Questyle Audio M12

There are words that, for reasons I can’t fathom, I cannot stand. One such is “dongle.” So when Bluebird Music’s PR rep emailed me to ask if I would be interested in reviewing a new dongle from Chinese company Questyle Audio, I shuddered. But I must admit that “dongle” rolls off the tongue a lot more readily than “portable USB D/A headphone amplifier.” I put aside my grammatical quibble and agreed to a review.

The M12

Priced at $139.99, the tiny, 2"-long M12 Mobile Hi-Fi Headphone Amplifier with DAC features a case machined from aluminum. On one end is a USB-C port. On the other is a 3.5mm stereo headphone jack. On top are two multicolor LEDs, one to indicate the gain setting, the other the incoming data status. On the bottom are logos for MQA, ESS, and “Current Mode Amplification.” That’s all there is to see.

The M12’s complexity lies inside. “Current Mode Amplification” refers to a “patented SiP amplifier module” that Questyle says provides “high” current output, “vanishingly low” distortion, and “astonishing noise levels of–130dB.” The “Smart Impedance Detection” feature refers to the M12’s ability to detect the impedance of headphones when they’re plugged in and automatically set the gain to the appropriate value. With low-impedance headphones, the M12 switches to low gain, and the Gain LED glows green. With high-impedance headphones, like my Sennheiser HD 650, the M12 switches to high gain and the LED glows red.

D/A conversion is performed with an ESS ES9281AC DAC chip. According to the chip’s datasheet, it works with 16-, 24-, and 32-bit PCM data sampled at all rates