Questyle Audio Engineering unveils current-mode MEX dongle DAC in Tokyo

Questyle Audio Engineering showed off the MEX portable USB DAC and headphone amplifier at a Tokyo event on Nov. 7, 2026.

The MEX goes on general sale in Japan in December 2026 for ¥33,000, about $210 USD. Crowdfunding pre-orders on Mimigoto cost ¥26,400 and close on Nov. 29, 2026. Tech Times figures the pre-order at roughly $168 USD, whereas BigGo Finance puts it near $170 USD. Questyle has not announced an international release date or pricing outside Japan, though the company sells through standard retail channels in the United States, Europe and other markets.

Inside the MEX are two ESS ES9219Q digital-to-analog converter chips and four patented SiP current-mode amplifier modules. SiP, or system-in-package, bundles multiple functions into one module. The two chips handle conversion while the four modules provide amplification. Questyle says no other dongle DAC on the market uses current-mode amplification, making the design unusual.

In current-mode amplification, an input voltage becomes a proportional current, gets amplified in the current domain, and returns to voltage. The MEX supports native PCM playback up to 384 kHz / 32-bit and DSD256. It draws power from a connected USB port and has no internal battery.

At 300Ω, maximum output reaches 4V balanced and 2V single-ended. The impedance range runs from 8Ω to 600Ω, according to Questyle. Volume travels 64 discrete steps across High, Medium and Low gain levels. Outputs consist of a 4.4 mm balanced jack and a 3.5 mm single-ended jack that also carries microphone signals.

The MEX lacks Bluetooth or wireless and works as a wired dongle. A transparent skeleton rear panel reveals the PCB and four SiP module positions. Relative to the M15 predecessor, the MEX adds a companion app, dual-DAC topology and a PURE/TUNE switch.

Rivals at similar or lower prices include the Topping G5 portable amplifier, Shanling UA5 USB amplifier and iFi GO Blu Bluetooth DAC.

Questyle founder and CEO Wang Fengshuo spoke at the Tokyo event. Audio commentator Kenji Nomura said the MEX delivers effective noise reduction without a battery, and that PURE mode scores highly because of low distortion. Audio and DTM writer Ken Fujimoto recommended using the parametric EQ to fine-tune specific frequency bands rather than reshaping the sound dramatically. Voice actress and event MC Hibika Tamura said TUNE sounded crisper, while PURE sounded warmer and more cohesive overall.

A hardware PURE/TUNE slide switch bypasses the companion app when set to PURE mode, so listeners can use the hardware without installing the app. In TUNE mode, the companion app runs a 10-band parametric equalizer with five filter types. The app also adjusts Dynamic Range Extension, picks between two digital filters and sets left/right channel balance. The companion app works on iOS and Android and carries Apple MFi certification.

Wang Fengshuo said, “When you are confident in your engineering, there is no reason to hide it.” He also said, “Our stance is to show what’s inside for things we’re confident about.”

Questyle Audio Engineering is incorporated in Shenzhen, China, under the name Questyle Audio Engineering (深圳旷世之声文化科技有限公司). Under Article 7 of China’s National Intelligence Law, promulgated June 27, 2017, all organizations and citizens must support, assist and cooperate with national intelligence work. China’s Data Security Law, effective Sept. 1, 2021, requires organizations operating in China to cooperate with government requests for data access. Article 28 of China’s Cybersecurity Law, effective June 1, 2017, requires network operators to support and assist public security and national security organs.

These obligations apply to the app developer, though the hardware PURE mode allows use without the app. The hardware switch means buyers can skip the companion software entirely. There are no reported incidents of Questyle sharing user data with the PRC government.

The MEX appears on no US government ban list and is absent from the FCC’s Covered List. The app’s Apple App Store privacy label self-declares “No Data Collected,” though the claim is unaudited. No independent security audit of the Questyle app or MEX firmware has been publicly released.

Questyle filed current-mode amplification under PCT patent US 9,614,483 in 2004. Wang first showed current-mode amplification in the CMA800R in 2012. In 2022, a wave of customer service complaints about delayed orders and slow support responses documented concerns about Questyle’s operational scale. After launch, Questyle plans to add community preset-sharing.