Questyle M15 · Mobile Lossless Headphone Amp with DAC

You get what you pay for; not with the Questyle M15, you get much more! If you don’t want to read further, let me make it short, you get top class desktop grade audio performance in DAC that fits on the palm of your hand.


The M15 uses Questyle’s patented current amplification technology featuring Class AB amplification. I am not going to pretend to understand all the intricacies of current amplification technology, but I can say that what Questyle did, it works and it works damn good! There is only one thing about the M15 that I don’t like and I am going to get it out of the way in the beginning, that is the absence of volume control buttons or knobs in the unit.




Physical Attributes & what's in the box:


The M15 looks unique with a glass front letting you see the circuitry inside it. This might be for everyone but I quite like it. I was a bit apprehensive at first about the glass built, but that feeling didn’t last long after using the unit for a while. It does not feel flimsy in any way and I can’t imagine it breaking unless something heavy falls on it. The glass is covered by a thin film of plastic to protect it against scratches. The rest of the body is made of machined aluminum, nothing special there. It has a small switch in its size allowing you to change the gain between high and low. On its front is a USB C port and on the back is a 3.5mm and a 4.4mm port allowing both single ended and balanced connection. The packaging is fairly modest, it just includes a type C to type C and a type C to type A cable.


Specifications:


Output Power： 3.5mm:RL=300Ω,Po=11.97mW

Vout(Max)=1.895Vrms,THD+N=0.00045% 4.4mm:RL=300Ω,Po=22.60mW, Vout(Max)=2.624Vrms,THD+N=0.00057%


Questyle just mentions the power output at 300Ω, so I was a bit confused at first about what to expect but in handled everything that I threw at it with flying colors.They used a ES9271AC DAC capable of handling PCM：PCM: 32kHz – 384kHz (16/24/32Bit) DSD： DSD64(1Bit 2.8MHz) , DSD128(1Bit 5.6MHz), DSD256(1Bit 11.2MHz). The background noise is less than -125dB and I could not hear any noise during my listening. It also acts as a MQA decoder (for those who care).




Pairings:


I tried the M15 with almost everything I had in my arsenal curious to see how it handled each of them:

1. Dunu Zen Pro
2. Sennheiser HD6XX
3. Audeze LCD-X
4. Hifiman Arya V3
5. Koss Porta Pro

The M15 did not fall short with any of them.


Sound Impressions:


Power:The M15 delivered power to all my headphones and earphones leaving nothing to be desired more from such a portable device. I used the M15 with my google Pixel 6, Shanling M7 DAP and also from my PC. With the portable devices, in high gain, I did not have to increase the volume more than 50% to drive the HD6XX, Arya and LCD-X pretty loudly. The Porta Pro and Zen Pro all played fine at low gain. But when I connected the M15 to my PC, it became a different monster. At 30% volume, it was driving the Arya at ear splitting levels. I had to adjust the volume carefully to find a comfortable listening level. I haven’t seen a lot of entry level desktop amps output this amount of power. That being said, the M15 did pick up some noise when connected to the USB port of my computer, but I guess that is to be expected because we know how noisy those ports can be.


It drove all 3 of my headphones with authority which matched the level of my Burson Audio Soloist 3X. While the Soloist 3X is way more powerful, I really don’t need that amount of power for any of my cans. I haven’t found any dongle yet, bar the M15 which can properly drive the HD6XX.




Tonality:M15’s tonality is neutral but not cold, I enjoyed all of the aforementioned pairings a lot. What surprised me most is that I liked the pairing of the HD6XX of the M15 more than the pairing with the Burson Soloist 3X. The Soloist 3X is a class A amplifier, but compared to the M15, the Soloist and HD6XX pairing is a bit too warm for my taste. It muddies the sound of the 6XX a bit. It’s a well known fact that the Sennheiser HD6 series prefers a warmer source, but not to my ears. The 6XX sounded more organic and natural to me with the M15, spewing out details that I have seen from $500 upward amps. Listening to Jeff Buckley’s “Mojo Pin”, “Last Goodbye” and “Lover, You Should’ve Come Over”.the vocals were full bodied and lush, solidifying the 6XX’s strong suites.Questyle showed with this dongle that the complaints we used to hear about ESS’s “digital sound” is just not true anymore, far from it. It sounds as analog as analog can get.




Technical Performance:The technical performance comes very close to the Soloist 3X paired with the Topping D90SE DAC, which totals at $2000 retail. The M15 is a detail monster with a very natural presentation. The D90SE using the top of the line ESS 9038 Pro DAC provides ample details needless to say. But the way M15 does it is more natural and does not seem “in your face”. It drove the LCD-X and the Arya with speed and prowess that I did not feel the need to resort back to my desktop amp. The attack and decay of both the planars were blazing fast. I used the track “Festival in Bagdad - The Sea - The ship Goes to Pieces on a Rock” by Chicago Symphony Orchestra and Fritz Reiner to test the speed, separation and how it handles complex passages, also “Pace” by Nubya Garcia. The separation between the notes were excellent and distinguishable. The dynamics and resolution it provides is excellent, more understandable with well recorded tracks from any genre. I was able to hear the faintest sound of brush drumsticks on the far right in a track, the brush dragged along the drum. While I found the imaging to be fine, my only gripe is that the soundstage could be a bit wider, but I am really nitpicking here. I am comparing the soundstage with the other attributes of the dongle.


Bass:The bass response from the M15 is clean, precise, fast and powerful. With the LCD-X and the Arya they slam hard. Listening to the “Burning down the house” by Talking Heads, the bass was textured and layered. I used “Angel” by Massive Attack to test the sub-bass. It reached pretty low and with prowess. With the Zen Pro too, the bass is rumbling.


Mids:The mids is one of the strongest traits of the M15. Both male and female vocals sounded full and lush. It wasn’t pushed forward in any way, neither was it recessed. It was textured, nuanced and I got the feeling that I was listening to the vocals just as the mixing and mastering engineers intended. The mids are almost … addictive.


Treble:To test the treble, I played “Batonga” by Santana. If a headphone is sibilant, I can usually tell from the female vocals of this track. None of my headphones sounded sibilant in any way, it was airy and natural and energetic. Treble lovers like myself will quite enjoy the M15. This is unlike how a lot of Chinese manufacturers reproduce the treble from their dongles.


All throughout the frequency range, the music flows like water. No frequency is over accentuated, none is recessed.




Conclusion:


Who is this dongle for and who should buy it? This dongle is for anyone who prefers a clean, neutral and engaging sound. It's for anyone who does critical listening without losing the enjoyment factor. It is for headphone users like me who prefer headphones over earphones, it can most probably replace your desktop setup and you will be happy that it did. It can mop with probably any dongle that’s out there and a lot of desktop DAC AMPs. The M15 might be the only source that you might need for a very long time.

Introduction to the Questyle M15 review​

Questyle is a Chinese company that has been on the market for quite some time now. Unlike their other counterparts at the time, they always aimed at the premium market. Quality and performance, over low prices. One of the first purely Chinese companies that actually threw a challenge in the face of more established companies on the market. That is something to admire, as it was in complete opposition to what their competition was doing. There also is a more personal story that I have with Questyle.
I can remember the company appearing on the Polish market as I was learning the ropes of audio reviewing. I even listened to the CMA600i, I believe, but left the website before I got it in for a review. Guess, who later did that review. The one and only, Paweł from Ear-Fidelity. What makes it even funnier is that we actually didn’t know each other yet. He was my replacement when I left. Who’s that guy, with that ridiculous hairstyle? Somebody mentioned he looks like a pineapple. It lives rent-free in my head now.
Well, now we are good friends and today he’ll be at my 30th b-day party. Maybe I’ll buy him a pina colada… Small world, huh? It’s worth noting that the review was very favorable, and he even said it was one of the best devices available at the time. I’m not translating that directly from Polish, so let’s say you trust me on this one.
Questyle saw the rise of portable audio and the need for the best possible sound quality outside the home. That inspired them to create the subject of this review. The M15 is a portable Hi-Res DAC/AMP, a so-called dongle. It connects to your phone via a USB type C cable and allows you to utilize your IEMs and headphones on the go. Its goal is to combine Hi-Res audio, capable amplification, and premium build quality. Did they succeed? This review of Questyle M15 will tell you everything.

Packaging​

I’m fresh after doing the Andromeda Emerald Sea video (check it out on YouTube!), with its absolutely crazy packaging. Well, here we have the absolute opposite.
We only get the most basic box, holding essentials. In the box you’ll find: the dongle and the USB type C pigtail cable. Done. Whoa, reviewing the Questyle M15 is so easy.
The leather case is available separately for $25 in a couple of colors: black, red, ivory, green, brown and grey. I got the black one because it was the only one that I could grab locally, but bet your ass, that Ivory would look absolutely stunning.

Design and Build Quality​

I have to say, that the reviewed M15 lives up to the “Questyle hype” from my memories. Seems that the company hasn’t strayed from those “ancient” times. The body is made out of milled aluminium and the top is made out of either acrylic or glass. It’s like a back window in a Lamborghini. It’s not for you to safely park backwards. It’s so you can see the engine! In this case, the electronics are on the display. Why can’t girls get me that aroused? Laser-engraved markings and text cover the whole device. You can see that it is not a cheap toy. Fitting is impeccable.
The user experience was really good, especially after I bought the leather case, and stopped worrying about scratching it so much. Still managed to get a tiny scratch on the glass, curious if you can spot it in the pictures.
The dongle has one neat function: when nothing is connected to the output, it turns off to conserve energy. My main issue with the reviewed Questyle M15 is the fact that it doesn’t have integrated volume control. You control the volume from your source. My Samsung S21 FE 5G has a ridiculously large step (something around 10%) which can’t be changed in the settings. I had to find a program called Sound Assistant that allowed me to change that and reduce the volume control steps. Besides that, using the Questyle M15 is great.

Tech inside the reviewed Questyle M15​

The Questyle M15 features a couple of interesting solutions, which I’m more than happy to nerd out about.
Let’s start with the star of the show, the ESS Sabre ES9281AC codec. It’s an impressive IC, integrating a USB Audio interface, very good DAC, ADC, and some other features like output jack detection. How they managed to fit all that in such a small package is beyond me. It supports PCM 32bit/384kHz and DSD256.
On top of that, Questyle’s engineers implemented their flagship technology, the CMA (Current Mode Amplification) SiP headphone amplifiers. Four of them to be exact. Current mode amplification is not as popular as voltage mode amplification, but some manufacturers swear by it, including Accuphase. Current mode amplifiers are the most known for their speed, they can handle some very high-frequency signals.
The SiP has a bandwidth of 1 MHz with only 0,0003% distortion. Those are some nice numbers. What about the power? You won’t catch the reviewed Questyle M15 slacking. The official data shows 22,6mW @ 300 Ohm with no rating for the 32 Ohm load. Output voltages are rated at 3,5mm: 1,9V and 4,4mm: 2,6V. I know it’s hard to compare those numbers with other dongles. In my experience, the reviewed Questyle M15 is more powerful than I would ever need it to be, driving Meze 99 Classic and low-sensitivity IEMs with ease.
For our convenience, we can select gain, either low or high. I would prefer the low gain to be actually lower than it is. I still don’t have as much volume control over the Andromeda ES as I would like to. Also, the high gain is very high and even the headphones I tried didn’t need that much. The power supply used is named Torex and is focused on keeping the efficiency as high as possible.
I have to admit, that while on low gain the reviewed Questyle M15 uses minuscule amounts of energy. My phone is very happy about that. Not having to load your phone after a ride across the city is a nice feature. One last thing. The M15 has a rare tendency to pick up some interference while not playing. Like once a day. This doesn’t happen at all when listening to music, but c’mon Questyle.

Sound​

Most of my testing was based on Campfire Audio Andromeda Emerald Sea and Unique Melody MEST. I have used Time Stream cable for the Andromeda and Erua Audio Tawa for the MEST. I tested driving capability on Meze 99 Classic (no issues) and HiFiMan Sundara Classic (didn’t work that well). Other IEMs used in testing: Letshuoer EJ07M, Craft Ears Aurum. Dongles used for comparison are listed later on. As usual, I’m using 4,4mm connections wherever possible.
Well to start off, no surprises here really. First of all, the sound quality is really high. Questyle is one of the brands I would consider a safe choice quality-wise. Secondly, it sounds like it has a Sabre chip. Incredible dynamics, powerful bass, good sound staging, clear-cut sound, and black, velvety background. It sounds like some of my other reviews, but it’s not my fault that ESS Sabre dominates the market. I’m aware of that, but not much I could do about it.
Okay, I have something new for you! The newest generation of Sabre DACs is not as fatiguing to me as the previous ones and that applies to the one used in the reviewed Questyle M15. They had to change something in the design. The tonal balance of the M15 is a bit boosted in the top and bottom ends. It builds extra excitement and increases the foot-tapping factor, but it may not be the best thing for studio usage. Let’s dive into more details.

Bass
The first thing I have noticed with the Andromeda is how well the Questyle M15 drives them. Zero noise, maximum dynamics. I was dumbfounded at what bass the ES started producing. Big, bold, with the punch of a martial artist. It is more snappy like a lightweight MMA, than a heavyweight boxer, but still.
Listen to Kanye West’s Black Skinhead, this song really benefits from the reviewed Questyle M15’s sound character. In the beginning, you get a heavy drum bass with some quick jumps left and right on the soundstage. Controlled aggression, lightning-fast transitions, and complete silence in between the sounds really took me off guard. It’s absolutely amazing how the Andromeda ES transformed under the M15’s iron grip. On the other hand, a bass line from Starlight, by Muse has incredible complexity to it.
It goes throughout the song, and you can try it as a reference for textures. It’s a big sound with lots of detail with drums on top of it all. It’s a great test for equipment and you can see how much control the Questyle M15 has when drums come in after the intro and the bass line doesn’t lose anything. I’m thoroughly impressed by the performance of the Questyle’s dongle.



Midrange
The midrange is slightly recessed in comparison to other ranges, but it doesn’t lose its qualities. Great things are expected from dongles at this price point. Reviewed Questyle M15 delivers. One of my favorite pop artists Dua Lipa has this incredible show at Tiny Desk. Tiny Desk is an acoustic, live music show on YouTube. You can find big names mixed with a lot of indie artists from different genres. Dua Lipa might have one of the best ones.
Her sexy, pleasant voice is supported by a choir, a guitar, and a bass guitar. Add some simple samples and you’ll be blown away. My favorite song from the show is Pretty Please. Just layers of voices, after around 40 seconds the choir starts to take a greater part and with the mix of Andromeda ES and Questyle M15, you can listen to each voice individually. It made me happy to be able to enjoy one of my favorite shows to this degree. Are you craving something more fancy? How about an indie artist named Kevin Morby? On his album Sundowner, you can find this song called Brother, Sister.
Wait till the first chorus, where he uses vocalization followed by an acoustic guitar. The amount of insight into the sound that you are getting is really good. It is crazy how such a simple composition can speak to your emotions. Courtesy of the Questyle M15.

Treble
When it comes to treble, the M15 pushes them a bit harder, which is compensated by the Andromeda ES softness at the top. For this part, I relied more on the UM MEST. The treble of the Questyle M15 is big, and controlled.
The intro to the Sanitarium by Metallica features guitars supported by cymbals. Especially the first one sounds with a suitable impact. Emphasis on treble helps here to add extra energy and freshness to a pretty complex composition by one of my favorite bands. I do feel like the treble on the reviewed Questyle M15 tends to be a bit metallic, even when it comes to sounds that shouldn’t sound like that. Clandestina (Cocaine remix) by Filv, Edmofo, and Emma Peters is the song you know, but couldn’t remember what it’s called.
No thanks are necessary. Here the M15 presented a controlled and clear-cut sound, that sometimes felt a bit too hard. It is still a really good performance, but later on, you’ll learn about competition that does it better.

Soundstage
One of the biggest tests for sound staging was Dua Lipa’s show at Tiny Desk. I’m surprised by how well are those shows recorded. Reviewed Questyle M15 allowed me to easily place all of the musicians and singers in front of me.
Each of them was a separate sound source with no mixing between them. They were very close to me, as both Questyle M15 and Andromeda ES tend to have a closed-in presentation. For sound staging reasons I preferred the MEST with its tendency to explode the sound and push sources away from the listener.
The Questyle M15 does a good job at soundstage width and depth, but the competition is one step ahead. Really good performance on the part of M15.

Comparisons​

Cayin RU6, NOS – $249

The RU6 by Cayin is one of the first dongles (if not the first one) to feature an R2R DAC. It promises and delivers a completely different sound signature than Delta Sigma DACs. It pushes the midrange into the first line. The treble and bass are pushed to the side a fair bit. The soundstage is much more open than on the Questyle M15. Refer to the Dua Lipa Pretty Please as a reference track. Pretty please.
Same thing on Clandestina (Cocaine remix), everything is much more open with more air between the instruments. In terms of bass, it is the weakest in the amount and the quality. Whether it’s Kanye West Black skinhead’s intro that lacks the bang, or Muse’s Starlight, with its famous bassline lacking the detail. It’s the bottom of the comparison here. Midrange, on the other hand, takes the cake, and with the Andromeda ES… It’s a crazy experience. I could have RU6 only to listen to the midrange. Kevin Morby’s Brother, Sister is magical. Natural, bold, thrilling voice and guitar. Absolutely top-tier performance. Neither M15 nor W4 have anything to say here.
With Dua Lipa’s show? Don’t even ask. I’m in love with her, just didn’t inform her yet. Please, call me. Pretty please? The treble on the RU6 is not as pronounced as in other dongles but is very light, sweet, and open. Less aggressive in Sanitarium by Metallica, either in the beginning or close to the end, it holds its own and compensates the amount with quality. Oh btw, don’t use UM MEST with the RU6. It doesn’t sound good. Anti synergy, just like me and pineapple pizza.

L&P W4, TUNE 1, Filter SLOW – $450

The W4 is still pretty fresh, as it had a premiere this year. The top dog from Luxury & Precision uses the LP5108, which is a combo of two DACs from Cirrus with some power regulators in a single module. I think they might oversold it a bit, as people feel deceived by the nature of the module. Still, there are some merits to doing that, namely great power delivery and decoupling.
You might have noticed the price tag. Yes, it’s not a typo. It is crazy expensive for a dongle (besides the ridiculous Gold Bar from iFi Audio). Yet still I can’t deny, that the W4 seems to be the best dongle on the market. In the top 3, no doubt. It takes the pros from both the M15 and RU6 but leaves out the cons. Pretty balanced character (with a small bump in bass), lots of power, and a great sound. It’s gonna be hard to return it to the owner. Thank you Grzesiu for lending it to me. Sound staging of the W4 is precise as with the M15, yet open and spacious as with the RU6. Take Dua Lipa’s Tiny Desk concert and it will be a top-tier performance.
The bass is not as powerful and dynamic as with the M15, but it still is excellent. Power, control, and detail. Doesn’t break a sweat with Kanye, and neither does fine detail with Muse. The midrange is not as good as with the W4, but it is pretty close. Detail, natural timbre, and smoothness can be heard throughout the whole Brother, Sister by Kevin Morby. Treble is another win, being the best out of all tested devices.
Open, airy, and sweet, but with enough authority to balance other ranges. The W4 played well with both the Andromeda ES and the MEST. It is a complete package, but it costs basically the same as the other two dongles combined. So, you know…

Pairing​

I will compare the pairing with the help of Tom Cruise and his two best roles.

Andromeda Emerald Sea



Andromeda ES with the Questyle M15 is like Tom Cruise in Collateral. Vincent was precise and calculated, yet charming and incredibly dangerous. The darker tuning of the Andromeda means you might want to use the silicone tips to get a more balanced response. The amount of precision this combo gives is incredible. As mentioned in our Andromeda ES review on YouTube, the Questyle M15 became my daily driver.
The bass from this combo will break your stereotypes about BA IEMs. It’s crazy good. The dryer midrange of the ESS Sabre family is greatly supplemented by the IEM’s richness in this regard. It still has plenty of charm. The top end gets dominated by Andromeda ES’ roll-off, so as mentioned before, you either deal with it or use silicone tips. I can live with that, as it is still a very respectable performance. All in all, incredible combo, and I can see myself using it for a long, long time.

UM MEST



The MEST with the M15 is like the best role of Tom Cruise. As a wise man named Les Grossman from the movie Tropic Thunder once said:
Now I want you to take a step back… AND LITERALLY *** YOUR OWN FACE!
You can’t censor me, it’s a movie quote. This combo is just an obnoxious level of fun. It’s like the titular character, completely over the top. They will take you on a ride with a bass bigger than his bald spot. It will make you break some dance moves like Ludacris’ You don’t know me like that is in the air. But, on a more serious note. It’s a great combo.
The set with Andro is for enjoying music. This one is for enjoying yourself. Huge soundstage, with sound sources all around you, like assistants circling around Les. The Bass is something the MEST is known for with its bone conduction driver and the Questyle M15 takes full advantage of that. Just an ungodly rumble. The SiP amplifier is a very capable one. The midrange is on the back foot here as both devices don’t make it a priority. It’s still solid for the price, but let’s be honest.
You don’t buy the MEST for midrange, don’t you? The treble does an amazing job of countering the bass and making sure it doesn’t steal the show. Bright, bold, open and smug. Cuts through the low-frequency fatness like a pickle cuts the fatness of a pork belly on a sandwich. So to summarize it all, it’s an illegal amount of fun. If you like to always have fun, when listening to music, it might be a combo for you.

Questyle M15 Review – Summary​

Good to see, that Questyle didn’t lose its direction over the years. Their focus is to make high-quality audio equipment and this review confirms that in my eyes. I have no doubt, that Questyle M15 is one of the best dongles on the market. Premium build quality and a fantastic sound are a testimony of that. While not as feature-packed as its competition, it steals the show with detailed, v-shaped explosive sound and great drive capabilities.
If you like the stereotypical sound of ESS Sabre DACs, you’ll be in heaven. Or maybe you are interested in a stupidly good-sounding dongle, that won’t drain your battery in 3 hours?

It’s not flawless though. The RF interference it can pick up when music is not playing is something that should be addressed. It happens very rarely, but still: shouldn’t. The other feature I dislike is the lack of integrated volume control. I would prefer not to use my smartphone for that since it was a challenge to figure out how to adjust the volume control step.
All in all, M15 still deserves a recommendation. I’m happy to use it as my daily driver, as it replaced my iFi Audio GO Bar. If you are on the lookout for a dongle that will drive anything while sounding mighty, you need to try the Questyle M15.


Highly Recommended.

Big thanks to Questyle for providing the M15 for this review. I wasn’t paid or asked to say anything good or bad about this product, all of the above is just my personal, unbiased opinion.

Had I been a YouTube reviewer, I would have littered a ton of “fire” emojis across this review title. The thumbnail would allude to something akin to “shut-up and buy it”, while a somewhat disturbing image of my agape face would round-up the level of bewilderment and bemusement that the M15 has evoked.

Sadly, in the written form, I am but slave to the words.

Questyle M15 is the flagship dongle in the brand’s lineup, and overall, perhaps the best dongle one can buy. Sadly, such sweeping generalizations do not favor anyone, and everything is reliant upon context.

So, this review is to contextualize the reasons why the Questyle M15 might be the best dongle ever, or why it may not be the right dongle for certain use-cases. Read on.

Note: the ratings given will be subjective to the price tier. Thanks to Questyle for sending the M15 for evaluation.
This review originally appeared on Audioreviews.
Price, while reviewed: $250. Can be bought from Questyle’s Official Website.

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PACKAGING AND ACCESSORIES​

The packaging is minimal, while the accessories are basic. You get a type-C to type-C cable by default. For Apple users, the lightning cable is sold as a separate bundle for USD$20 premium. There is also a nice leather case that you can purchase separately.

BUILD QUALITY​

Questyle opts for a CNC-milled aluminum chassis with a see-through acrylic window for the M15’s design. It’s a simple yet effective design decision to go for a see-through top, as it makes the M15 stand out without going overboard. Questyle is not new to this, as many of its desktop products offer an acrylic top for those so inclined.



In terms of inputs and outputs, things are decidedly simple. The type-C port allows USB connection while the 3.5mm and 4.4mm jacks offer unbalanced and balanced connections respectively. The balanced output sounds markedly better as an aside, but that is the case for nearly every dongle that offers a balanced output.



There is a button on the side for gain control, and that’s about it. No volume or playback buttons are there which might be an issue for some. There are two LEDs on the PCB that shines through the acrylic, one for gain level and another is the file type indicator.



Overall, a very simple yet elegant design that panders to my inner-geek thanks to that PCB that’s been laid bare.

HANDLING​

At 61.8mm X 27.2mm X 12mm dimensions, the M15 is not the most innocuous of dongles in terms of size. However, I find it to be fairly practical on the desk and the low 25g of weight makes carrying it around easy enough. Even after prolonged usage, the M15 does not get hot which is another plus.

QUESTYLE M15 INTERNALS​

Questyle has a knack for making pretty PCBs. Even the desktop DAC or amps have exceptionally clean PCB layout, and the M15 is no exception. Thanks to the acrylic window, all of it is in plain view. Apart from the ES9281AC DAC chip and the aforementioned status LEDs, you can also see the two SIP (system-in-package) current mode amp modules. Each module handles one channel.



There is also a TOREX power management unit that keeps the M15 inactive when no music is playing. In terms of specs, you get a really respectable 0.0003% THD and <-130dB SNR. Then you notice the output power specs and things just do not add up. A measly 22mW into 300ohms? Surely that cannot be right?

In terms of the actual “sound pressure” produced, that indeed seems to be misleading. The M15 can drive most dynamic driver headphones and nearly every single IEMs out there. Only issue is that for best performance, you need to use a laptop as the source. The higher current from the USB ports enable greater dynamic swings.

Speaking of dynamic swings, the SE out can have almost 2Vrms voltage swing from the single-ended out, and about 3.8Vrms from the balanced out. You can connect the M15 to a pair of powered monitors in a pinch and use it as a DAC/pre-amp combo. Just make sure to put the volume at max on the DAC side.

All in all, respectable measured performance, except for the amp specifications which do not really add up to real world experience.

TONALITY AND TECHNICALITIES​

As always, it’s difficult to simply talk about the “tonality” of a source gear rather than specific pairing notes. That being said, the M15 has certain “characteristics” that shine through no matter which IEMs or headphones you connect on the other end.

The first thing you notice is the resolution, and how easily the M15 delineates between instruments. Rest assured, the amount of perceived details on the M15 eclipses any other dongle under USD$300. Minute details are pushed to the forefront, making it easier to analyze and dissect tracks. If it’s resolution and precision you want, M15 is practically peerless.

Such hyper-realistic rendition comes at the cost of two things: spatial qualities, and a tendency to be ruthless with poorly mastered tracks or bright/shouty gear. The M15 is unforgiving, though the lack of “etchiness” in the treble and upper-mids make it a potent option for borderline bright IEMs and headphones. The staging won’t be engulfing or stretched outwards, like it can be on some of M15’s peers.

Dynamics are good in terms of macrodynamic punch, though microdynamics are not as evident as they are on certain desktop sources (or even Questyle’s higher-tier DAPs).

Finally, the power output is ample for practically any IEMs out there. When connected to a laptop or desktop, the M15 is too powerful for most IEMs, in fact. I routinely found myself lowering the gain and/or lowering the volume on the desktop side. This is still not enough for power hungry monsters like Hifiman’s HE-6, for example, so for the pesky planars, you still need a more substantial setup.

PAIRING NOTES​

I’ll try to keep this section short and sweet.

IEMs that paired well with the M15: most of them, but highlights include Sennheiser IE 900/200/300, SoftEars Turii, Final E3000/A5000/E4000, JVC FW1800/FW10000/FDX1, Campfire Holocene/Andromeda 2020/Solaris.

Headphones that paired well with the M15: not the absurdly power hungry planars, including the likes of HE-6 (and Susvara, by extension, though I fail to understand why anyone would try to run Susvaras off of a dongle), Sennheiser HD800S (too bright), and Beyers (same issues as the Senns). The HD650 had a good pairing though it lacked the liquid smoothness you get off of tubes or high output impedance sources.

Hifiman HE-400i and Arya sounded exceptional through the M15, and if you own the Arya Stealth (or even the newer Arya Organic), the M15 will be more than enough to do justice to their resolving prowess.

SELECT COMPARISONS​

I have pitted the Questyle M15 against every single “hyped” or well-regarded dongle that has been released so far. None of them are as resolving, period.



Quloos MC01 gets close at the cost of sounding edgy in the treble and artificial throughout. Apogee Groove has better rendition (and sense) of space, but it sounds a bit veiled in the bass and treble comparatively. The Cayin RU6 are too smoothed out, while the Cayin RU7 opt for a more relaxed, engulfing, and timbrally-accurate presentation than going after raw details.



Lastly, the L&P dongles (W2 and W4) do better in terms of microdynamics but fall flat in every other aspect. The output power is lacking compared to the M15, and once again – not as resolving.

CONCLUDING REMARKS​

I received the Questyle M15 back in November, 2022. At the time of writing this review (end of July, 2023) the M15 managed to ward off every single competition by the wayside.

It’s a remarkable achievement in the age of rapid-fire chi-fi releases, where even the parent brand makes its 6 months old “flagship” redundant by releasing something new and “improved”. The M15 is here to stay, and shall remain one of the best, if not the best DAC-Amp dongles out there for the foreseeable future.

The only caveat is the nature of the sound itself – it may become “information overload” for those accustomed to relaxed and laid-back tuning. With certain IEMs, the treble region can sound exaggerated and become bothersome in the long run.

These caveats apply to most, if not all products though, and the M15 achieves the one thing it set out to accomplish: the crown for the most “effortlessly resolving” DAC-Amp dongle out there. Questyle captured lightning in a bottle with the M15, and I hope the spark does not go out anytime soon.