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"Reviews

It’s been a while since I have been so thoroughly impressed with the performance of a portable source. The Questyle Sigma earns by unreserved recommendation and one of the highest ratings I have given to a portable source on this site. In terms of sheer sound quality, this will be endgame territory for many. Are there better sounding sources out there? Yes, but those cost significantly more and you may not even notice the changes with most IEMs."

"Questyle Sigma Review - Where Endgame Begins • Music For The Masses

The Questyle SIGMA demonstrates careful engineering aimed at delivering high‑resolution audio in a portable yet durable design. Its use of the AK4493 DAC and Current Mode Amplifier architecture provides desktop‑class decoding performance, while the transparent construction and retro‑inspired LED accents contribute to both aesthetics and functionality."

Questyle SIGMA Review » MOONSTAR Reviews

Questyle SIGMA – Portable DAC & Headphone Amplifier The name “SIGMA” derived from the 18th letter of the Greek alphabet, Σ, the mathematical symbol for summation. In this spirit, the portable SIGMA DAC/amp embodies the sum of all of Questyle’s audio innovations.

SIGMA was born from an uncompromising pursuit of excellence. It features an innovative TTA decoding architecture and supports decoding rates of up to PCM 768 kHz and DSD512 – performance otherwise achieved only by desktop devices. The patented CMA technology (Current Mode Amplifier) delivers professional performance in a compact format when combined with a fully discrete, fully balanced design.

Key features at a glance

• Outstanding audio performance: Equipped with the highly acclaimed AK4493 DAC chip from AKM and Questyle’s proprietary TTA architecture for desktop-class sound.

• Patented amplifier technology: Four sets of fully discrete, fully balanced CMA headphone amplifiers (Global PCT Patent No. US 9,614,483 B2).

• Apple MFi-certified: Official certification guarantees seamless compatibility and optimized power management with iPhones, iPads, and the entire Apple ecosystem.

• Premium Bluetooth (v5.4): Certified for Qualcomm Snapdragon Sound™ and Sony LDAC. Supports aptX Adaptive (lossless CD quality and high resolution up to 24-bit / 96 kHz).

• Special mode for in-ear monitors (IEMs): Dedicated IEM signal processing minimizes the signal path and provides ultra-fine 64-step volume control for a completely noise-free listening experience.

• No more battery worries: Built-in 4300 mAh lithium battery for up to 12 hours of playback. The dual USB-C system cleanly separates data transmission and charging.

Technical Specifications

Device Overview & Connections

Audio Outputs

• 3.5 mm Jack (Single-Ended): For standard headphones and IEMs.

• 4.4 mm Jack (Balanced): Fully balanced output for maximum dynamics.

• Note: The outputs can be switched from headphone operation to Line Out can be switched to connect the device to active studio monitors or Hi-Fi systems.

Intelligent Dual USB-C System

• USB DAC IN (Audio Port): Transmits audio data only. The device does not draw power from the smartphone, preserving the phone's battery.

• CHARGE IN (Power Port): Separate port exclusively for charging the internal battery (supports charging during use).

Controls & Switches

• Power Button: Press and hold for 2 seconds to turn on/off ; short press to display the battery level.

• Function Button: Short press to switch the input source ; press and hold to enter Bluetooth pairing mode.

• Volume Buttons (+ / -): Single click for 1 level ; press and hold for continuous adjustment.

• IEM/HP Switch: Switches between optimized IEM mode and standard headphone mode.

• Gain Switch & HOLD Switch: For adjusting the gain and locking the buttons.

LED Status Indicators

• Audio Source: Separate LEDs for Bluetooth, USB, gain level, data stream, and active IEM mode.

• Battery & Volume Indicator: LED matrix for battery levels (25%, 50%, 75%, 100%).

Package Contents & Accessories

• Questyle SIGMA Portable DAC/Amp Unit

• USB-C to USB-C Cable (12 cm)

• USB-C to USB-C Cable (120 cm)

• USB-A to USB-C Adapter

• Warranty Card & User Manual