1. Introduction

This manual provides detailed instructions for the proper use and maintenance of your S.M.S.L D400 PRO High Resolution USB DAC. Please read this manual thoroughly before operating the device to ensure optimal performance and longevity. The S.M.S.L D400 PRO is a high-performance Digital-to-Analog Converter designed for audiophiles, featuring advanced AK449EX+AK4191EQ chips, MQA decoding, XMOS XU-316 USB interface, and support for DSD512 and PCM 32bit/768kHz audio formats.

2. Safety Information

• Do not disassemble the unit. Refer all servicing to qualified personnel.
• Do not expose the unit to rain or moisture.
• Avoid placing the unit near heat sources or in direct sunlight.
• Ensure proper ventilation around the unit.
• Use only the specified power adapter.
• Keep the unit away from strong magnetic fields.

3. Package Contents

Please check that all items are present in the package:

• S.M.S.L D400 PRO USB DAC
• Remote Control
• USB Cable
• Power Cable
• Bluetooth Antenna
• User Manual (this document)

4. Product Overview

4.1 Front Panel

Figure 4.1: Front view of the S.M.S.L D400 PRO, showing the display and control knob.

The front panel features a high-resolution display that shows current input, sample rate, and volume level. A multi-function knob allows for navigation through menus and volume adjustment.

4.2 Rear Panel

Figure 4.2: Rear view of the S.M.S.L D400 PRO, displaying various input and output ports.

The rear panel provides a comprehensive array of input and output options for versatile connectivity with various audio systems.

4.3 Labeled Diagram and Dimensions

Figure 4.3: Detailed diagram of the S.M.S.L D400 PRO with labeled components and dimensions.

The diagram above illustrates the key components and their locations on the device, along with its physical dimensions for placement planning.

1. Knob: Multi-function control for volume and menu navigation.
2. Remote Window: Infrared receiver for the remote control.
3. Indicator Light: Status indicator.
4. Display: Shows operational information.
5. XLR Output: Balanced analog audio output.
6. Bluetooth Antenna: Connection point for the Bluetooth antenna.
7. RCA Output: Unbalanced analog audio output.
8. AES/EBU Input: Professional digital audio input.
9. Coaxial Input: Digital audio input.
10. Optical Input: Digital audio input.
11. USB Input: USB-B input for computer connection.
12. I2S Input: High-performance digital audio input.
13. AC IN: Power input (AC 100-240V).

5. Key Features

The S.M.S.L D400 PRO incorporates advanced technologies to deliver exceptional audio performance:

• Flagship DAC Chips: Utilizes AK4191EQ and AK4499EX for high-fidelity digital-to-analog conversion.
• High-Resolution Display: Features a fully laminated tempered glass display panel for clear information display.
• Advanced Bluetooth Connectivity: Equipped with a high-end Qualcomm Bluetooth chip supporting LDAC (24bit/96kHz), aptX/HD, SBC, and AAC codecs.
• XMOS XU-316 USB Interface: Provides robust and high-performance USB audio processing.
• MQA Support: Full MQA and MQA-CD decoding capabilities.
• High Sampling Rates: Supports DSD512 and PCM up to 32bit/768kHz.
• Multiple Digital Filters: Offers up to 7 digital filter modes for PCM signals.
• Remote Control: Includes a full-function remote control for convenient operation.
• User-Upgradable Firmware: Allows users to update the device firmware.

5.1 Feature Highlights

Figure 5.1: Overview of key technical features including Hi-Res Audio, MQA, DAC chips, distortion levels, op-amps, XMOS, DSD, PCM, filters, remote, and firmware upgrade.

5.2 Core Technologies

Figure 5.2: The S.M.S.L D400 PRO highlighting the AK4499EX and AK4191EQ DAC chips.

Figure 5.3: Close-up view of the AKM DAC chips on the circuit board.

Figure 5.4: Close-up view of the XMOS XU-316 USB processor chip.

Figure 5.5: Illustration of the D400 PRO's high-end Bluetooth chip supporting various codecs.

Figure 5.6: Explanation of MQA full decoding and MQA-CD support, including a comparison of audio waveforms.

6. Setup Guide

6.1 Power Connection

1. Connect the supplied power cable to the AC IN port (13) on the rear panel.
2. Plug the other end of the power cable into a suitable AC power outlet (100-240V).

6.2 Bluetooth Antenna Installation

1. Screw the provided Bluetooth antenna onto the Bluetooth Antenna connector (6) on the rear panel.
2. Ensure the antenna is securely fastened for optimal Bluetooth signal reception.

6.3 Audio Input Connections

Connect your audio source to one of the following input ports:

• USB Input (11): Connect to a computer using a USB-B cable. Install necessary drivers if prompted by your operating system.
• Optical Input (10): Connect to a digital audio source (e.g., CD player, TV) using an optical fiber cable.
• Coaxial Input (9): Connect to a digital audio source using a coaxial cable.
• I2S Input (12): Connect to compatible I2S audio sources for high-performance digital audio transmission.
• AES/EBU Input (8): Connect to professional digital audio sources using an AES/EBU cable.
• Bluetooth: Refer to Section 7.4 for Bluetooth pairing instructions.

6.4 Audio Output Connections

Connect the D400 PRO to your amplifier or active speakers:

• XLR Output (5): For balanced audio connection, use XLR cables to connect to an amplifier with XLR inputs.
• RCA Output (7): For unbalanced audio connection, use RCA cables to connect to an amplifier with RCA inputs.

7. Operation

7.1 Power On/Off

After connecting the power cable, the unit will enter standby mode. Press the power button on the remote control or the multi-function knob (1) to power on the device. Press again to return to standby.

7.2 Input Selection

Rotate the multi-function knob (1) to cycle through available input sources (USB, Optical, Coaxial, I2S, AES, Bluetooth). The selected input will be displayed on the screen (4).

7.3 Volume Control

Rotate the multi-function knob (1) to adjust the output volume. The volume level is displayed on the screen. Alternatively, use the volume up/down buttons on the remote control.

7.4 Bluetooth Pairing

1. Select "Bluetooth" as the input source using the multi-function knob or remote.
2. On your mobile device or computer, search for Bluetooth devices.
3. Select "S.M.S.L D400 PRO" from the list of available devices to pair.
4. Once paired, audio from your device will be streamed to the D400 PRO.

7.5 Menu Navigation

Press the multi-function knob (1) to enter the main menu. Rotate the knob to navigate through menu options (e.g., Digital Filters, Output Mode, Display Brightness). Press the knob again to select an option or confirm a setting. Use the remote control's menu buttons for similar functionality.

8. Maintenance

• Cleaning: Use a soft, dry cloth to clean the exterior of the unit. Do not use liquid cleaners or abrasive materials.
• Storage: If storing the unit for an extended period, disconnect it from power and store it in a cool, dry place.
• Firmware Updates: Periodically check the S.M.S.L official website for firmware updates to ensure optimal performance and access to new features. Follow the instructions provided with the firmware update carefully.

9. Troubleshooting

10. Specifications

11. Warranty and Support

The S.M.S.L D400 PRO comes with a 12-month warranty from the date of purchase. This warranty covers manufacturing defects and malfunctions under normal use. Please retain your proof of purchase for warranty claims.

For technical support, troubleshooting assistance, or warranty service, please contact your authorized S.M.S.L dealer or visit the official S.M.S.L website for contact information.

Important: Any unauthorized disassembly or modification of the unit will void the warranty.