Questyle M15C Portable USB DAC Headphone Amplifier User Manual

1. Introduction

This manual provides comprehensive instructions for the safe and effective use of your Questyle M15C Portable USB DAC Headphone Amplifier. Please read this manual thoroughly before operating the device and retain it for future reference.

The Questyle M15C is designed to enhance audio quality from various digital sources, including smartphones, personal computers, and laptops. It features advanced decoding capabilities and dual headphone outputs for versatile listening experiences.

2. Product Overview

2.1. Package Contents

Figure 1: The Questyle M15C amplifier shown with its included accessories: a Type-C to Type-C cable and a Type-C to USB-A converter.

• Questyle M15C USB DAC Headphone Amplifier x1
• Type-C to Type-C cable x1
• Type-C to USB-A Converter x1
• User Manual x1

2.2. Device Features

The M15C incorporates several key technologies for high-fidelity audio reproduction:

• Lossless Audio Decoding: Supports PCM from 16Bit/44.1kHz to 32Bit/384kHz and DSD256.
• Dual Outputs: Equipped with 3.5mm single-ended and 4.4mm fully balanced headphone outputs.
• Current Mode Amplification (CMA): Utilizes four CMA engines for enhanced audio performance.
• Manual Gain Adjustment: Allows users to select gain modes based on preferences and headphone characteristics.
• MFi Certified: Ensures high compatibility with iOS devices, along with Harmony OS, Android (5.1+), and Windows (10+) operating systems.
• Low Noise Floor: Designed for clean sound with high signal-to-noise ratio and low distortion.

2.3. Component Identification

Figure 2: Internal components and external features of the Questyle M15C, with numbered labels for identification.

1. Patented SiP Current Mode Amplifier module (Patent No.: US 9,614,483 B2)
2. Frosted aluminum body machined by CNC
3. CP3.0
4. Cirrus Logic DAC CS43198
5. 3.5mm headphone jack
6. 4.4mm balanced headphone jack
7. Gain switch
8. Standard Type-C interface, 3X clock asynchronous transmission
9. USB Controller SA9312L
10. Torex power management system, ensuring the M15C remains cool during extended use.

3. Setup

3.1. Connecting to a Source Device

The Questyle M15C is designed for plug-and-play operation with most compatible devices. No additional drivers are typically required for basic functionality.

Figure 3: The M15C is compatible with various platforms including Android, iOS (iPhone/iPad), Windows, and MacOS.

1. Connect one end of the provided Type-C to Type-C cable to the USB-C port on the M15C.
2. Connect the other end of the Type-C cable to your smartphone, PC, or laptop.
   • For devices with a USB-A port, use the included Type-C to USB-A converter.
   • For iOS devices, ensure you are using an MFi-certified cable or adapter if not directly connecting via USB-C (for newer iPads/iPhones). The M15C itself is MFi certified.
3. Once connected, the M15C will typically be recognized as an external audio device. Select it as your preferred audio output in your device's sound settings.

Figure 4: The M15C connected to an iPhone, demonstrating MFi certified compatibility for Apple devices.

4. Operation

4.1. Connecting Headphones

The M15C offers two headphone output options:

Figure 5: The M15C features both 4.4mm balanced and 3.5mm single-ended headphone outputs, accommodating various headphone types.

• 3.5mm Single-Ended Output: For standard headphones and earphones.
• 4.4mm Fully Balanced Output: For headphones with a balanced connection, offering improved sound separation and power.

Connect your headphones to the appropriate jack on the M15C.

4.2. Gain Adjustment

The M15C features a manual gain adjustment switch to optimize output for different headphones and listening preferences.

Figure 6: The M15C includes a gain switch for manual adjustment, allowing users to select gain modes based on headphone characteristics or personal preference. The image also shows the data status indicator LEDs.

• Use the gain switch (labeled 'Gain' or similar) on the side of the device to toggle between low and high gain modes.
• Low Gain: Recommended for sensitive earphones or headphones to prevent excessive volume and potential distortion.
• High Gain: Suitable for less sensitive or high-impedance headphones that require more power to achieve optimal volume and dynamics.

4.3. Data Status Indicator

The M15C features an LED indicator that provides information about the current audio sampling rate:

• 1x LED on: Indicates a sampling rate ≤ 48kHz.
• 2x LEDs on: Indicates a sampling rate > 48kHz (high-resolution audio).

This indicator helps confirm that your device is receiving and processing high-resolution audio signals when available.

5. Maintenance

To ensure the longevity and optimal performance of your Questyle M15C, follow these maintenance guidelines:

• Cleaning: Use a soft, dry, lint-free cloth to clean the device. Avoid using harsh chemicals, solvents, or abrasive materials.
• Storage: Store the M15C in a cool, dry place away from direct sunlight and extreme temperatures.
• Handling: Handle the device with care. Avoid dropping it or subjecting it to strong impacts.
• Moisture: Keep the device away from water and excessive humidity. If it comes into contact with liquids, disconnect it immediately and allow it to dry completely before reuse.

6. Troubleshooting

If you encounter issues with your Questyle M15C, refer to the following common problems and solutions:

6.1. No Sound Output

• Check Connections: Ensure the M15C is securely connected to both the source device and your headphones.
• Source Device Settings: Verify that the M15C is selected as the primary audio output device in your computer or smartphone's sound settings.
• Volume Levels: Confirm that the volume on both your source device and any connected headphones is not muted or set too low.
• Cable Integrity: Try using a different USB cable to rule out a faulty cable.
• Headphone Compatibility: Ensure your headphones are properly connected to the correct 3.5mm or 4.4mm jack.

6.2. Intermittent Disconnections or Audio Drops

• Secure Connection: Ensure the USB cable is firmly seated in both the M15C and the source device. Loose connections can cause intermittent issues.
• Cable Quality: Use the provided high-quality USB cable. Third-party cables may sometimes cause instability.
• Source Device Port: Try connecting to a different USB port on your computer or a different source device to determine if the issue is with the port.
• Power Management: On some computers, USB power saving settings can cause disconnections. Disable USB selective suspend settings in your operating system's power options.
• Restart Devices: Disconnect the M15C, restart your source device, and then reconnect the M15C.

6.3. Poor Sound Quality or Distortion

• Gain Setting: Adjust the gain switch. If using sensitive headphones, ensure you are on the low gain setting. For high-impedance headphones, high gain might be necessary.
• Source Audio Quality: Ensure the audio files or streaming service you are using are of high quality. The M15C enhances, but cannot create, quality from a poor source.
• Volume Levels: Avoid setting the volume too high on either the source device or the M15C, as this can introduce distortion.
• Interference: Keep the M15C away from other electronic devices that might cause electromagnetic interference.

7. Specifications

8. Warranty and Support

8.1. Warranty Information

Please refer to the warranty card included with your product or visit the official Questyle website for detailed warranty terms and conditions. Warranty coverage typically includes defects in materials and workmanship under normal use.

8.2. Customer Support

For technical assistance, troubleshooting beyond this manual, or warranty inquiries, please contact Questyle customer support through their official website or the contact information provided in your product packaging.

You can also visit the Questyle Store on Amazon for additional product information and resources.