From Ecoustics By W. Jennings
Dongle DACs became a hot commodity in 2021, but knowing which one makes sense for you and the headphones or powered loudspeakers that you own takes more than just a quick peek at the specifications.
Questyle’s M12 Dongle DAC which I reviewed recently was the luxury Chinese manufacturer’s first foray into the category and its performance made me realize that their long-term expertise in regard to high-end headphone amplifiers does matter.
Questyle doesn’t cut corners and the M12 proved to be much more capable than many of its rivals; the more expensive Questyle M15 isn’t a replacement and I was curious to see if the uptick in price placed it into the top tier in the category.
While the M12 is single ended with a 3.5mm jack, the Questyle M15 offers both single ended (via a 3.5mm port) and balanced (via a 4.4mm balanced port) sets of outputs.
The M15 is larger the the M12 but the weight difference is negligible and neither unit is difficult to travel with.
The M15 uses a metal shell on three sides and a glass face so technology nerds have something to look at. Unlike the M12 with its automatic gain switching, the M15 gives the user a manual switch on the side eliminating one of the complaints leveled against the M12.
The LED indicators of the M12 are retained with one on either side of the USB port. On the right hand side, we have a gain indicator with green for low and red for high; on the left hand side we have the data indicator with green for 44.1/48kHz PCM, red for high sample rate PCM (88kHz to 384kHz) and DSD64/256, and magenta for MQA files.
Much like its less expensive sibling, the heart of the M15 is the ESS9281AC SOC, and like its little brother — the M15 uses current mode amplification and bypasses the built-in amplifier in favor of a current mode amplifier designed by Questyle.
While most Dongle DAC manufacturers use the built-in amplifier for simplicity, the current mode amplifier Questyle designed has lower distortion and noise and offers greater bandwidth than similar voltage-mode amplifiers.
The M15 adds a Torex power management system to allow the M15 to deliver maximum output power without draining the phone’s battery excessively. I found that the M15 cost me roughly an hour of battery life on my Samsung S21 or iPhone 13 when listening at normal volume levels for a period of 4 hours.
The Questyle M15 is definitely not easy on your battery; it drains less than the Xduoo Link 2 Balanced Dongle DAC and is roughly equal with the Cayin RU6 which offers some of the best performance I’ve heard to date from anything in the category.
With two gain options, the M15 offers enough power to drive full sized headphones like the Meze Audio LIRIC and delivers enough finesse to handle sensitive IEMs using the low gain mode and single ended output.
Due to the use of the current mode amplifier, the measurements look a bit different than most; I still had no trouble driving the Beyerdynamic (600 ohms) headphones or Fostex T50RP with its low sensitivity.
The HEDD and HiFiMAN HE6 tax it heavily, but both can be used with the balanced output in a pinch although neither has a lot of extra headroom.
One quirk that must be highlighted is that a headphone or pair of earphones must be connected to the Questyle M15 before it is detected by the source device.
This design decision actually makes makes good sense since it can’t be used without a headphone connected and there is no point in draining power from the source unnecessarily. It is still not a feature you see very often and has led to comments online screaming about defective M12 and M15 models because end users don’t know about the feature.
Be sure you have a headphone or earphone connected to the M15 when plugging the USB cable into the source.
I had run into some driver issues with the M12 and wondered if they would rear their head as well with the two designs sharing the same SOC but thankfully found that whatever issue had plagued WASAPI in Foobar had been cured.
I had no issues with cutouts at all regardless of which device I attached the M15 to. Questyle lists the M15 as being compatible with Windows 10 but I suspect older versions of the OS might have some issues; it is something worth checking on the Questyle website.
What’s most striking about the Questyle M15 is the very linear and even performance across the entire frequency range; there are very few dips and I was quite taken with the levels of detail and texture.
Bass notes are delivered with excellent extension and impact and I noticed that unlike other Dongle DACs that have struggled with some full sized headphones in the low end, the M15 delivered a lot of energy, control, and speed.
The midrange is transparent, detailed, and rather crisp; vocals are not overly ripe making the M15 a good match for warmer sounding headphones or IEMs.
The treble is also clean, detailed, and not aggressive at all. It may not be the last word in treble airiness but it’s never etched or hard sounding with most recordings.
The soundstage with good headphones can be rather wide and deep and the M15 clearly bettered its less expensive sibling and others in that regard. Imaging is precise and I was quite surprised by how well it rivaled the Cayin RU6 in that regard.
The M15 isn’t soft or sweet and it is certainly not rolled off at either extreme; excellent recordings will benefit from its tonal balance and presentation.
The $249 Questyle M15 Dongle DAC certainly belongs in the premium class for a number of reasons; build quality, feature set, sound quality, and the ability to drive some rather difficult headphones.
With both single ended and balanced outputs, two gain levels, PCM, DSD, and MQA support, there is a lot to like about this product. Not everyone cares about MQA but those who use TIDAL will certainly want this feature.
Is it worth the uptick in price over the M12?
I would suggest that it rivals the Cayin RU6 and even some DAPs like the Hiby R6 and iBasso 220 which makes it a rather good bargain at the price.
Does it make sense to spend the additional funds on the Cayin RU6 or is the Questyle M15 now the model to beat in the category which also includes the AudioQuest DragonFly Cobalt and THX Onyx.
I would suggest trying it before you pay for anything else.