1. Introduction
Thank you for choosing the Questyle M18i Max Portable DAC Headphone Amplifier. This device is designed to deliver high-fidelity audio from your mobile phone, PC, or other compatible devices to your headphones or IEMs. This manual provides detailed instructions for setup, operation, maintenance, and troubleshooting to ensure you get the best experience from your M18i Max.
Figure 1: Questyle M18i Max Portable DAC Headphone Amplifier
2. Package Contents
Please check the box for the following items:
- Questyle M18i Max Device
- USB-C to USB-C Cable
- USB-C to USB-A Adapter
- User Manual (this document)
- Warranty Card (may be included)
Figure 2: M18i Max device, USB-C cable, USB-A adapter, and documentation.
3. Device Overview
3.1. Ports and Controls
Figure 3: M18i Max control layout. Features include USB DAC IN Input Interface, Infineon Flagship Microphone, MFB Multi-Function Button, GAIN Gain Switch, Bluetooth & Phone/PC Mode Switch, Volume Up/Down, On/Off button, 3.5mm Standard Headphone Jack, 4.4mm Full Balanced Headphone Interface, and USB-C charging port.
- USB DAC IN Input Interface: Connects to your source device (phone, PC).
- Infineon Flagship Microphone: For voice calls.
- MFB Multi-Function Button: Operable in Bluetooth mode for various functions.
- GAIN Gain Switch: Adjusts output gain (can be set in phone/PC mode).
- Bluetooth & Phone/PC Mode Switch: Toggles between Bluetooth and USB DAC modes.
- Volume Up/Down Buttons: Adjusts audio output level.
- On/Off Button: Powers the device on or off.
- 3.5mm Standard Headphone Jack: Single-ended audio output.
- 4.4mm Full Balanced Headphone Interface: Balanced audio output.
- USB-C Charging Port: For charging the device.
3.2. Internal Components (Exploded View)
Figure 4: Exploded view of M18i Max. Key components include: 1. OLED Display Screen, 2. Patented SIP Current-Mode Amplifier Module, 3. 3.5mm Single-ended Headphone Jack, 4. 4.4mm Balanced Headphone Jack, 5. USB Type-C Charging Port, 6. Torex Precision Power Management System, 7. XMOS USB DAC, 8. Asynchronous Clock Architecture, 9. Infineon Flagship Microphone, 10. ESS Flagship USB DAC Decoding Chip ES9219Q x2, 11. MCU Controller, 12. Qualcomm Bluetooth Module, 13. USB Type-C Audio Port.
4. Setup
4.1. Initial Charging
Before first use, it is recommended to fully charge your M18i Max. Connect the device to a USB power adapter (not included) or a computer's USB port using the provided USB-C cable. The device has an 1800mAh battery. A full charge provides approximately 8-10 hours of battery life for Bluetooth use and ~8 hours for USB DAC use.
Figure 5: Battery capacity is 1800mAh, providing approximately 10 hours of use. Bluetooth battery life is 8-10 hours, USB battery life is ~8 hours.
4.2. Connecting to Source Devices (USB DAC Mode)
The M18i Max supports USB DAC functionality with various operating systems:
- Android Phones & Tablets: Requires Android 5.0 or higher. Use a USB-C to USB-C cable. Some Android devices may require enabling OTG (On-The-Go) function in their settings.
- Windows PCs: Supports Windows 10 (version 1803 or higher). For older Windows versions (Win7/8/10 prior to 1703), a driver installation may be required.
- iPhones & iPads: iOS is supported. For Lightning interface devices, an additional Kuangshi LTCO2 Lightning to Type-C adapter cable is required (sold separately).
- macOS Computers: Fully compatible.
Connect the M18i Max to your source device using the appropriate USB-C cable. The device will automatically switch to USB DAC mode or you can select it using the mode switch.
4.3. Connecting via Bluetooth
The M18i Max features Bluetooth 5.4 with support for AAC, SBC, aptX, aptX HD, aptX Adaptive, LDAC, and LE Audio.
- Power on the M18i Max.
- Switch the device to Bluetooth mode using the mode switch.
- On your source device (smartphone, tablet, PC), go to Bluetooth settings and search for available devices.
- Select