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Head-Fi Review: Questyle M15 - Hi-Fi Sound on the Go

Head-Fi Review: Questyle M15 - Hi-Fi Sound on the Go

 From Head-Fi  By Ryan


- Superbly well balanced neutral and natural sound
- Reference grade technical prowess
- Amazing driving power
- Highly versatile and adaptable to any partners
- Native iOS support
- I wish there was an independent volume adjuster
- Slightly larger in size compared to competitors



Quad amplification engines
Flagship-grade ESS Sabre ES9281AC
Dual Headphone Output Ports(3.5mm Single-Ended+4.4mm balanced)
Two-level gain switch
LED indicators for gain and active bitrate
Low power consumption TOREX power chip
Technical Specs:-
Decoding Parameters: PCM 32-Bit/384kHz, DSD256
Output Interface: 3.5mm single-ended, 4.4mm balanced
Output Power(3.5mm): 11.97mW @ 300Ω, Vout (Max): 1.895Vrms
Output Power(4.4mm): 22.60mW @ 300Ω, Vout (Max): 2.624Vrms
Frequency Response: 20Hz-20kHz±0.1dB
THD+N: 0.0003%
Dimensions: 61.8×27.2x12mm

Test Equipment

IEMs and Earbuds:

  • Etymotic ER4SR (Single BA, 45 Ohm, 96db Sensitivity)
  • Shure KSE1500 (Single Electrostatic 200V, KSA1200 Energizer)
  • Kinera Idun Golden (3BA + 1DD Hybrid, 32 Ohm, 112db Sensitivity)
  • Tripowin HBB Olina (Single DD, 32 Ohm, 110db Sensitivity)
  • VE Asura 3.0 FE SLQ (Single DD, 155 Ohm)
  • VE Monk GONE SPC (Single DD, 32 Ohm)
  • BuduBuds V1 (Single DD, 32 Ohm)
  • FOSTEX T40RP MK3 (Magnetic Planar, 50 Ohm, 91db Sensitivity)
  • Beyerdynamic DT880 (Dynamic Drivers, 600 Ohm, 96db Sensitivity)
  • Windows 10, Foobar 2000 (USB 3.0 Power)
  • LG V50 ThinQ (UAPP USB Exclusive Mode, Bitperfect)
  • Sony Xperia X Compact (UAPP USB Exclusive Mode, Bitperfect)
  • HiBy Music Player App (USB Exclusive Mode)



Questyle M15 marked the progression and evolution introduced with M12, the only Current Mode amplification Dongles to exist now. It is no secret that among over 120 Dongles I owned, the M12 ranks the highest in my book for ESS Sabre unit. I even prefer it more over Apogee Groove and the slew of Hidizs S9 Pro, E1DA 9038 or REIYIN DA-Plus – all of which prime examples of properly tuned ESS Sabre units.

When M15 was released, gleefully I took the opportunity head first to have it delivered to my doorsteps. Full of anticipations and excitement. I know Questyle has great tuning principle and this is a known fact among many audio enthusiasts. Let’s see how does M15 fares in the real world shall we?

PS: As noted above, my M15 has undergone a Firmware update and the entirety of my review are based on it – post FW update.

Build, Functions, Usability​


M15 is a huge Dongle, in fact I daresay it is 3x the size of M12. It is probably the 3rd largest Dongle I ever owned. Apogee Groove being the largest then followed by CEntrance DACport HD. By current standards, M15 is one hell of a solid device construction wise. The traditional rectangular design being simple as it is functional.

Most prominent feature would be the glass faceplate on one side. The glass window would allow us to savor looking at the beautifully crafted internals. Clearly showing generous real estate of components. As I said earlier, M15 is large. The rationale behind this, Questyle opted to go purist route on M15. They forgo the need to downsize in favor of innovation, to ensure that M15 will have all the bells and whistles of a top of the line performer.
Feature wise, despite the size, M15 offers equally simple stuffs like imbedded led lights that can be seen through the glass window. One for power/resolution and another one for High/Low gain. On one side, there’s user selectable hardware switch for gain selection.

However, M15 does not offer any sort of volume adjusters on the Dongle itself. I must admit that I wished it would have include some sort of independent volume adjusters. What I have learned so far, independent volume adjustment does have big role in fine tuning listening loudness. As observed with the likes of Cayin RU6, DACport HD and Lotoo PAW S2 – all of which comes with super refined volume adjusters, the ability to fine tune volume levels has help to elevate music listening greatly – at least in the manner of how I normally use the Dongles – set the volume at Max on the host and let the DAC/Amp regulate the output. Perhaps Questyle can consider this in earnest in upcoming Dongle line-ups.

As for the volume adjustment itself on the host side, like most other Dongles without independent/dedicated adjusters, M15 depends largely on the volume steps resolution of the source. So in order to have fine adjustment, it is necessary to use HiBy Music App (Software Volume Mode) or UAPP Volume Steps. But at least I can tell natively M15 does offer “less jumpy” gain between levels as observed with some other devices.

While M12 came with just 3.5mm SE, M15 stepped up to the current standards of including a 4.4mm BAL Pentaconn port. Balanced circuitry that offers discrete power each channels (L/R) instead of shared GND. This has allowed them to push the power output higher and will work great with power hungry partners.

In alignment with what was already introduced with M12, M15 also offers the latest iteration of Questyle Current Mode amplification. I honestly don’t know much about this technology, so I would not dwell too much talking on it. But what I do know, the Current Mode amp stage of both M12 and M15 plays huge role in shaping up the sonic characteristics they offer.

As with most other Dongles nowadays, M15 comes with female USB C interface for the data link. This will allow for swapping of cables to suit the needs. Included in the stock package, M15 comes with both USB C and iOS Lightning cables. This effectively means that M15 is among the few that has been designed and built from scratch with versatile compatibility to iOS.

Despite being a “larger than normal” Dongle, M15 appeared to be adequately efficient with power draw to the host. With my Sony Xperia X Compact (Android 8, 2700 mAH Battery), M15 was able to clock 5-6 hours of continuous play – driving Tripowin Olina at low gain, USB Exclusive mode UAPP. This is pretty much on par to the competitions like Lotoo PAW S2 and Cayin RU6. Only xDuoo Link2 BAL and HiBy FC5 scored better at almost 7 hours.

Most impressive, M15 is probably the best Dongle DAC/Amp with heat management. Despite the larger size, M15 was able to stay relatively cool even on prolonged sessions.

Sound Impressions​


Questyle M15 is a wonderfully balanced DAC/Amp. From the moment I plugged it in with my Etymotic ER4SR, I was already mesmerized with fluid, crisp, smooth and highly resolving output that does not exhibit any coloration in any frequencies. It is admirably organic and refined sounding. Despite being an ESS Sabre based DAC, there’s absolutely no hint of Pinna Glare or unnatural edgy brightness that is notoriously evident with most ESS devices. The signature of Questyle tuning, it is super clean with immaculate resolved notes and tones – while at the same time managed to avoid the pitfalls of sounding sterile and dry. If I am to turn back the clock over a year ago, when I first tried the older M12, I remember the output was already amazingly clean and pristine – however I did mentioned that M12 (with the old Firmware) has some tendency to emit some dryness. Questyle fixed that for good with M12 later version FW. What I am hearing now from M15, an evolution of that immaculate sound. Something that is exceedingly technical yet musical.

Perhaps if I am to nitpick, on a very personal level I normally prefer a bit more of analogue touch to the output, M15 seems to be not as analogue sounding when compared to CEntrance DACport HD, Ovidius B1 or Cayin RU6. M15 is more aligned with the Hi-Fi sound approach which is favored by L&P W2, HiBy FC5, Colorfly CDA M1 and REIYIN DA-Plus – which means among them all, I can easily say that M15 is the BEST of the crop with that Hi-Fi approach. That effortless dynamics and transients making it such a pleasure to listen to, the overall theme being crispy smooth, resolving and detailed.

On dynamic range, M15 is assuredly a stellar performer. The extensions on both ends nothing short of impressive. What I am hearing from my regular favorites of Shure KSE1500, Etymotic ER4SR and Fostex T40RP MK3 revealed how rich the extensions are. Highly detailed on macro and micro levels. Sub Bass being rich and dense, Treble being sparkly with proper texture, Mids being wholesome and engaging – and keeping it neutral, uncolored while at it. Never a moment I felt that any of the frequency range being emphasized beyond what is realistic.

Technically, M15 is an absolute beast. Just like the predecessor of M12, M15 carried on with that trajectory with some of the very best technical performances I have heard so far. Being critical, perhaps the only caveat that I can point out would be the average sized soundstage which I wished could be a bit wider. In this regard, I would say that the likes of xDuoo Link2 BAL, THX Onyx and DACport HD offers the widest soundstage still. M15 on the other hand is pretty much similar to Cayin RU6 and Lotoo PAW S2, it has breadth of space, depth respectfully spacious but just slightly short on absolute width.

What M15 does offer in spades, reference level of resolution, imaging, speed, details and separation. M15 is a device that will please even the most demanding need for technical indulgence for listening to highly complex music. The better the recording and mastering, the better it gets. For example, with highly complex Jazz composition, I was able to appreciate even the most subtle of nuances – presented with crisp imaging and cleanly defined layers. In fact M15 performed miracles with my favorite duo of Kinera Idun Golden and Tripowin Olina – elevating those two IEMs technically to TOTL level of performances, no joke!.

As I always mentioned, the hallmark of a great DAC/Amp – their ability to synergize with anything. And M15 is one such devices. Be it my super hard to drive Beyerdynamic DT880 600 Ohm and Fostex T40RP MK3, open back VE/BuduBuds earbuds, highly sensitive hybrid IEMs, even legitimate 200v Electrostatic of Shure KSE1500, M15 does it all with such guile and finesse. That’s how a true neutral DAC/Amp should behave – it does not show any specific preferences to what sound curves the paired partners have. It just works

Driving Power​


Questyle M15 is a 2.62 Vrms rated dongle (4.4mm BAL). Despite not being a 4 Vrms device, M15 does have tons of power at its disposal. This is similar to the performances of Ovidius B1, Hidizs S9 Pro and Creative SXFi, the other 2 Vrms devices that offer tons of power to even handle super stubborn magnetic planars.

For my own usage, M15 performed spectacularly to drive Beyerdynamic DT880 600 Ohm with ease. On HiBy Music App USB Exclusive mode, M15 only needed 16/32 volume for proper listening loudness. On my PC it was at 40/100 max (any higher and it would be just too loud for my comfort). Simply put, the sort of performance offered by M15 in this scenario really cemented my belief that I don’t need a dedicated desktop DAC/Amp stack combo. Everything about the sound simply being wholesome and satisfying. No hint of micro jitters or distortion. It’s all about fluid harmonics end to end. I am not hearing any loss of micro details. About the only thing missing, perhaps absolute headroom sense, like 2% less headroom as compare to the output as heard from my iFi ZEN Stack of ZEN DAC V2 + ZEN Can. That 2% is totally negligible. The same can be said for the magnetic planar of Fostex T40RP MK3, one of the most stubborn planar headphones out there now – no sweat for M15.

On the other hand, despite all that power, M15 has also shown amazing synergy with super sensitive and easy to drive stuffs. I am getting super clean output from my Tripowin Olina and Kinera Idun Golden. Pitch black background even on the most silent of passages. This is consistent even on High Gain mode.

Volume Difference (With Etymotic ER4SR, HiBy Music App, USB Exclusive Mode)
SE 3.5mm = 12/32 (Low Gain)
BAL 4.4mm = 9/32 (Low Gain)

I am happy that both 3.5mm and 4.4mm ports shared identical sound quality. The difference only the absolute limit 4.4mm can go which is up to 600 Ohms. However for anything under 155 Ohm the 3.5mm will work as great as the 4.4mm side. Once volume loudness matched, I can’t hear any difference at all. This is simply amazing because I have heard many (if not all) Dongles being slightly inferior on the 3.5mm side, but M15 does not neglect this element. In comparison, the likes of Luxury & Precision W2 and Lotoo PAW S1 practically treated the 3.5mm port like a 2nd class subject.


Questyle M15. All things considered, I am confident that M15 being one of the very few releases for 2022 that can claim 5 stars rating. Sound wise, M15 offered practically everything that I like about sonic performances. The balance of neutral organic timbre, totally uncolored and devoid of any unpleasant edginess commonly associated with ESS Sabre DACs.

M15 biggest strength being superbly versatile and effortlessly fluid in projecting Hi-Fi sound in a compact form factor. Yes it is 3x bigger than M12, but the size is well justified for a truly complete package when it comes to delivering sound quality. If I must be critical, then my only wish list would be an independent volume adjuster – had that been included, M15 would have assuredly been perfect.

Simply put, Questyle M15 has set a very high standard for how a great modern Dongle DAC/Amp should sound. It is amazingly well crafted to be competently technical as it is musical. Mesmerizing every time I listen to it.



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