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 from 44.1 to 768kHz—the M12’s specifications say 384kHz—and with DSD data from DSD64 to DSD256. The data status LED illuminates green for PCM data, red for DSD data. The M12 can also work as an MQA renderer, performing the final unfold of MQA data when fed from an MQA-compatible source that performs the first unfold. The status LED glows magenta with MQA data.
The M12 can be used with computers, of course; no special driver is required with MacOS and Windows 10 v.18.3 and above. It also works with tablets and smartphones and is compatible with iOS and Android 5.1 and above. Included in the box are two adapter cables: one USB-C–USB-A cable to use with computers, and one USB-C–USB-C cable for use with devices running Android. Those who wish to use the Questyle with an iOS device will need to purchase a USB-C–Lightning adapter cable with an OTG (“On the Go”) interface. According to Questyle, the M12’s Torex DC/DC converter combines high efficiency with low power consumption to maximize smartphone battery life.
Listening
I had been impressed by the sound quality on offer from Questyle’s QP1R hi-rez portable player, which I reviewed in December 2015, so I looked forward to what I was going to hear from the M12. Using the USB-C–USB-A cable, I plugged the M12 into one of the USB ports on my late 2014 Mac mini and plugged in a pair of AudioQuest NightHawk headphones. The Questyle’s Gain LED glowed green—as expected, since the NightHawks have an impedance of 23 ohms. The Roon app didn’t recognize the M12 but did identify it as an ALSA device. I selected the M12 as a playback zone and set it to receive DSD data over PCM (DoP), to render MQA files, and to allow its volume to be adjusted with Roon. Then I started playing music.
The first piece I played was Antony Michaelson’s 2003 performance of the Mozart Clarinet Concerto (16/44.1 ALAC file, Musical Fidelity Recordings), recorded by Tony Faulkner in London’s Henry Wood Hall, which I produced. The image of the clarinet was clean and clear, with the orchestra unambiguously presented to the sides and behind. The low strings in the orchestra were warm sounding, perhaps a bit too much so. I played Pat Martino’s Live at Yoshi’s (16/44.1 FLAC, Blue Note/Tidal). This was a recommendation from Sasha Matson when we were discussing guitarist Martino’s passing last November. Martino is joined on this album by Billy Hart on drums and Joey DeFrancesco on Hammond B3 organ, and the bass lines, played by DeFrancesco on the organ pedals, were somewhat loose-sounding.
I replaced the AudioQuests with Sennheiser HD 650s, which have an impedance that varies between 300 ohms and 500 ohms. The Gain LED glowed red, and as I started playing Live at Yoshi’s the instruments were confined to the center of my head—mono! The Sennheiser cable was terminated with a ¼” plug, and I was using a generic ¼”–3.5mm adapter cable. I fiddled with the 3.5mm plug in the M12’s jack, and mono turned to stereo. The Hammond organ’s bass pedals now had a better balance between low-frequency weight and control than they had with the NightHawks.
I replaced the Sennheisers with the Audeze LCD-Xes that I had purchased after my review in March 2014. The Audezes have an impedance of 22 ohms. The M12’s Gain LED turned from red to green, and I had no connection problems with the 3.5mm plug on the Nordost Heimdall cable that I was using with these headphones. The M12 did a good job controlling both the Hammond’s bass pedals with these ‘phones and the orchestra’s low strings in my Mozart recording.
Streaming the Martino album reminded me that Billy Hart had played drums on the first multitrack digital recording I had made: pianist Marc Copland’s quartet with guitarist John Abercrombie and bassist Peter Herbert, and Hart, at a private concert for the Santa Fe Chamber Music Festival in 1997. The late Wes Phillips, who had been at the concert, described Hart as about the quietest drummer he’d ever heard. Hart “uses silence in large blocks,” he once wrote, explaining that Hart’s playing featured a very wide dynamic range. I didn’t use any compression in mixing this recording, so it was a good test of the M12’s ability to preserve low-level detail while at the same time handling the high-level peaks.
Hart starts Copland’s “Billy’s Bounce” (16/44.1 ALAC file, unreleased) with a quiet dotted pattern on snare and hi-hat but gradually increases the complexity of the accompaniment, exploring the different textures of his ride and crash cymbals as first Abercrombie then Copland take solos. When Hart takes his own solo, the sounds of the toms, snare drum, and kickdrum were well-differentiated. The final rimshots on the snare almost took my head off when, seduced by the clarity, I set the M12’s volume to “100”!
The M12 handled DSD data with aplomb. An album I have mentioned several times in my reviews is violinist Christian Tetzlaff and pianist Lars Vogt’s superbly idiomatic performances of the Brahms Violin Sonatas (DSD128 files, Ondine ODE1284-2D/HDtracks), especially the first sonata. Pressing “Play” in Roon turned the data status LED red, and the violin sounded appropriately delicate and the piano suitably majestic when required, both instruments suspended in a subtle ambient halo.
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COMPANY INFO
Questyle Audio Technology Co., Ltd.
US distributor: Bluebird Music Ltd.
1100 Military Rd.
Kenmore, NY 14217
(416) 638-8207
bluebirdmusic.com
ARTICLE CONTENTS
Page 1
Page 2
Specifications
Associated Equipment
Measurements
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