Questyle M15i — Mobile Headphone Amp & DAC

Overview
Preface
I purchased my M15i with my own money from Amazon, all thoughts and opinions are my own.
The M15i was put on my radar because I was in the market for a nice DAC/AMP for my IEMs and headphones and I had been using Questyle’s cheaper M12i for a while. I kept them in mind for a while before eventually pulling the trigger.

Initial thoughts
I will break everything down later on.
Very easy to use, just plug it in and start playing music right off it. The 2 red LED lights turn right on indicating that it is on and working, and the gain switch causes no pops or breaks in sound when flipped while audio is playing. The audio has a natural, uncompressed quality that sounds great, with no artifacts or noticeable issues. The part I like a lot about its sound is the treble, on a lot of IEMs it seems to add nice detail to the upper treble.

Design
I absolutely love Questyle's designs. The clean sleek matte black metal body with clean text and a small tactile switch for gain modes, and the best part, the front window. The black chip, copper 4.4 plug, and red LEDs just look beautiful, I always appreciate when companies make clear tech show the beautiful inside and Questyle did it very well with no wires or eyesores inside.


Unboxing

• Questyle M15i
• USB-C to USB-C cable
• USB-C female to USB-A male adaptor
• User manual
• Specs sheet

The no-nonsense package includes everything you need to use it happily and does not need any aftermarket accessories. Everything is well-built, and the packaging has a very good design and typography for those who appreciate marketing design. No complaints whatsoever.

Sound
Overview
As I mentioned before, the sound is very clean and just very good. The bass stays tight and clear without bloating, getting too soft, or becoming smoothed over, the mids just sound right, and the treble is affected in a very pleasing way. The upper treble region gets a little extra spice and detail but doesn't become any brighter or harsh, sometimes it even helps smooth peaky treble.
One downside is sometimes I’ll hear a digital buzzing like once every one or two hours, messing with cable connections fixes it usually, also usually happens a bit after plugging in an IEM. Not a deal breaker for me but definitely something to keep in mind.

Headphone and IEM pairings

Nightjar Singularity
This is the IEM that benefits the most from the M15i. The Singularity can sometimes be perceived as slightly dark or veiled in the treble region, which sometimes is an issue when I want more detail out of my music. The M15i kind of opens up the treble and adds the detail I miss, it also seems to add a bit more texture to the treble, plucks on guitars, and breaths in voices become a bit more tactile and alive.
The Singularity is an IEM that is very well known for its top-tier bass performance which can be very much affected by the source it is being run off of. On my other main source which I use on the go, the FiiO BTR17, while good, it is a bit lacking when compared to the M15i. The bass still slams and rumbles on the BTR17 but when I switch from one to the other after using one for a while, I can really feel the difference in the bass, on the M15i, it just feels more controlled, while on the BTR17, it can sound a little soft and smooth. The same goes for my Schiit Magni Unity.

7th Acoustics Supernova
The Supernova tends to be quite easy to drive and make sound good, but it becomes a little tricky with sources when it comes to the bass. I generally don’t believe in “BA bass” but the Supernova’s bass is done by dual BA drivers and on a lower-quality source, that fact becomes more apparent. On the M15i, the Supernova’s bass is very tight and punchy, on my BTR17, the bass is also good but it lacks a little bit of impact that the M15i has.
The Supernova is also a brighter IEM with amazingly smooth treble but can get harsh on sources that might affect the treble, the M15i doesn’t give it the upper treble zing that I get on the Singularity and still keeps it very smooth.

Symphonium Crimson
The Crimsons showed me the biggest example of smoothing harsh treble, when I had the Crimsons on hand, I needed EQ to bear the upper treble on them but when I used them on the M15i instead of the BTR17, the treble seemed a bit smoother and more bearable without EQ

Sennheiser X Drop HD6XX
I am generally more used to IEMs and hearing sound differences on them so I don’t hear many major effects the M15i has on the 6XX. The main thing to appreciate about the M15i with the 6XX is that it can easily power them to well above comfortable listening levels. Before getting my M15i, the best source for the 6XX was my Schiit Magni Unity, but when it comes to sound, the M15i edges out the Magni. The 6XX seems to come a bit more alive and sounds a tad less sterile next to the Magni.

Introduction

The Questyle M15 is often cited as one of the leading USB DAC/amp dongles available. I owned it myself for some time and was overall very impressed with the performance. With the M15I, Questyle have improved on the foundations of the M15 by adding Apple compatibility and tweaking the performance.



I will the specs and techs linked here for those interested, but the salient details are that the M15I is employing a current output mode amplification, which is novel. In addition, the M15I uses an ESS ES9281AC chip, which, while not top of the line, is still very capable. 4.4mm and 3.5mm headphone jacks are provided for, with the balanced output providing more output.

Build and Design

The M15I is a handsome unit. It feels great in the hand, with a premium quality to the build and materials. The body has a glass case revealing the inner workings of the unit, not least the Japanese made Pentaconn 4.4mm socket which is always preferable to any generic alternative. Although sturdy, a leather case is available which adds protection without increasing bulk.



Interestingly, the M15I like the M15 does not have a hardware volume control. Volume is controlled by software alone, and the only switches on the unit are for gain. Some may find this off-putting, but in practice I found that the absence of a volume control on the unit seems to generate a much blacker and cleaner presentation. In practice, controlling the volume with an app such as UAPP or Hiby’s music app works perfectly and I would not be perturbed by the absence of a hardware control; if anything, it’s a benefit.

Sound Impressions

The overall sound impression of the M15I is dynamic, fairly linear but with a slightly v-shaped tilt. Bass – especially sub-bass – has a slight tilt, which provides an energetic and quite muscular delivery. The mids are textured, but perfectly linear while the top end is airy but not strident. This is a “musical” presentation without being overly lush or warm. In general, I think listeners will likely find it engaging and quite atmospheric while also avoiding fatigue. With respect to technical aspects, the M15I delivers quite comfortably on all fronts. Imaging and layering are quite defined, with an impressive sense of precision for a dongle.



The other point concerns dynamics. For a dongle, the presentation is remarkably authoritative with respects to dynamics. On Sennheiser’s HD800s, you get an impactful and surprisingly weighty presentation, which is no small thing for a dongle to achieve. There’s a lot to be said for the use of current mode amplification here. If you’re judging the M15I on stats alone, you’re missing out on what the current output amplification is capable of. To put this in context, using Roon as the software volume, I need only go to 20 out of 100 steps for the HD800s to shine – not only for them to have volume, but for them to perform exceptionally well. For other dynamic headphones such as Sennheiser’s newly released HD620s, the results are impressive; with the M15I rendering the HD620s a lively yet well balanced headphone.



Comparisons

The only dongles I have to compare are Lotoo S2 and Ibasso’s DC-Elite.

Vs. Lotoo S2: S2 is warmer, more restrained, and less engaging. Its strengths are a clean background and the benefits of the LCD display. Overall, however, it is less dynamic and less engaging than the M15I. Some people may find Lotoo’s more relaxed tuning more appealing, but in a direct comparison, the M15I operates on a higher tier technically.

Vs. DC-Elite. While the M15I is an impressive dongle, the DC-Elite outperforms it on all levels. It is much wider sounding, with sharper resolution, punchier dynamics, and a presentation that basically transcends the dongle format. Thar said, the M15I offers fantastic value for money and is highly competitive in its price range.



Conclusion

With the M15I, Questyle have improved on already outstanding dongle by rendering it even more capable and refined. As a go to dongle for everyday use, I can highly recommend it.

Review Of The Questyle M15i​

Introduction​

This is my second time reviewing a Questyle product. Questyle is a Chinese firm that specializes in electro-acoustic equipment, particularly DACs and amplifiers. Recently, they have entered the IEM industry as well. I first learned about this firm when I heard about one of their Dongle Dacs, the M15, which I personally purchased and enjoyed since there was no other Dongle Dac that could exceed it at the time. They just announced another lineup that includes the CMA18P, M12i, and M15i, of which I recently reviewed the CMA18P but was hoping to get my hands on the other two as well. Fortunately, I was able to obtain the M15i; however, before proceeding, I'd like to clarify a few points.

Disclaimer​

*Since this unit tour was organised by the kind people at Questyle, I am grateful to them. And as I've said in all of my evaluations, the same is true for this one: all of the concepts I've expressed below are entirely my own, original ideas that haven't been influenced by anyone else. If interested, go to this link.
*I am not associated with the connection, and I receive no financial assistance from anyone.
*For the remainder of the review, I will refer to this device as “M15i”
*Finally, I will only evaluate the M15i based on its performance, even though I will explain how it feels and seems physically and aesthetically.

Specification​

The M15i's high-end ES9281AC DAC chipset supports native DSD256, 32-bit/768kHz PCM, and two separate SiP CMA amplifier modules. While the majority of the functions remain the same as the predecessor, one significant distinction is that the M15i employs TOREX precise power management technology. The M15i is a more user-friendly device that accepts Type-C and Lightning data transfers, as well as 3.5mm single-ended and 4.4mm balanced connectors. The device has a gain control on the side and a type-c connector on top. Four LEDs behind the glass display the gain level and send data. The M15i includes a Type-C to C OTG cable and a Type-C to USB-A converter. Regarding technical aspects, the data in the table is listed below for your convenience and comprehension.

Design And Aesthetics​

In terms of design and aesthetics, I believe it is identical to its predecessor, with the same frame, body, and dimensions. The body is composed of CNC anodized black aluminium alloy, and its dimensions are approximately 61.9mm X 27.9mm X 12mm. As previously said, there is a glass layer above the chipboard, which is within the aluminium block; while I am sceptical of the durability, having owned M15 before, I can tell that it is not a concern. Aside from the glass, the build seems solid, and from the looks of it, I still think it's quite useful and compact for what it can do.

Usage ​

With my usage, I found it to be as pleasant as previously; the cable itself seems stable, and the use with my smartphone is quite pocketable. The nicest aspect is that I can also use it with my iPhone using a lightning OTG cable. The M15i has a bigger body than the DEW4X, DAWN Pro, and Allegro, but its form factor makes it more comfortable and secure than any other dongle I've tested. Regardless of my personal preference, the dongle is larger than the ones I described.

Sound Impressions ​

IEMs​

Thieaudio Prestige LTD

Prestige LTD is the very reason I am now able to find the truth in my musical dreams; I have never heard another IEM that ploughs your ears with faith in each note, no matter how those notes should sound and nurtures your senses with dynamics and presentation as if I were hearing reality. Previously, I owned the Monarch MKII, which established what one would expect, but once the prestige's magic began to flourish, I knew I could explore so much more with it, especially when it came to the air and presence of each nuance the notes were able to grasp over and tingled my senses. To summarise the prestige's response sounds as if the Monarch MKII were given steroids and enhanced the upper frequencies in all directions with better authoritative flow in the lower response. The response is neutral with sub-bass boost, similar to the Monarch MKII, with the exception that the notes are airier and more revealing than any other IEM before this era. However, the thinner notes and excessive clarity provide obnoxious features that expose bad mixing and recordings, which were highly obvious when heard on my V6 but smoothed out on my WM1A, indicating source dependence.



When I listened to this coupling, the response seemed nicely spread out and forward in the mid-range, particularly the vocals. The presentation sounded less expansive, but the note expression was more textured and detailed, with a bright contrast that allowed for a far more resolved response, resulting in a more analytical approach to the mix. Whether I'm listening to Kool-Aid by Bring Me The Horizon or Miliyah's Kono Yumega Samerumade, there's a lot going on that sounds really revealing and vivid without being confusing or overlapping. Surprisingly, the entire presentation sounds entertaining and intriguing.

FlipEars Aurora

Aurora establishes itself in this market as one of the greatest musical and warm-sounding IEMs, providing a detailed but calming response that even my Prestige LTD cannot match. To be more specific, the Aurora has a warm-neutral sounding response that enables for a cohesive and effortless sound regardless of the music I choose. When it comes to the Prestige LTD, I believe the clarity, realism, and tonal correctness are the greatest. Aurora bends that will and produce a profound sense of natural sound that sounds precise and clear enough to provide harmony into the mix, which is better done on these IEMs. Because of the way the treble is adjusted, the response does not lean clinical or sterile in the upper harmonics. The midrange produces a spacious sound, and one will fall in love with the note’s depth, weight, and precision. The bass's impact hits you so hard that it leaves you in wonder due to its rapid striking and natural decay of the notes, which is backed by two subwoofers, resulting in a highly robust production of bass heaviness and presence without sacrificing clarity across the spectrum.

When I listened to this pairing, I saw that the response, which was energetic, thrilling, and engaging, enhanced in terms of what Aurora does well. Satellite by Valentino Khan is a great example of this, with its shimmering treble, revealing mid-range, and firing subwoofers packed with strong and impactful thumps and punches all sounding more textured and detailed, with better control over attack and decay of the notes allowing more details to conspire and more room for them to sound full and rich. However, in tracks such as Kohana Lam's A Few Sentimental, the vocals are unexpectedly sweet and tranquil, with a more upfront approach that provides a deeper and richer experience.

Thor Mjolnir MKII

Mjolnir is a very bassy set that has a lot of sub-bass emphasis. The treble and upper mid-range are also very forward in the mix. The upper treble has great extension as well. The bass is very punchy and boomy while acting fast. Mjolnir is a great V-shape-sounding IEM with a different approach to explosive bass that has better technicalities, especially in this price range. The stage is great with a nice surrounding stage and depth where the separation of each element sounds distant enough to procure space to breathe and distinguish themselves. The attack and decay of the driver capability are really quick and perform great. The vocals may feel lean and sparkly, but the warmth or the fuller experience is something that these lack. The bass response does vary from source to source whether I listen to a warm source or a neutral one, the bass becomes either overwhelming authoritative or both.



While listening to this pairing, the response sounds more transparent with better control over the revealing aspect of the treble region and upper mid-range. Usually, when I listen to clear and neutral sounding sources, the energy in the upper frequencies spikes a lot, causing me to respond to sound fatiguing and very intimate sounding, like for example Anytime and Anywhere by Millet had vocals forward and present in a very revealing manner which was very well balanced. With M15i, the response sounds well-resolved and expansive, while the note exposure improves, making the sound more mature and detailed. However, the bass seems as dominant as before, with improved control and punch in the low end, particularly while listening to Erotica by JAWNS, when the bass left deep and impacting with a powerful presence.

7Hz Aurora

Trust me when I say that Aurora is a literal detail monster, as every aspect of the presentation oozes out details and clarity with a versatile tuning that allows the intricacies and nuances to shower over the mix, bringing excellent clarity and transparency to the presentation. Though I notice that the existence of such notes results in sharp characteristics, I have never experienced a metallic nature. The crispness and air in the treble area, as well as the lively tone of the midrange, combined with a large stage that allows notes to breathe and sound full, result in remarkable detail retrieval. The nicest thing of the entire response is that the definition and tonal balance are nicely established, resulting in a lean yet coherent-sounding presentation. If I look at the graph, it appears frightening with peaks and dips over the treble area, however, such a presentation produces a vibrant and enticing response that isn't overly bright while also including crisp and sparkling aspect of the notes. On the other side, the midrange sounds broader and clearer without adding hotness or peakiness to the mix, while the bass may become a touch too controlled but still present enough to make the response feel full-bodied.



When listening to this pairing, the response sounds calm, allowing for an expressive and open-sounding response with better control over the revealing nature of the notes, allowing the notes to sound as natural as possible with a presentation spread out far and wide, where the upper mid-range pours everything while remaining airy and spacious. Listening to tracks like Gotye's Somebody That I Used To Know and Love Will Come Through, the vocals sounded incredibly real and detailed while yet being open and light without disrupting the tonal balance. In the end, what may have sounded analytical and impartial came off as well balanced and resolved. The bass felt a touch light but more textured.

Rose Technics QT-X

QT-X offers a mid-centric and neutral tone, with a focus on the sub-bass and an overall clean sound. When I first started listening to them, I noticed that whichever source I used changed the quality of the sound without affecting the tuning, which made me understand how versatile they are in terms of technical aspects. The sound is characterized by its cleanliness and transparency, with a particular emphasis in the midrange that gives the vocals and instruments a spacious and well-defined presence. While the graph may indicate that the treble lacks energy and the bass is lean, the tuning of this IEM actually allows the treble to sound expansive and smooth without being dark, and the bass to provide good depth and presence. However, there is a slight lack of warmth and note weight in the mid-bass region that is noticeable throughout the sound signature. Finally, I feel the response has been properly calibrated to sound neutral and accurate, particularly in the midrange, rather than offensive or bright.



While listening to this pair, the response felt slightly less weighted, with a more open-sounding presentation. Despite the fact that the response sounded light and lean, the notes' presentation did not add any metallic or harsh characteristics of the notes that are typical of a tuning like the QT-X. The treble sounded more prolonged and smooth than previously, but the mid-range seemed less front or in your face, with better-positioned singers and instruments sounding expansive and spread out. However, the response sounded confined in the left and right channels while spreading more in the front and rear. Tracks like Kenka by Kujira Yumemi sounded crisp and clear, without sounding hot or sibilant, thanks to voices scaling very high and chimes presented in your face. The bass seemed more powerful and genuine since the kick drums or bass guitar notes decayed organically after hitting.

Tracks​

Millet - Anytime Anywhere
Anri - I can’t stop the loneliness
Kohana Lam - A Few Sentimental
Kohana Lam - Loving Me, Loving You
Uru - Kimino Shiawasewo
Uru - Kamihitoe
Kujira Yumemi - Kenka
Majiko - Kokoronashi
Anly - Sukinishinayo
Kohama Lam - A Few Sentimental
Kohana Lam - Loving Me, Loving You
Miliyah - Kono Yumega Samerumade
Rokudenashi - The Flame Of Love
Yu-Peng Chen - A New Day with Hope
Yu-Peng Chen - Another Hopeful Tomorrow
Yu-Peng Chen - For Riddles, for Wonders
Valentino Khan - Satellite
Kai Wachi - Happier By Now
Jawns - Erotica
ISOxo - how2fly
Kai Wachi - Happier By Now
Weeknd - Popular
YUNGBLUD - When We Die(Can We Still Get High)
Bring to Horizon - Kool-Aid
Middle Kids - Bend
FLETCHER - Leads Me On
Loathe - Aggressive Evolution
The Weeknd - Save Your Tears
Sigrid - Burning Bridges
AURORA - Black Water Lilies
AURORA - Runaway
X Ambassadors - Renegades
Lupe Fiasco - Words I Never Said
Macklemore & Ryan Lewis - Can’t Hold Us
Gotye - Somebody That I Used To Know
Jay-Z - Run This Town
Lady Gaga - Poker Face
Lady Gaga - Just Dance
Ladytron - Ghost
Travis - Love Will Come Through
LINKIN PARK - Somewhere I Belong
DJ Shadow - Six Days (Remix)
Hoobastank - The Reason
Ricky Martin - I Don’t Care
Tool - 7empest
Tool - Vicarious
A Flock Of Seagulls - Space Age Love Song
Zack Hemsey - Vengeance
Elton John - I’m Still Standing
The Moody Blues - Nights In White Satin
Micheal Sembello - Maniac
Guns N’ Roses - Sweet Child O’ Mine
A.R. Rahman - Kun Faya Kun

Conclusion​

To conclude this evaluation, I can happily state that the M15i has the same sound but has been enhanced to the point where the noise, clarity, and, most importantly, cohesion sound make it highly appealing to people seeking the finest clear and transparent sounding dongle available. After listening to the M15i, I felt the same sense of astonishment and exhilaration that I had when I first heard the M15. Congratulations to Questlye for incorporating such a tweak into this generation of the M15. So all in all. I heartily recommend the Questlye M15i, especially at this price range, however I'd want to advise existing M15 customers to test it out before going through the process.