SIGMA Pro is Questyle's flagship portable DAC/amp, built on thier pursuit of audio perfection. It is a technological benchmark that proves performance and portability can coexist, delivering a truly portable "professional audio equipment" experience.

SIGMA Pro delivers desktop-class specs and sound quality. It houses four sets of Questyle-patented, fully discrete current-mode analog amplifier stages, a dual-mono ESS ES9069 DAC array, and an XMOS XU316 USB interface that supports master-grade PCM 768 kHz/DSD512 decoding and full MQA unfolding. 

Connectivity has been comprehensively upgraded, featuring multimachine recording monitoring, 3.5 mm single-ended, and 4.4 mm balanced analog inputs. The durable exterior is crafted from sandblasted aerospace aluminum and Kunlun glass. Independent dual USB-C ports support charging while listening, with an intelligent battery system ensuring stable, long-lasting power.

Built for professional, multi-scenario usage, the SIGMA Pro is about the same size as an iPhone 16 Pro Max (155.7 × 85 mm) yet weighs only 330.8 g, delivering desktop-grade performance in
a feather-light package.

The SIGMA Pro features a more powerful, fully discrete and balanced current mode amplifier. Delivering significantly increased output power and current, the SIGMA Pro effortlessly drives demanding high-impedance headphones for a full, dynamic sound, while also precisely controlling low-impedance IEMs for pure, detailed audio. The four sets of patented amplifiers elegantly resolve the conflict between size, power, and audio performance.

It also delivers a pure sound with loaded distortion so low it's almost imperceptible, and noise floor control that is astonishing, creating a "pure black background" for music, making you feel like you are in a recording studio.

To achieve decoding performance beyond customer expectations, the SIGMA Pro utilizes ESS's flagship stereo DAC chips, two ES9069 in a dual mono configuration, combined with the TTA three-level decoding architecture developed by Questyle engineers, delivering a performance fully on par with desktop devices.

Meticulously tuned by Questyle, the SIGMA Pro reveals delivers an uncolored, natural tone, revealing every detail as it was recorded.

The SIGMA Pro features 3.5mm, 4.4mm, and 6.35mm headphone output interfaces, combined with a manual gain adjustment function, allowing you to easily switch between work modes and personalized settings according to different headphones and listening scenarios without complicated operations, meeting diverse listening needs.

Whether it's optical/coaxial for lossless transmission, USB for convenient connection, or analog input/output for classic equipments, the SIGMA Pro, with its complete interface lineup, fully
covers different sources' connection needs. Whether building a desktop Hi-Fi system, connecting to professional work equipment, or matching home audio sets, it can accurately match different input sources and system configurations, realizing every listening idea and creating an unrestricted, diverse listening experience for the user.

The SIGMA Pro features 3.5mm (AUX IN) and 4.4mm (BAL IN) analog inputs, allowing it to connect to audio equipment like turntables and mixers. It can then convert the analog signal to a digital file for external storage, with synchronous monitoring during the process.

The Sigma Pro allows for up to 12 hours of battery life on a single charge.

It also supports dual USB-C ports, separating data transmission and charging. The audio USB-C port only transmits data, and the SIGMA Pro uses its own battery for power. Bluetooth mode only uses battery power, avoiding draining the phone's power.

The Power USB-C port is solely responsible for powering the SIGMA Pro system, allowing the user to charge the device during long-term use in fixed settings.