QUESTYLE M15 Review: A Very Capable Dongle (the king?)

THE PLUS:
-Clear and neutral sound with lively dynamic
-Excellent Pace, rythm and timing (PRaT) performance
-Great imaging with open spatiality
-realist timbre with good transparency
-weighty dynamic
-clean linear current amping
-gain switch
-more powerfull than the specs suggest (75mw@32ohm)
-doesn’t get hot or drown battery too fast
-best ES9281C DAC implementation i heard
-great balance between technical and musical audio decoding
-versatile pairing with high sensitivity and high impedance IEM
-unique geeky design for circuit board lover

THE MINUS:
-while powerfull, it will struggle to drive very low sensitivity IEM or Headphones
-micro-definition isn’t the cleanest nor the sharpest
-bass and treble seem just slightly tamed
-glass cover can be scratched and is worrysome for durability
-protective case make it hard to use gain switch

TONALITY: 8.8/10
TECHNICALITY: 8.8/10
CONSTRUCTION: 8.2/10
AMPING POWER FOR THE SIZE: 8/10
SOUND VALUE: 8.5/10

QUESTYLE is a chinese high end audio company specialize in amplifier, DAP and DAC-AMP. They have been around since 2015 and are known for their high end DAP like the well receive QP1R and QP2R, as well as for their deskop amplifier and lately for their portable DAC-AMP (dongle).

Another thing that Questyle is know for, it’s their patented Current mode amplification technology, which permit to achieve class A amplification quality in a more compact factor. All their products use this type of amping circuitry which is acclaim by audiophiles.

Today, I will review their latest portable DAC-AMP release, the M15. Priced 250$, this mid-tier dongle use a sabre ES9281AC DAC with four CMA (current mode amplificator), which promise highly dynamic sound rendering as well as top of the line audio performance.
Let see in this review if the price is right for such a small DAC-AMP.

CONSTRUCTION

Unique you say?

The M15 have a very original design that is sure to catch the eye and even make you suddenly curious about audio circuitry. Its made of metal body with the top all made of glass that permit to see the whole circuit board, including dac and amps chips.

This design is wise too, since it have 2 light indicator on the board, one for data transmission and other for gain selection. Data indicator light color will change depending of codec rate, green for anything under 48khz, red for anything hi res between PCM 88.2kHz~384 kHz, or DSD64~DSD256 and magenta for MQA streaming. Gain light color will be green for low gain and red for high gain. This is very practical yet subtle in it’s presentation.

Rest of body is made of metal with a black mate finish. Front of the device have one 3.5mm SE jack and a 4.4mm gold plated balanced jack. The back have a USB-C connector. Left side of the body have a metal gain switch. Everything feel well crafted.

You can buy a leather protective case for 25$. In all honnesty, at 250$, i would have expect it to be include in accessories, which include 1 basic USB-C, one USB-C cable and one USB-C to USB cable and a USB-C to lightning cable . It doesn’t include USB-C to lightning cable, another potential extra cost for Iphone user.

Packaging is minimal, nothing really to write about and as noted, inclusion of a protective case would have been very welcome.

Lastly, about this protective case, i’m not sure of it’s exact purpose apart adding a classy touch to the M15, since the glass isn’t protected and will still be prompt to scratch or perhaps breaking if drop on the hard floor.

AMPLIFICATION

High gain 4.4mm: 72.72mW@32ohm – 1.525Vrms- THD+N=0.00139% Impedance= 1.22ohm

High gain 3.5mm: 42.25mW@32ohm -1.163Vrms- THD+N=0.00084% Impedance=0.96ohm
(thanks to Questyle for sharing me this precise info)

Compared to several portable dongles delivering 4vrms in balanced mode, the M15 may seem very limited with its 1.525Vrms in high gain balanced mode, fortunately this does not translate into impressions of loss of volume or dynamics because even the Sennheiser HD820 can sound full, open and loud with their 300ohm.

So, with my tests, I would conclude that this type of power limitation will be more problematic for earphones or headphones with low sensitivity than low or high impedance with normal or high sensitivity. For example, the Final E5000 have an impedance of only 14ohm but a very low sensitivity of 93ohm, which seems to conflict with the type of amplification of the M15 by not allowing the transducer to act correctly, which creates invasive distortion and compressed sound. This case of the E5000s is an exception and no other IEM or headphones have suffered this tragic fate.
Despite an output impedance that may seem high for very sensitive or low impedance IEMs, the rendering of M15 remains clean, balanced and without distortion for sensitive IEM, as the Audiosense T800 (9ohm) and Dunu DK2001 (110db-32ohm) proved it.
So my advice here would be to avoid earphones or headphones with very low sensitivity and maybe opt for an impedance of 16ohm and above to be safe. The M15 will have no difficulty correctly driving 99% of theIEM, earbuds and headphones on the market, with a power well felt in its dynamics and without distortion or invasive hiss.

The current mode amping technology used by Questyle is nothing like voltage amplifier using OPamp for extra gain.

”Current Mode Amplification features the use of transistors to amplify and a fully discrete structure, to wit: voltage input and output, while the core amplification takes place in the current domain operating in a pure Class A state. It is completely different from the traditional voltage mode amplifier in the structure of the amplification circuit. Current-mode audio amplifiers affect the speed and bandwidth of the transistor-level capacitance between the low impedance nodes, not only completely eliminates the transient intermodulation distortion (TIMD), but can easily attain ultra-high bandwidth (full power bandwidth of 500kHz ) and ultra-low distortion (lower than 0.0002% THD+N, challenging the physical limits of audio testing). The Current Mode Amplification technology can be used for amplifiers of any power level (10mW-2000W) and of any size (thousands of square centimeters for some professorial amplifiers).”

But how does it translate in sound perception? Well, imagine a THX AAA amplifier, like SMSL SH9, but with greater dynamic impact and denser more natural timbre, and your not far from M15 amping experience. Current drive seem to deliver power in a different way too, resulting in louder sound than it’s 75mw suggest. I’m not sure to know how to explain this, but the fact it was able to drive correctly and without distortion or compression in dynamic the Sennheiser HD820 is sure impressive. 

SOUND IMPRESSIONS

TONALITY

A neutral rendering but not flat in dynamics which it approaches more the W shape with an injection of weight and density in the low, medium and high. Everything in timbral and tonal balance is natural and cohesive. It’s not colored while being not clinical or cold in the rendering too, it borders on the analytical without having any spike or imbalance in the rendering of the frequencies which would harm the cohesion of the whole. It’s crisp yet well rounded balance.
Still, the widest frequency band is the highs and the M15 keeps this in focus, preserving its fullness of rendering and cleanliness of presence. In my opinion, here we are in the best of worlds where romantic musicality and a high degree of technical performance meet and embrace each other in complete naturalness.

RESOLUTION & PRECISION

With the M15, we are not in warm or dark territory, nor in artificial amplification of clarity, certainly the resolution is very high and will make you discover new details in the music you listen to, but without pushing them forward with aggressiveness or too much amplification of the texture to make their presence stand out.

Here, Questyle has drawn the full potential of its saber ES9281 DAC thanks to a clean, linear and varied amplification in its dynamics. Macro-resolution is favored here, it’s vast and detailed, transparent and revealing. The sound layers cut across spatiality while keeping intact the well-defined presence of static elements. The definition of micro details is between analytical and softened neutrality, which somewhat polishes the sibilance of aggressive IEMs like the Final A8000s, and also densifies the timbre a bit. I wouldn’t say that the noise floor is 100% black, because the silence between instruments is a little vibrant, but it’s not far from it, especially when using IEMs and headsets not intensely sensitive to output impedance.

The precision is very high with the M15, even in fast and complex passages the rendering is very articulate and defined in the separation of its attack. But the M15 has a slightly rounded sound at each end, so the sub-bass will be a little more difficult to pin down or feel, and the very high frequencies will not be perfectly sculpted.
Being familiar with this ES9281 DAC, I can confirm that the M15 pushes its technical performance to its peak, including its level of resolution, transparency and definition of these micro-details.

DYNAMIC

One of the most difficult aspects to describe is the dynamic rendering of an audio source, which is often more dependent on its type of amplification than on the decoder itself. Here, I feared that the M15 rendering would be too flat and linear, similar to a THX amp, and thank God, this is not the case at all! We are in the best of worlds with the M15, which balances between attack speed and resolving capacity with a desire for musicality well felt in the heaviness of impact and the reliefs of diversified attack amplitudes. The impact of the notes has weight, the piano does not sound flat. The mid-bass hits hard, with a nicely sculpted roundness. The high frequencies are incisive in the attack and restore as much in their body and harmonic presence. This dynamic doesn’t create much resonance after impact, which is good for bass impact and also midrange control, but a bit less for more airiness and echoing super high-frequency brilliance. .

OTHER TECHNICALITIES

The spatial presentation is well balanced between width and depth of scene, and also very realistic. It doesn’t sound closed, it’s circular and full, with no presence hole. It’s wide and reasonably deep but won’t enlarge your headphones’ stage unduly. What matters here is that it doesn’t compress the rendering or affect its accuracy, which is fully the case with the M15. The sound imagery is really impressive, without artifice we have a natural separation of the moving sound layers and enough well-defined space between the static instruments. It’s not analytical but naturally revealing, even I would say that the entire sound spectrum is treated in the same way, so no micro high details better separated than the rest accentuating an impression of air and space. As for PRaT (Pace, rhythm and timing), it’s excellent here and proof that we have a mid-range DAC-AMP of high quality and fidelity. The M15 will never muffle or distort excited passages of speedy busy music and deliver sharp timing into full articulation regardless of the attack speed.
The density of timbre is amplified by the longer sustain of the notes than their impact resonance time, so no, the micro separation of each note playing at crazy speeds will not be magnified or shadowed by a mixture of impact resonances.
Attack sustain-release is central to precision, accuracy and attack speed definition. Here, the M15 is not 100% perfect and my SMSL SU-9+SH9 stack is cleaner and more precise in sustaining and detonating sounds. Still, the M15 is superior to all my other DAC-AMPs at this level, including the Tri TK2 and Xduoo Link2 Bal, which have more harmonic distortion and impasto when I play the frenzied jazz rock album ”Dodovoodoo” by Elephant9.

COMPARISONS

VS XDUOO Link2 Bal (dual cs43131+independent Opamp-270mw@32ohmbal-160$)

There are two big acoustic differences that strike the informed listener when comparing these two excellent DAC-AMPs, these are the wider stage width and height of the Xduoo as well as its warmer resolution and less clear and precise than the M15. Immediately, the technical performances of the M15 seem higher, both in the control, the synchronicity, the speed and precision of the counterpoints of the attacks and the cleanliness of resolution in the macro and microscopic sense. The M15 is more neutral, less colored by warmer, looser and boosted bass. This may make its dynamics seem weaker and limited in amplitude power, but this is not the case if we compare the treble rendering which is more pushed and extended, delivering and extracting micro details with greater ease, this which is evident in fast and complex passages of music, where the Xduoo will show some limitation in terms of saturation and distortion, both higher than the M15. Xduoo has a warmer, analogous and fleshy tonality, with thicker and opaque sound layers, it favors relief more than the texture of the timbre and its transparency than the M15. Its highs shimmer less and get lost more in its fluffy sonic ensemble. M15, without being cold or clinical, delivers less soft and rounder basses in their impact, and a more precise, articulated instrumental separation without adding color. The Xduoo remains a superior DAC-AMP in terms of construction and tactility, having a volume control, a gain switch and even UAC 1.0 and 2.0 selection switch, but above all a chassis that seems extremely durable compared to the pretty body of the M15 which has a glass certainly interesting for the eyes but worrying for the durability. In the end, the M15 offers a more neutral and detailed tone with superior technical performance and slightly less powerfull amplification to the Xduoo Link2 Bal.

VS TRI TK2 (dual ES9038q2m+A\B amp-1250mw@32ohm-280$)

What strikes the listener in the first place is how the spatiality is wider, grand and open as well as the dynamics more corpulent and heavy in impact. The general resolution is more subdued and not as clean with the TK2, without being dark, only less precise and cut in its separation and less clear in the definition of each instrument. The M15 is more neutral and analytical, with a thinner and more textured timbre, better transparency but a more closed and condensed scene. The bass is more colorful with the TK2, warmer and boosted with a less defined but more resonant hit, which tends to make the transition with the mids more veiled and organic. Here, the M15 does not force the bass overflow into the mids and keeps the separation clear while delivering a more energy-focused and resonantly controlled strike. The mids seem a bit flatter and set back with the M15, but more centered and less diffuse in their separation. High frequencies are drier, clearer and more textured with the M15, delivering more energetic and fully rendered percussion. The TK2 is about 5 times bigger and heavier than the M15, it is not really portable and its gain is triggered when you pass a certain volume level, I would have preferred a switch like the M15. Technically speaking, I would conclude that the M15 is superior due to a darker noise floor, higher resolution, more precise instrument separation as well as a more controlled and less diffuse attack, however I tend to prefer the warmer, natural and open tone of the TK2 because the instruments have more body and a wider and creamier projection, but my conclusion in terms of musicality might be different with less aggressive IEMs than the A8000.

VS Xduoo Poke II (dual CS43198 dac-700mw-390$)

Another excellent DAC-AMP using current amplification, but this time with an ES9281C saber DAC. Also, without battery and with supposedly lower amplification force although more energetic in its dynamics. Here, the M15 delivers meatier, vibrant and warm bass with more pronounced impact heaviness. The resolution is almost identical, although less finicky in the micro-definition, favoring a roundness of tone denser than the Poke II. In terms of precision and separation, the Poke is an iota superior because it is clearer and cleaner with a more restrained attack in its echo. The M15 has a spatial rendering that has more relief and sculpture of presence, giving a more holographic and open effect in height and width. The spatiality of the Poke is deeper with more static instrumental positioning, more defined and focused in the high frequencies. The flatter, more clinical rendering of the Poke tends to be less immersive and encompassing for the listener than the M15, which despite a technical performance of high resolution and a bit lower micro-details, delivers a more natural, physical and tonally accurate musicality.

PAIRING

With the FINAL A8000

These exceptional intras are my reference no1 because the presence of all the frequencies is fleshy, dynamic, clear and precise, nothing is behind and despite a few points in the bass, midrange and high, the balance is intended to be energetically neutral. . With an overly aggressive DAC-AMP, the A8000s can scream a bit and the M15 doesn’t cause this while preserving their high resolution and dynamic energy. The first thing I notice is that the basses are more textured and transparent, preserving their heaviness of impact without boosting their resonance. The sub-bass is not pushed back or attenuated and vibrates naturally without taking over the mids with a surplus of presence. The mids are less prone to sibilance than with a FIIO KA3, but don’t gain much body, it remains fairly centered with high clarity and good separation. It’s not compressed but not very open either. The highs gain in fullness of timbre but not in brilliance or resonance In terms of spatiality, it gains in depth while maintaining an average width and height. The instrumental separation is not negatively impacted but does not gain space. Let’s say that the A8000s remain faithful to their deep nature with the M15, without added color, their tone or timbre is not boosted any further, and their technical performance is accentuated in controlling their extremely fast attack. Still, I would have preferred a little more addition in terms of dynamics and also the presence of bass.

With UM Mext

These two seem to be made to go together, the presentation here is so beautifully balanced, corpulent in dynamics and highly resolute. MEXT basses gain in roundness, texture and immediacy of impact. The mids are superbly resolved, clear, transparent without grain but nuanced in texture, here it’s open and frontal, it seems that the bone conduction driver appreciates the amplification while running, it’s clean, wide of stage and natural , truly breathtaking. And what about the highs, again a similar treatment, but less thin and shiny than with some other dongles like the Tempotec E44. The amount of sound information is infinite but transmitted delicately, and once again, the completely black background accentuates the cleanliness of the space, improving the resolving complexity and instrumental separation as well as the depth of the scene. Truly, if you’ve owned MEXTs and are looking for the perfect dongle to do them justice, the Questyle M15 is its soul mate.

With MOONDROP ARIA

I would have thought that this pairing would be perfect, but it’s not exactly that…here we have clearer and more aggressive Arias, with more emphasis on texture and dry tone. The bass, which was already lacking a bit of well-felt punch, does not gain any advantage, although the kick drum has more texture and a gripping presence, and it seems that the sub-bass extends and vibrates less too. The mids are less organic, leaner and drier, with a flatter presence and less open projection. The highs gain in texture and grip, suddenly the electric guitar sounds surprisingly good, with a rich and transparent distortion, more bite in the attack, something that was often missing with other dongles such as Tri TK2, Xduoo Link2 Bal, but what is strange is that the body remains thin, so the guitar lines do not have this heaviness and immediacy of presence.

With the FINAL E5000

Here we have IEMs known to be difficult to drive correctly and I will be short because indeed the E5000 creates a disaster with the M15. I was expecting a little compressed sound but here it’s distortion problems with the bass that ruin the listening. But not only. The transducer really doesn’t seem to like the current type of amplification and I don’t know how to explain this. The entire dynamic becomes distorted at the slightest increase in diversified amplitude mixing different frequency spectra. At low volumes, this won’t be as problematic, but the E5000s will sound flat in dynamics, compressed in image and too emphatic in the highs. If you plan to use M15 for the Final E5000, I strongly advise against it.

With the Audiosense T800

Let’s start by saying that the T800s are sensitive to the amplification impedance and the M15 is not the lowest on this side (more or less 1ohm). Fortunately, this does not result in extreme distortion, although sometimes present at high volume, especially with high gain. At low gain, the rendering is tonally linear and dynamically energetic. The bass is more textured and less boomy and resonant, which accentuates the clarity of the T800s and makes them more balanced neutral because the highs are not amplified. The vocals are less prompt to sibilance and a little less open in width. I would say that the T800 loses cleanliness and analytical clarity in more complex passages, which does not happen with a lower impedance source like the Xduoo X20 or Ibasso DX90 (0.1ohm).

CONCLUSION

In the last years, i’ve been spoil with alot of great sounding dongles, ranging from 20$ to 500$. Lot of them were redundant too and not that much of a big sound upgrade in the 20 or more I try or own. So, I learn exceptional sounding DAC-AMP are rare when it come to plain sound quality.

Here, with the M15 we are in mid-costy territory, so my expectation were very high. To conclude that it offer high sound value mean it’s able to compete with pricier DAP or DAC-AMP in sound quality, and thanks to the magic of current mode amplification as well as good DAC implementation of Questyle, this DAC-AMP deliver a sound quality that fit or even surpass it’s price tag. It’s literally end game dongle for everything but perhaps end game amping power.

The M15 might be the only ”reference” ultra portable DAC-AMP out there, in the sens that it deliver an high fidelity neutral sound with heavy dynamic heft and natural yet crisp resolution. This high end dongle know how to sign and dance, it have enough power output for majority of IEM and Headphones while not being hungry for your phone battery life, and hey, it show you it’s geeky soul under the glass of it’s body too!

Highly recommended!

———

PS: I want to thanks Questyle for sending me this review unit and answering all my questions too. It was a very pleasant communication, very generous, transparent and informative. I’m not affiliated to this nice company and share my 100% independant honnest audio impressions as always.

You can buy the Questyle M15 for 250$ from this official seller:https://www.linsoul.com/products/questyle-m15?variant=42702297497817

For more info about Questyle and their products, check their official site here:
https://www.questyle.com/language/en/cmafifteen/