Resolving the trade-offs between size, power consumption, and audio performance is a top priority for battery-powered compact portable devices. The M18i comes with two patented quad-core Current Mode Amplifier SiP modules, designed by Questyle Technology. The amplifier provides powerful drive with delicate timbre, while once again establishing a new ultra-low distortion record at 0.0002%. Current Mode Amplification (CMA) technology is combined with TOREX's high-efficiency power management system to give the M18i low power consumption despite its high performance. The M18i comes with the latest ESS flagship ES9219Q DAC chip. Questyle and ESS engineers worked together to develop the TTA DAC framework to take the performance of M18i to the limit of what's physically possible.

The M18i provides both 3.5mm unbalanced and 4.4mm balanced outputs. Its manual gain control allows adjustment according to personal preferences and headphone/audio-system characteristics, making it suitable for a wide range of apps and devices. An MFB button is provided for pairing and music playback in Bluetooth mode. Volume buttons provide 60 levels of loudness.

The M18i supports seamless switching between Bluetooth and USB DAC modes. It features Qualcomm's latest Snapdragon Sound™ technology with Bluetooth 5.4, supporting AAC, SBC, aptX, aptX HD, aptX™ Adaptive, LE AUDIO, and 24bit/96kHz LDAC. Enjoy Bluetooth audio with all devices that support these codecs.

If the USB data and charging ports are both connected in PC mode, the M18i will draw power from the charging port. If a power adapter is connected to the USB charging port, the M18i will charge the battery regardless of the mode, and supports listening while charging.

The M18i ensures crystal-clear voice quality and call stability with Qualcomm's cVc Generation 8.0 call solution with ClearVoice Capture technology which suppresses environmental noise. The M18i also includes Infineon's flagship microphone, which can be used with wired headphones for voice calls. The microphone has a range of two meters.