique characteristics of vacuum tube sound, combined with modern digital-to-analog conversion and amplification technologies. This manual provides essential information for the safe and optimal use of your RU9. Please read it thoroughly before operation.

2. Safety Information

• Do not expose the device to water, moisture, or extreme temperatures.
• Avoid dropping or subjecting the device to strong impacts.
• Do not attempt to disassemble or modify the device. This will void the warranty.
• Use only the specified charging cable and power adapter.
• Prolonged listening at high volume levels may cause permanent hearing damage. Adjust volume to a comfortable level.
• Keep the device away from strong magnetic fields.

3. Package Contents

Verify that all items are present in your package:

• Cayin RU9 DAC Amplifier
• USB-C to USB-C Cable
• User Manual (this document)

4. Product Overview

The Cayin RU9 is a compact and versatile portable DAC and amplifier featuring vacuum tube technology for an enhanced audio experience. It includes multiple sound modes and high-resolution audio support.

Figure 4.1: Front view of the Cayin RU9, showing the display and volume knob.

Figure 4.2: Back view of the Cayin RU9, displaying the model number and regulatory information.

Figure 4.3: Side view of the Cayin RU9, illustrating the power, menu, and timbre selection buttons.

Figure 4.4: Detail of the power mode switch, allowing selection between Battery (BAT), DC, and Dongle modes.

4.1. Controls and Ports

• Volume Knob: Rotates to adjust volume, press to mute/unmute.
• Power Button: Press and hold to power on/off.
• Menu Button: Accesses device settings and options.
• Timbre Button: Cycles through sound customization modes (Classic, Modern, Solid-State).
• USB-C Port: For data connection (to source device) and charging.
• 3.5mm Single-Ended Output: Standard headphone output.
• 4.4mm Balanced Output: High-performance headphone output.

5. Setup

Follow these steps to set up your Cayin RU9:

1. Initial Charging: Connect the RU9 to a power source using the provided USB-C cable. The device will indicate charging status on its display. Ensure the device is fully charged before first use.
2. Connect to Source Device: Use the USB-C cable to connect the RU9 to your smartphone, tablet, or computer. The RU9 will automatically detect the connection.
3. Connect Headphones: Plug your headphones into either the 3.5mm single-ended output or the 4.4mm balanced output, depending on your headphone's connector type.
4. Power On: Press and hold the Power button until the display illuminates.

Figure 5.1: The Cayin RU9 features a magnetic backing for convenient attachment to compatible smartphones or tablets.

6. Operating Instructions

6.1. Power On/Off

• To Power On: Press and hold the Power button for approximately 2 seconds.
• To Power Off: Press and hold the Power button for approximately 3 seconds until the display turns off.

6.2. Volume Control

Rotate the volume knob clockwise to increase volume and counter-clockwise to decrease volume. Press the volume knob once to mute or unmute the audio output.

6.3. Sound Customization (Timbre Modes)

The RU9 offers three distinct sound modes to tailor your listening experience. Press the Timbre button to cycle through these modes:

• Classic Mode: Emphasizes the warm, rich characteristics of vacuum tube amplification.
• Modern Mode: Offers a balanced sound profile with enhanced clarity and detail.
• Solid-State Mode: Provides a clean, analytical sound with precise reproduction, bypassing the tube stage.

Figure 6.1: Diagram illustrating the three selectable timbre modes: Classic, Modern, and Solid-State.

6.4. High-Resolution Audio Support

The RU9 supports various high-resolution audio formats, including PCM up to 768kHz, DSD512, and DoP. The integrated XMOS XU316 USB processor ensures accurate and stable data transmission for these formats.

Figure 6.2: The XMOS XU316 USB processor, responsible for handling high-resolution audio data.

6.5. Dual DAC and Discrete Class A Amplification

The RU9 incorporates an in-house R2R DAC and a fully balanced 4-channel Class A amplification circuit. This design ensures powerful, natural, and clean audio output, capable of delivering up to 730mW.

Figure 6.3: AKM DAC chips, part of the dual DAC architecture for precise digital-to-analog conversion.

7. Maintenance

• Cleaning: Use a soft, dry cloth to clean the exterior of the device. Do not use liquid cleaners or solvents.
• Storage: Store the device in a cool, dry place away from direct sunlight and extreme temperatures.
• Battery Care: To prolong battery life, avoid fully discharging the battery frequently. If storing for an extended period, charge the battery to approximately 50-70%.

8. Troubleshooting

If you encounter issues with your Cayin RU9, refer to the table below for common problems and solutions:

If the problem persists after attempting these solutions, please contact Cayin customer support for further assistance.

9. Specifications

Technical specifications for the Cayin RU9:

10. Warranty and Support

The Cayin RU9 comes with a standard manufacturer's warranty. Please refer to the warranty card included in your package for specific terms and conditions. For technical support, service, or warranty claims, please contact Cayin customer service through their official website or authorized distributors.