Questyle M18i

QUESTYLE is one of the well-esteemed audio companies around as they brought forth some of the highly acclaimed audio equipment that are used on both professional and non-specialised side of audio appreciation. Their well-regarded reputation as producers of high quality audio products assures that every product that they release on the market will be solidly built, easy to operate and will have some excellent components sourced from reputable audio solutions.



I previously published a few products from them and all of them are from their M series line-up models which are all portable headphone DAC/Amplifiers also known as USB DAC dongles. And now, what I have here and will be the highlight of this product review is the latest generation of the M Series models, The QUESTYLE M18i.



Unlike the previous models which are more of a standard portable headphone DAC/Amplifiers, this one has some new features that makes it more advanced as QUESTYLE added some of the latest breakthroughs of mobile audio innovation, particularly on wireless technology. And with some added features, this device is relatively a bit larger just to accommodate some functionalities that will deliver a worthwhile audio experience.



The QUESTYLE M18i still shares some similar design language and form factor with the previous M-series albeit it incorporates a screen beneath on its tempered glass panel, an extra USB-C for charging (yeah, this is quite a unique feature) and finally, some physical buttons. The overall frame itself is made of a high quality CNC-milled aluminium alloy that underwent an anodisation and sand-blasting process to achieve its matte-like finish on its surface for better grip, less fingerprint magnet and resistant from light scratches, and like all M-series, it has black colourway with rather minimalist design on its aesthetics.



At the front part where the glass panel was situated, its appears that like M-series, it uses a tempered glass panel provide by Kunlun and beneath of it was a OLED screen panel in which display a simple UI for volume control, gain mode, battery level, sampling rate with its audio signal format and device modes. On the back part, there are no other hardware features aside from the Questyle brand and the brand model print that was etched on it.




On the long side panel, there is a USB-C port (input charging only) that supports USB charging while using the other USB-C port for decoding at the same time which is more convenient in my opinion. And at the opposite length panel, there are some hardware key buttons for volume controls and gain/MFB mode and a power button along with toggle switch for device modes for PC, Mobile and Bluetooth DAC/Amp connectivity as it has an advanced optimisation for power supply for reduced power consumption for each specific mode along with a built-in mic input. The buttons also support some basic media playback controls like play, pause and next via double pressing on playing tracks, and also on calls like answer, reject and disconnect.




The gain mode, we can switch on either low gain more or high gain mode while its volume amplitude rating can deliver up to 60 steps with an incremental adjustment on each level. On the power button, if we press it, it will be on the stand by more which makes the UI print a bit dimmer.



And then, at the side vertical angle part, like most of the previous generation of M-series, it has a dual headphone jack set-up of varying output types, a standard 3.5mm single-ended and a 4.4mm balanced output. And on its opposite side, this is where the USB-C port can be connected to other devices with compatible connectors, like smartphones, tablets, laptops and PCs along with other devices as long as it supports USB audio.



Unlike the top models of the M-Series that uses a flagship USB DAC, The QUESTYLE M18i uses a rather standard ESS Mobile DAC, the ES9219Q which is proven and pretty consistent on its performance particularly on decoding performance and power output. The DAC chip itself is quite efficient as it has a low power that can process up to 32-bit with a two channel stereo output along with its advanced circuitry architecture for improvements of dynamic ranges,frequency filters and sampling modes in tandem with its capable built-in SABRE headphone amplifier.



Like all QUESTYLE products, it still utilises its patented technology which is its vaunted CMA module technology. This one is a type of a SiP module with functional quad audio amplification engines that eliminates negative signal feedback due to better bandwidth, huge improvement of its dynamic signal processing and ultra-low distortion rating will deliver an excellent clarity, detailed and accurate sound reproduction which has a similar peak performance of a Class A amplifier.


As I mentioned before about some of its newly introduced features, The QUESTYLE M18i also includes some wireless connectivity like bluetooth and microphone. The Bluetooth chip of this device is a 5.4 version provided by Qualcomm which improves its Bluetooth Low Energy technology along with improved reliability and stable connection, more efficient on transmitting high data transfer and better energy management for lower power consumption compared to its previous generation. Since this is a Qualcomm component module, it can support advanced bluetooth codecs like apt-X adaptive, apt-X HD, LE Audio and LDAC aside from standard bluetooth codecs like SBC and AAC. This device also utilises an latest generation of Infineon MEMS microphone that supports HD calls with its AI assisted noise reduction technology and noise filter for better SnR, low distortion and better sensitivity matching for high fidelity voice quality.



Another thing is that this device also has a built-in 500mAh lithium-polymer battery whose performance is very underwhelming that it can only wireless bluetooth playback for over two hours on low gain mode and much lesser on high gain mode.


On its product packaging, it has a simplistic presentation and still shares similar content layout with the previous M-series models. Aside from M18i headphone DAC/Amplifier, it also includes a short fabric-sheathed type-C to type-C cable, USB type-C to type-A adapter and paperwork like user’s manual with different languages and warranty card.



The QUESTYLE M18i is a plug and play peripheral device that can support all known major devices on both hardware and software aspects. On the hardware, it's compatible with all known modern computing devices as long as it has a USB type-C connection that supports USB Audio. Another good thing is that it has an Apple’s MFi certification that it can be used across its well-developed ecosystem with its own software and hardware compatibility.


As for its software side, here is the table of lists on its operating system interoperability.


In this review, I will use my Android phones 9 (Android 9.0 up to the 13) and a laptop with a LINUX MINT OS.



The QUESTYLE M18i can deliver a strong power output that can drive some of power hungry cans and IEMs with special drivers that need better amplification to sound properly. With some of its newer components that if it was paired to some overly sensitive IEMs, there will be no worrying about unwanted noise floor distortions.



List of headphones and IEM earphones that will be used on this test.

• LETSHUOER S12 2024
• LETSHUOER EJ07
• LETSHUOER EJ09
• SIVGA ANSER
• SENDY AIVA 2
• 7TH ACOUSTIC SUPERNOVA

As for its tonal performance, it appears that QUESTYLE M18i delivers a bit of a warmish-neutral sound profile as it has a noticeable more textured compared to the previous M15 models which are known for their balanced-neutral type of sound that makes them more ideal tool on audio reviewing.




LOWS/BASS:

This device conveys a more firmness and tactility on the bass response to sound more punchy, more denser and impactful that pairing it with IEMs with more emphasis on low frequency will add more dynamic character. It can deliver a deep and reverberating quality on its sub bass presence that were generated from low-tuned string instruments like bass, guitars, double-basses and octobasses, and also on percussives drum machines and synthesisers.

And on its mid bass, apparently that if it was paired to more neutrally-tuned IEM earphones, it somehow adds a bit more texture as it give more body on deep male vocals as it add richness, resonance and sombre sound but not to the point that it sounds too boomy and authoritative. And also on instruments, particularly on bass-clef ones, bass guitars will have more dusky sound, double-basses sounds more broader and resonant, bass trumpets sound fuller with a more darker timbre and a bass kick drums’ strikes will have a bit fuller and sonorous sound.


MIDRANGE:

As it maintains a neutral presentation, I can certainly pinpoint that there is a little bit of warmth as it adds more depth and richness on vocals and instruments to sound organic as possible while maintaining a clean and detailed sound quality on them. On the sound quality of male vocals, baritones have smooth and rich sound while the tenors have that brassy and ringing quality on their voices, and then, a tender and clear falsettos of countertenors. For female vocals, a richer plushy sound on contraltos, a velvety and coppery sound on mezzo-sopranos, and then, a more satiny and creamy sound on soprano vocals.

About instruments, on strings, a bit buttery sound on guitars, a sensuous and silky sound on cellos and a sweet and softer sound on violins. On the woodwinds, it somehow maintains the clear and light sound on piccolos, a graceful yet brilliant sound on concert flutes, a mellow and rich sound on clarinets and a sonorous and reedy sound on saxophones. The brass instruments, in corresponding order, are full, rounded and sound on trumpets, trombones and horns. As for the remaining instrument type, the percussion ones, a harder and precise sound on snares, as sonorous and full sound on every stroke on field drums, a rich and resonating sound on tom-toms, and a deep and substantial sound on kettledrums. And lastly, the pianos seem to have a balanced tone as they have rich, sweet and clear sounds on them.


HIGHS/TREBLE:

The treble quality on this one delivers a lustre and sheen presentation with sufficient amount of airy enough to highlight the clarity and definition on vocal articulation and a sharper attack of both rhythmic and percussive instruments. If it is paired on some IEMs with a neutral-ish bright sound signature, it somehow adds a sufficient amount of air without emphasising too much on the brilliance section on the high frequency region.

This device somehow adds a bit more brilliance, silvery and shimmer on respective treble-clef instruments; cymbals, glockenspiels and celestas.


OVERALL TECHNICALITIES:

Like all M-Series that I have tested in which are remarkable in terms of technical performance, QUESTYLE M18i is no exception as it also shares those impressive qualities that defines these portable headphone amplifiers. It is capable of projecting a fairly spacious sound field dimensions with a well-layered black background soundscape.

It has pretty excellent on resolution capabilities on how it contrast between macro-dynamics and micro-dynamics as the former will have a more concrete dynamic range as it how it highlights the gradual volume phase from soft and quite levels up to the loudest level on instrumental passages and chorale lines, while on the latter, it is able to show some micro-details, nuances and subtleties in a sonic gradient with likes of notational attack of instruments, vocal ends and reverb tails.


PEER COMPARISONS:

QUESTYLE M15/M15i

• It shares similar design language with the M18i but it has a compact size on its rectangular form factor.
• They don't have an OLED Panel to display the current status but on its tempered glass, we can clearly see its internal parts like circuit board, transistors and ICs.
• It uses an LED indicator to determine its current sampling rate.
• Unlike the M18i, it doesn't have any physical key buttons for volume control and basic media playback control and its toggle switch has a different function as it is used to adjust gain modes.
• It doesn't have a built-in battery, so it doesn't have any bluetooth connectivity at all nor an integration of a HD microphone to receive calls.
• It uses a flagship grade USB DAC chip from ESS, ES9281AC.
• The M15 can process and decode up to 32-bit/384khz on PCM audio and up to DSD256 on DSD format, The M15i is even more capable as it can process up to 768kHz on PCM and up to DSD512 on DSD format.
• It has a dual headphone jack with different output and uses a USB-C as its connector to a host device.
• The M15 has a balance-neutral sound profile with some slight emphasis on high frequency section while the M15i has a tad warmer sound profile.
• It has an excellent technical capability from soundstage size projection up to the pretty resolution on its resolution capabilities although the M15 has a slight edge on micro-dynamics as it has a bit sharper definition on micro-details, grains and nuances.

HIBY W3II

• It has a smaller and slimmer profile compared to the M18i and its frame is made of a high quality PC shell with a built-in shirt clip that makes it lighter.
• It doesn't have any screen but rather a panel with some graffiti designs on it.
• It has an LED indicator for power and bluetooth connection status.
• This device has three button keys for power and volume control, it also works as basic media playback control.
• It has built-in battery with a power capacity of 320mAH but to my surprise, it has longer playback time on both standard Bluetooth formats and advanced Bluetooth codecs as it can play up to 10 hours of continuous playback and a lesser time duration on advanced Bluetooth codec like apt-X HD and LDAC around 7-8 hours.
• It also has a built-in HD microphone like the M18i which also has clear voice quality.
• Aside from its Qualcomm Bluetooth chip, it also has a NFC feature.
• It has a proven Cirrus Logic DAC chip, CS43131 that can process up to 32-bit/192kHz with an output voltage of 1.75Vrms in 98mW of power output.
• It has only one type of headphone jack which is a standard 3.5mm.
• It has a strong software as you can utilise its more functionality via HiBY Blue App.
• It has a warmish-neutral type of sound that makes it a bit closer to analogue profile from the old generation of high fidelity sound.
• It has a pretty decent technical performance from above-average soundstage size, good layering on its soundscape and acceptable resolution capabilities.
• This one is even way cheaper as it was priced around US$40 at the time of its release.

As I conclude this product assessment, The QUESTYLE M18i is definitely a big upgrade from its predecessors as it has some added operationalities that makes it more convenient to use either on a typical plug and play use or in wireless bluetooth transmission mode. For sure that there are some noticeable issues like its playback duration as I’m quite dissatisfied with its performance as it has a rather short uptime of just over 2 hours along with its longer charging time. Aside from its meagre battery performance, I wish that it has some built-in basic EQ just like devices of similar profile. Nevertheless, I will still recommend this device who is looking for excellent and refined tonality with exceptional technical performance, along with support of more advanced bluetooth codecs and a solid build quality that makes it more premium.

The QUESTYLE M18i is now available on QUESTYLE’s official store and you can see the link that I have provided below.

LINK: https://questyleshop.com/products/questyle-m18i


For more QUESTYLE product reviews:

◼ QUESTYLE M15

◼ QUESTYLE M15i


SPECIFICATIONS:

MODEL: QUESTYLE M18i
MATERIAL: CNC-milled anodised Aluminium Alloy
DAC CHIP: x2 ESS ES9219Q
DECODING CAPABILITY: (PCM) 32-bit 44.1 -384kHz/ (DSD) DSD64-256
BLUETOOTH VERSION: 5.4
BLUETOOTH CHIP: QUALCOMM
BLUETOOTH SUPPORTED CODECS: SBC, AAC, aptX,aptX HD, aptX Adaptive, LE Audio, LDAC
CALL FUNCTIONALITY: Supported via Infineon microphone module
BATTERY CAPACITY: 500mAh
HEADPHONE OUTPUT PORT(S): 3.5mm single-ended, 4.4mm balanced
POWER OUTPUT: 28mW at 300 Ohms (4.4mm balanced output)
FREQUENCY RESPONSE: 0.1dB (20hz-20kHz), 2dB (20kHz-80kHz)
THD: 0.0002%
OVERALL DIMENSIONS: 75mm x 35mm x 14.5mm




TESTING TRACKS: ( * = 16-bit FLAC, ** = 24-bit FLAC, *'* = MQA, '*' = DSD, *'= .WAV)

Alison Krauss -When You Say Nothing At All *
Jade Wiedlin - Blue Kiss**
Led Zeppelin - When The Levee Breaks **
Mountain - Mississippi Queen *
Queen - Killer Queen **
Guns N' Roses - Patience *'*
Eric Clapton - Tears in Heaven '*'
Sergio Mendes- Never Gonna Let You Go '*'
Pearl Jam - Daughter **
Roselia - Hidamari Rhodonite *
Assassin - Fight (To Stop The Tyranny)*
Celtic Frost- Visual Aggression *
New Order - Blue Monday *
The Corrs- What Can I do (unplugged version) *
Jimi Hendrix Experience - Voodoo Child *
The Madness- Buggy Trousers *
Metallica - Motorbreath **
Mariah Carey- Always Be My Baby *
Destiny's Child - Say My Name *
Malice Mizer- Au Revoir *
Mozart - Lacrimosa *
New York Philharmonic Orchestra - Dvorak- Symphony 9 " From the New World." *
Eva Cassidy - Fields of Gold (Sting cover)*
Michael Jackson - Give In To Me *
Exciter - Violence and Force *
Diana Krall - Stop This World **
Debbie Gibson - Foolish Beat *'*
The Sisters of Mercy – Lucretia My Reflection**
Suzanne Vega – Luka **
Lauren Christy – Steep *
Ottoman Mehter - Hucum Marsi *
Diana Damrau - Mozart: Die Zauberflöte*


P.S.

I am not affiliated to @Questyle nor receive monetary incentives and financial gains as they provide me a review unit for an exchange of factual and sincere feedback from yours truly.

Once again, I would like to send my gratitude to the Questyle Audio Rep for providing this review unit. I truly appreciate her generosity and trust towards me and other reviewers.

The Questyle brand requires no lengthy introduction. The brand is renowned not only for producing award-winning audio devices like the CMA18 Master and the CMA18 portable, but also for pioneering the patented Current Mode Amplification (CMA) technology.



Current mode amplification (CMA)

It is widely recognized that processing high-resolution lossless audio and driving amplifiers typically requires significant energy. While this poses no issue for AC-powered Hi-Fi systems, it becomes a challenge when designing mobile devices. Questyle’s patented Current Mode Amplification (CMA) technology was specifically developed to address this problem.

As the name suggests, CMA technology processes the audio signal as a current rather than a voltage, using discrete transistors in the circuitry. A Current Mode Amplifier consumes just one-tenth of the power of conventional systems while offering 10 times the bandwidth and dynamic signal processing capabilities, all with ultra-low distortion.

Questyle has also created a range of audio SiP modules, such as the MA2430 chip, which integrates Current Mode Amplification with full-link lossless audio signal processing. It operates with a minimum voltage of 2V and a current draw of only 3mA—less than half the power consumption of a pair of TWS earbuds.

Questyle M18i

Questyle's lineup features three portable USB DAC dongles: the entry-level M12i, and the M15C/M15i, which are enhanced versions of the highly praised M15. Their latest addition is the M18i, a portable USB DAC dongle that stands out from the rest by incorporating its own internal battery and supporting wireless Bluetooth connectivity. The "i" in these models signifies that the device holds an official Apple MFi certification.



Technical stuff

The Questyle M18i is equipped with two ES9219Q DAC chips from ESS for audio decoding. In collaboration with ESS, Questyle has developed the TTA (Triple Decoding Architecture) DAC framework to push the M18i's performance to its peak.

The headphone amplifier is divided into distinct preamp and power amp stages, featuring two CMA SiP modules, which house four Current Mode Amplification (CMA) engines.

The M18i includes a dedicated 16-Core XMOS XU316 USB receiver, offering full compatibility with iOS, HarmonyOS, Android, Windows 10/11, macOS, and PSP gaming consoles. It supports high-resolution audio decoding up to 384kHz/32bit PCM and DSD256 via the USB Type-C input.

Additionally, the device is equipped with a Qualcomm Bluetooth 5.4 receiver, supporting AAC, SBC, aptX, aptX HD, aptX Adaptive, LDAC, and LE Audio decoding. In Bluetooth mode, the M18i draws power from its own battery.

For high-definition calls, the M18i features Qualcomm's cVc Generation 8.0 ClearVoice Capture technology, providing Advanced Noise Reduction to eliminate background noise and ensure clear sound delivery to the user.

Extra USB power input

The Questyle M18i features a dedicated USB Type-C port for power input, allowing you to charge the battery while using the device simultaneously. Once the battery is fully charged, the device switches to drawing power directly from the external adapter. Keep in mind that this function is solely for charging purposes and, unlike FiiO's desktop mode, does not enhance the M18i’s power output.



Non Audio stuff

The Questyle M18i features a rectangular chassis with a minimalist, industrial design reminiscent of the CMA18 portable and M15i. Crafted from CNC anodized aluminum, it boasts a smooth black matte finish, while the front panel is reinforced with tempered glass. Its rounded corners and edges ensure a comfortable grip.

Built with exceptional precision, the M18i exhibits no visible flaws, and its well-integrated buttons remain firm without any wobbling. Measuring 75x35x14.5 mm and weighing just 50g, it is both compact and lightweight, comparable in size and weight to other USB DAC dongles.

Unlike some other Questyle portable DAC/amps that showcase internal components through a transparent glass panel, the M18i features an OLED screen. This display provides essential information at a glance, including volume level, gain setting, battery status, working mode, and input sampling rate.



In use

The M18i offers three operational modes and features four push buttons along with a switch. The switch allows you to toggle between PC, Phone, and Bluetooth modes. The first button powers the device on and off and wakes the screen, while the second and third buttons adjust the volume. The fourth button, a multifunction button (MFB), serves as a gain switch and performs various functions in Bluetooth mode.

In Phone mode, the M18i runs on its internal battery, with the USB port used solely for data transfer, ensuring it does not drain the phone's battery. Similarly, in Bluetooth mode, the device functions as a wireless receiver and relies on its own battery for power.

In PC mode, the USB port handles both data transfer and power supply, utilizing an intelligent power management system that efficiently balances power distribution between charging the battery and supporting system operation based on the host device's current limitations.

Regardless of the mode, you can connect an external power adapter via the second USB Type-C port.

The M18i does not support a companion app and lacks an internal menu for adjusting audio settings or other parameters.

Bluetooth connectivity and performance

When Bluetooth mode is selected, the M18i automatically enters pairing mode and locks onto the highest-quality codec supported by the transmitting device. The active codec is displayed on the OLED screen.

In Bluetooth playback mode, the gain button does not function for adjusting gain dynamically; you must set the desired gain beforehand. Instead, a single press of the button toggles play/pause, while a double press skips to the next track. Rewinding to the previous track is not supported. Additionally, during an incoming call in Bluetooth mode, pressing the button answers the call, double-pressing rejects it, and pressing it again ends the call.

The Bluetooth connection remains highly stable within the same room, and the audio performance is exceptional, particularly with the LDAC codec. The sound quality is so impressive that only careful listening reveals the slight advantage of a wired connection.



Accessories

The included accessories are quite limited and do not justify the M18i’s price point. The package contains only a high-quality USB OTG cable and a USB adapter. Apple users will need to purchase a separate USB-C to Lightning cable, and the premium Questyle protective case is sold separately for $29.99. To enhance the overall value, Questyle should have included both a USB-C to Lightning cable and a protective case at no additional cost.



Power output and noise

Questyle lists the balanced output power as 28mW at 300Ω but does not provide specifications for 32Ω or 16Ω loads. In real-world use, the M18i proves to be quite powerful, easily driving full-sized headphones like the Sennheiser HD660S2, Hifiman HE1000 Stealth, and Meze Audio 105 AER. It is also well-suited for sensitive in-ear monitors, thanks to its virtually silent background and resistance to electromagnetic interference (EMI).

Battery Life

The M18i features a modest 500mAh battery, which provides a maximum of just 2 hours of operation, regardless of whether it is used in Phone or Bluetooth mode. At high gain, the battery level drops from 100% to 80% in under 30 minutes—an underwhelming performance that makes it impractical as a standalone battery-powered USB DAC dongle or Bluetooth receiver unless frequent recharging is an option. Additionally, the battery does not support fast charging and requires two hours for a full recharge.

Out of curiosity, I measured the device’s power consumption in PC mode and found it to be 0.26A with a fully charged battery. Given this relatively high consumption, it’s no surprise that the battery drains quickly.



Audio stuff

The M18i delivers outstanding audio performance, making it one of the best USB DAC dongles for those who prioritize neutrality and transparency. Its frequency response is perfectly flat, ensuring class-leading fidelity and precision without imparting any coloration to the sound.

Questyle has also expertly refined the typically aggressive treble of the ES9219Q DAC chip, resulting in a presentation that is crystal clear and energetic without becoming harsh or overly bright. The M18i excels in resolution and detail retrieval while avoiding a sterile or overly analytical sound.

While it may not offer the rich, organic, and analog-like warmth of some competitors like the Cayin RU-7 or iBasso Nunchaku, the M18i maintains a lifelike and natural sound with minimal digital glare. It won’t add extra warmth or tube-like richness to the music, but it adeptly reveals and enhances the harmonic complexity within a high-quality recording.

The CMA modules deliver an impressive bass performance, characterized by wide dynamic contrast, strong impact, and excellent technical precision. The bass is fast, tight, and well-controlled, with outstanding layering and separation. While the textures aren't overly visceral or weighty, they remain rich and engaging, avoiding dryness while maintaining elasticity and a lush presentation. The M18i offers a well-balanced performance—technical enough to satisfy discerning audiophiles while also delivering an exciting and engaging sound for modern music.

The midrange and treble are presented with remarkable clarity, strong presence, and excellent articulation, without compromising harmonic richness. The textures are sufficiently weighty, aligning well with the low-end, ensuring that higher-pitched instruments don’t sound thin or artificial. The timbre remains natural, free from metallic artifacts or clinical harshness.

The M18i delivers an impressively spacious soundstage that maintains a natural presentation, complemented by top-tier imaging and separation. While it may not be the most holographic DAC dongle available—the iBasso Nunchaku slightly surpasses it in this regard—it still provides an immersive and expansive experience with excellent depth layering.

In conclusion, the Questyle M18i pairs well with all types of earphones, including brighter ones, and complements all music genres. You can confidently use your most high-end earphones without the M18i being a limiting factor. However, keep in mind that its highly revealing nature makes it rather unforgiving of poor recordings.



Comparison with the FiiO BTR17

The FiiO BTR17 ($199) is the brand’s flagship USB DAC dongle, featuring an internal battery and Bluetooth connectivity, much like the M18i. While these two devices share several similarities, they also have distinct differences. The BTR17 is priced $149 lower and comes with a leatherette protective case as part of the standard package.

Slightly larger and heavier than the M18i, the BTR17 justifies its size with a 1.3” IPS color display, a multifunctional volume control wheel, and a higher-capacity battery that provides 7-8 hours of playback.

Although their core functions are similar, the BTR17 offers a true desktop mode that bypasses the battery entirely and boosts power output to 650mW*2/32Ω. Additionally, it is compatible with the FiiO control app, allowing users to fine-tune audio settings such as digital filters and utilize a 10-band lossless PEQ.

In terms of sound, the BTR17 maintains a neutral tuning but leans towards a brighter presentation, emphasizing treble more than the M18i. While it may have a slight advantage in technical performance and detail retrieval, it also sounds more clinical and sterile in comparison. Both devices excel in bass impact and dynamics, but the M18i delivers a fuller, more fluid, and slightly more organic presentation. The BTR17, on the other hand, has a more digital and artificial timbre but is also more transparent and clean.

Conclusion

The Questyle M18i is a fantastic USB DAC dongle, delivering outstanding wired and wireless performance. Its unique CMA modules expertly manage dynamic range, providing desktop-level driver control and impressive bass response.

Built with quality, the M18i is compact and lightweight, featuring a separate USB power input for added flexibility. However, its limited battery life and lack of customization options prevent it from being truly perfect.

That said, its exceptional sound quality more than makes up for these shortcomings. Instead of focusing on battery limitations, it’s best to see it as a high-performing USB DAC dongle with the added perk of running for a few hours without external power.

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The review sample was kindly provided free of charge in exchange for an honest review. I don't use affiliate links. The price of the M18i is $349 and you can buy it from Questyle online shop.

Disclaimer: For various Google indexing reasons, most parts of this review have been processed with an automatic paragraph rewriting tool. However it reads exactly the same as the original content that is available in my website.

This is super short and to the point…

Sound: Really Great — Somewhere between the DC Elite and Kensei (in tonality and soundstage…more immersive than both).

Battery: Horrid — 1-2 hrs tops.

Power Management: Pitiful. I’ve owned two units and they both would not let me power the device off 90% of the time. The other 10% I could only do so by “interrupting” the circuitry by unplugging something, or toggling source switch.

Performance Otherwise: Terrible. There’s a half-second delay INTO the music every single track, regardless of device. Maybe a firmware update will help, but, again, I’ve owned two of these brand new and they both did the same thing on iPhone, iPad, or MBP (iTunes or Tidal).

I feel like most reviews were excited about the sound initially, as I was, and I could ignore battery life as I use it plugged in the vast majority of the time. But being a listener of a lot of prog rock/metal/alternative, to miss the first jarring notes of every single tune kinda made me wanna throw it across the room. I want to like Questyle, I really do. But their “18” portable series of products have seriously missed the mark in execution. The fact it’s already being discounted by $50 on Amazon, and few other retailers, is not a great sign this early into the release.

Review Of The Questyle M18i ​

Introduction​

Questyle has long been a significant force in the audiophile community, particularly with its portable audio solutions, which include the well-regarded M series and last year’s CMA18P. Having followed the company closely since 2021, I have developed a deep appreciation for their offerings, especially the M15. The moment I first heard the M15, I was captivated by its aesthetically refined design and its ability to deliver a powerful yet highly analytical sound, thanks to its ESS Sabre DAC chips and Questyle’s proprietary in-house amplifier technology. That experience led me to purchase it immediately, as it stood out not just for its sonic excellence but also for its elegant and minimalistic build. Over the years, Questyle has introduced several iterations of the M series, each refining their signature approach to high-fidelity sound. However, for the first time, they have introduced an entirely new device within the M series lineup—the M18i. The reasoning behind its name remains unclear, as there is no preceding model called the M18, but what truly matters is the innovation it brings. Fortunately, I had the opportunity to acquire an M18i for review, and before diving into its performance and capabilities, I would like to clarify a few important 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 “M18i”
*Finally, I will only evaluate the M18i based on its performance, even though I will explain how it feels and seems physically and aesthetically.
*Please understand that all opinions expressed in this review are my personal perspective and are not intended to offend anyone’s beliefs or experiences. Therefore, I kindly request a respectful and thoughtful approach to this review, even if it differs from your viewpoint.

Technical Specifications​

Now, being the first of its kind from Questyle, the M18i boasts several features and specifications that set it apart from its peers in the segment. However, these features are irrelevant when it comes to the different form factors and what exactly the M18i packs under the hood.

As for the technical specifications, the M18i utilizes the latest dual ESS ES9219Q chips, and the entire board is powered by a 16-core XMOS XU316 processor, which enhances compatibility with a wide range of devices. Additionally, the M18i employs a professional TTA (Time-Tuned Audio) triple-decoding architecture, ensuring pristine audio reproduction. This advanced decoding process guarantees that every nuance of the original recording is preserved, providing listeners with an authentic and immersive sound experience.

At the heart of the M18i lies Questyle’s globally patented “Current Mode” SiP (System in Package) module, which is a feature found in all other Questyle products. This innovative technology achieves an ultra-low total harmonic distortion (THD) of 0.0002%, delivering exceptionally clear and accurate sound. Just like the M15 series and CMA18P, the M18i also offers both 3.5mm single-ended and 4.4mm balanced headphone outputs, catering to various user preferences. Furthermore, it features a manual gain control, a feature that I truly appreciated when I owned the M15. This allows users to fine-tune the output to match their specific headphones and listening preferences.

For enhanced user convenience, the M18i features a dedicated slide toggle switch that seamlessly switches between PC, Bluetooth, and Phone modes. When using this feature, there are several aspects that are reasonable to consider, given that it has a built-in battery.

Firstly, when the M18i is in Bluetooth mode, it utilizes its own battery when connected to any compatible device. However, when it’s in PC Mode, it transitions from battery mode to the supplied power mode from the PC or Mac. This allows the device to draw power directly from the connected device and simultaneously charge.

It’s important to note that when connected to a smartphone with PC mode selected, the M18i will drain the battery of the connected device.

Another notable feature is the integrated Infineon flagship microphone chipset in the M18i, which enables high-definition voice calls. Advanced noise reduction technology ensures clear and uninterrupted communication. Additionally, it’s equipped with Qualcomm’s cVc Generation 8.0, featuring ClearVoice Capture technology. This technology helps suppress environmental noises and provide clear sound to the user during calls.

Further Information​

Below is a table that provides further details about the M18i:



Compatible Devices

Coming to compatible operating systems, Questyle supports almost every device I can think of. Below are the mentioned devices:

• Android Phones and Tablets: Supports devices running Android 5.0 or later.
• PC Systems: Supports devices running Windows 10 version 18.3 or later.
• As for the Apple devices, the M18i is Apple MFi (Made for iPhone/iPad) certified, it guarantees seamless integration and optimal performance within the Apple ecosystem, which also includes Macs.

MFB or Multifuction Button​

The multifunction button offers a wide range of functionalities, including a gain switch that enables users to transition from standard gain to high gain settings for demanding headphones or earbuds. However, this feature is only accessible when the device is in phone or PC/Mac mode. Below are the specific functions that the button caters to:

• Adjusting Gain: Press and hold the gain adjustment button for two seconds while the toggle switch is in the PC/Mac or Phone mode position.
• Entering Bluetooth Mode: After sliding the toggle switch to Bluetooth mode, press and hold the MFB button for two seconds to initiate pairing.
• Play and Pause: Single-click to play and pause the track.
• Move to the Next Track: Double-click to skip to the next track.
• Answering and Rejecting Calls: Single-click to answer a call and hang up, and double-click to reject a call.

Design, Aesthetics & Packaging​

Build & Dimensions ​

Regarding the build quality, it is noteworthy that the M18i utilizes the same high-quality CNC anodized aluminum alloy employed in the CMA18P and M15 series, as well as many of their portable products. This alloy ensures durability and aesthetics.

The M18i’s body is entirely encased in metal, with the exception of a small screen with the tempered glass on the front just like the M15 series, though I am not sure whether there is a aluminum panel below the glass or not.

In terms of dimensions, the M18i measures 75mm x 35mm x 14.5mm. This makes it 44.5% larger than the M15 series and approximately 57.75% smaller than the CMA18P. However, it is important to note that these measurements are in volumetric units.

The device’s control panel features four buttons, toggle switcj and a microphone strategically positioned on one side, each with a distinct function(from top to bottom):

• Microphone: for picking up the voice during the call.
• Power button: Activates the device.
• Volume up button: Increases audio volume.
• Volume down button: Decreases audio volume.
• Gain switch & multi-function button: Adjusts audio gain and additional functions.
• Slide toggle 3-step switch: Switches between Bluetooth, PC, and Phone modes.

One notable feature of this device is the presence of two Type-C ports, each serving a distinct purpose. The upper Type-C port, located near the high defination OLED screen, facilitates data transfer via the OTG connection. Conversely, the lower Type-C port, situated near the headphone jacks, on the opposite side of the button panel, is designed for charging while simultaneously connecting to a power source, particularly when using the device with a smartphone or DAP.

The OLED screen primarily displays essential information, including:

• Sample rate
• Mode indicator (USB, Bluetooth, or PC)
• Driver connected indicator
• Battery indicator
• Volume indicator
• Decoding indicator (PCM or DSD)
• Charging indicator (active during charging)
• Gain indicator

Upon entering Bluetooth mode, the screen displays a different interface, although it retains a similar visual appearance. The decoding and mode indicators are replaced by Bluetooth codec and bit rate information where the sample rate is situated below the bluetooth codec and before the bit rate, presented in a distinct format.

The bottom of the device houses both a 3.5mm and a 4.4mm audio jack, while the rear panel bears engravings indicating about the M18i model, consistent with Questyle’s product line. And when it comes to the cable connection it can support both lightening to type-c connection aside from type-c to type-c.

Form Factor & Looks​

In light of the Bauhaus design philosophy, aside from the elimination of the transparent tempered glass, the device retains the sleek and minimalist design, emphasizing reliability and confidence. This is particularly evident in comparison to its other devices, despite still having a tempered glass. The design exudes a refined and perfect aesthetic, particularly with its simple tone approach and matte black color scheme. I can concur that such an attractive and pleasing appearance would appeal to numerous audiophile setups, potentially prompting individuals to incorporate it into their desktop environments.

When used with other devices, the device stands out more prominently than the M15 series used to with my setup. This is primarily attributed to the integrated screen and larger size, which give it a subtle yet bold visual appeal. The form factor also facilitates convenient usage, resembling the M15 series despite its larger size.

Packaging​

Similarly to the device’s emphasis on simplicity and minimalism, the packaging is an enjoyable experience to anticipate when opened, as it closely resembles the experience I had with the M15, which I believe is an excellent decision for a minimalist device with a legacy to uphold. While I still have some contemplation that Questlye may have included a leather case and an additional cable for future-proofing purposes, which would have cost an additional $100, I believe it is reasonable. The packaging includes a Type-C female to USB Type-B adapter, a Type-C to Type-C OTG cable, and manuals. Devices that utilize the Lightning port will require a Lightning to Type-C OTG cable to be purchased directly from Questyle or use any other Lightening to Type-C OTG cable that is MFi certified.

Usage ​

The M18i has a sleek body and bears a strong resemblance to the M15 series, although it’s slightly larger in the hand. There were also some visual changes on the screen when I plugged in a balanced plug and a single-ended plug. When using the single-ended port, a visible headphone icon appeared beside the volume indicator, and it changed to a balanced icon when using the balanced port.

However, my usage with the M18i encountered some other issues, primarily related to the battery. Honestly, it’s quite noticeable.

Battery​

So, as mentioned earlier, the M18i battery has a 500mAh capacity. During my testing, I was able to get approximately 1 hour and 50 minutes to 2 hours and 5 minutes of battery life, regardless of whether I was using Bluetooth mode or phone mode.

In phone mode, during my initial testing, it took an average of 12 minutes to deplete 10 minutes of battery. I’ve included the exact step-tesing below.



Although after my second testing session, I noticed that the battery life had been extended by 6 minutes. However, with more cycles, the battery life was capped at 2 hours and 5 minutes, considering the factors like the drivers I used and the inconsistent volume.

All my testing was conducted at high gain with the volume range set from 13 to 17 steps through the balanced output.

Regarding Bluetooth testing, I didn’t notice any significant difference in battery depletion. However, I was able to use the M18i for a longer duration of time with Bluetooth enabled and the LDAC codec.

Additionally, when I first charged the M18i to 100%, the battery level displayed on the device wasn’t consistent. For instance, the battery level decreased from 100% to 98% in less than a minute. Furthermore, while connected to Bluetooth, the device I connected it to showed 90% battery, while the M18i indicated 94%.

When it comes to charging the device, it took approximately 2 hours to charge from 0% to 100% at a current of 1 A and a voltage of 5 V. The device can simultaneously charge and run on battery power when connected to any of the devices.

Another factor to consider is that regardless of the device M18i is plugged into on PC mode, it will not only drain the battery of the connected device but also charge itself, regardless of the proprietary charging port.

Connectivity ​

On LDAC, the signal strength was consistent to over 25-27 meters without any walls in between. However, when I moved to another room, which I believe was approximately 10 meters away from the connected device, the signal began to drop.

On the other hand, AAC consistently maintained a strong signal throughout the duration of my usage, even when I reached the farthest end of my house. The connection stability was notably better when passing through three to four walls compared to when I was using LDAC.

These observations are quite reasonable and do not indicate any issues with Bluetooth connectivity. Therefore, there were no problems with the connection.

The gain setting cannot be changed while the device is in Bluetooth mode. It can only be changed when the device is in phone mode or PC mode. Before toggling to Bluetooth mode, check the current gain setting.

Now, let’s talk about the wired connection. There weren’t any issues except for the cable’s limited flexibility. This can be a positive or negative aspect depending on individual preferences. Personally, I would have preferred a more flexible cable.

Regarding noise, I’ve never experienced any hissing or noise from any of their devices, including the M18i. I was amazed by the drop-dead silence when I connected the IEMs or headphones.

Convenience ​

Now, as I mentioned earlier, this is essentially a larger version of the M15. Eventually, I realized that the M18i’s grip and feel on my hand felt more comfortable than the M15’s. Although the body is slightly bulkier and heavier, it felt more like a portable DAC/amp rather than a dongle.

Moreover, I didn’t notice any significant difference in convenience when I carried the M18i in my pockets or bag compared to the M15. However, I do feel that the M18i’s non-transparent glass will be more prone to visible scratches.

But as far as convenience go, this is a really great device.

MFB & Features​

As mentioned under technical specifications, I’ve clarified the action of the MFB button and all other buttons when pressed or toggled. In my usage, I never encountered any issues with the button’s position. The first button is the power button, and the last button is the MFB button, so navigating through all the buttons was quite easy.

All buttons have a single purpose, except the MFB button. However, the MFB button can only be used as a gain button when the device is in phone or PC mode. In Bluetooth mode, it can be used as play, pause, skip track, pick or hang up a call, and even reject a call. Additionally, under Bluetooth mode, the gain settings can be changed.

Also, when in Bluetooth mode, a telephone icon appears in the center of the screen whenever a call comes through or a call is made, visually alerting you about the call.

Now, when you press and hold either of the volume buttons, the volume increases or decreases incredibly fast, but it doesn’t allow you to navigate through the playlist.

In Bluetooth mode, you can only skip tracks, but you can’t play back the last track, which limits the usage and convenience, but it can be quite adaptable.

The toggle switch isn’t actually a button, so I don’t mention it as one, but sliding it through is really satisfying.

Now, apart from the buttons and toggle switch, there’s a microphone that I believe works exceptionally well when speaking into it. The quality of the voice is significantly better compared to a boom mic, as the surrounding noise is substantially reduced when I’m on call, which is easily noticeable.

Drivability ​

I had no drivability issues with either of my IEMs or headphones during my tests, although my possessions may be questionable when I share my evaluation here.

Well, I believe that when I listen to my Prestige LTD at high gain and on 15 steps of volume, it provides more than enough power to drive it. At 20 steps, my K361s were well-energized. Therefore, I conclude that most power-hungry devices can be powered through it, but the battery consumption will vary depending on how power-hungry or efficient the IEMs or headphones are when using Bluetooth mode or phone mode.

Sound​

Sources and Drivers​

The sources and drivers I used to evaluate the M18i are mentioned below:

Sources

• LG G8X
• FiiO M15S
• Apple iPad Air 5th Gen
• Macbook Air M2

Drivers

• Thieaudio Prestige LTD
• AKG K361

​

Overview ​

The M18i delivers a warmish-neutral sound signature that enhances a rich, vibrant, and lively response. Questyle has offered a unique take, evident in the M18i. The dynamic quality and the completeness of the notes are striking, creating a refreshing yet nostalgic experience.

The vocals and instruments are beautifully expressed throughout the presentation. The notes exhibit great contrast and richness, resulting in a detailed and clear sound. Given the holographic stage and the exceptional resolution of the notes, each note stands out distinctly, making it effortless to discern.

The overall presentation is revealing and dynamic, with the bass notes particularly pronounced. They are fast and impactful, while the highs sparkle and shine prominently.

The midrange is properly elevated and centered, giving it a prominent and full sound. The notes have the right weight and balance, which effectively makes it sound fuller and more complete.

My overall experience with the M18i has been incredibly engaging and surprisingly wholesome, thanks to the enhanced tonal balance and natural sound.

Comparisions​

FiiO M15S

Honestly, what sets the M15S apart from other DAPs in its price range is its transient response. Every note it reveals is exceptionally clear and mature-sounding. While the transparent sound and well-resolved approach may give it a neutral and analytical tone, I find the tonality to be just right for most of my daily drivers.

One of the M15S’ most impressive features is its ability to provide a consistent and enjoyable listening experience, even when used as my primary source of music. However, some listeners prioritize the sound quality of the drivers over the source’s output. Regardless, the M15S’ smooth texture reproduction sets it apart from other DAPs.

Although my personal experience since last year has occasionally led me to switch back to my other DAP to retain that engagement from the M15S for me, I still prefer it over any other device for delivering clear, transparent, and authentic sound. However, I am intrigued to compare the M18i to the M15S.

Now, when I listen to the M18i, the response sounds vibrant and rich in terms of warmth and natural tonality. In contrast, I find the M15S more spread out and wide-sounding. The M18i, on the other hand, has a holographic and intimate quality that enhances the visibility of delicate notes with improved characteristics and contrast. The vocals and instruments sound more vibrant and sparkling with an intimate presentation compared to the M15S. Overall, I would say that while the M15S has a mature and refined sound, the M18i is more vibrant and engaging.

Sony WM1A

WM1A has been my go-to DAP for pleasure listening for the past two to three years, and it seems like it might be my forever companion. It’s not just because of its offline operating system, which never requires any debugging, but also because of its natural yet revealing sound.

The first time I tried it with my Monarch MKII, I was astounded by the sound quality and immediately decided to purchase it. The same applies to other IEMs I’ve tried with it, particularly my cherished Prestige LTD. The magic it conjures up in vocals and instruments, the exceptional stage and separation, and the remarkable resolution are simply incredible, considering it’s a warm-sounding DAP.

The synergy between the drivers works almost seamlessly with every driver I use on WM1A. For me, it’s an all-rounder DAP that I can’t resist listening to when I’m relaxing or when I have a temptation to hear musical reproduction that heals my mind and soul. I’m sure every WM1A user can relate to what I’m trying to convey here.

However, knowing that the Questyle products tend to have a more analytical and neutral sound, let’s see how the M18i compares to WM1A.

Now, the M18i sounds quite different from the WM1A, even though the M18i has a warmish tone. The reason for this is that the M18i’s response is immersive, unlike the large, spacious, and airy presentation of the WM1A. I believe that the notes have a softer, yet more rounded presentation, whether they’re vocals or instruments. Overall, I think the detailed and contrasty presentation of the M18i makes it more revealing and analytical sounding. In contrast, the WM1A is more balanced and soothing to listen to than the M18i.

Questyle M15, M15i and CMA18P

Despite their unique qualities, almost all three products—the M15, M15i, and CMA18P—share a common characteristic: their exceptional clarity and detail retrieval. However, the CMA18P stands out from the M15 series in terms of its ability to effectively produce better staging, layering, and separation in sound output. Regardless of the genre or type of music I listen to, or the type of IEMs or headphones I use, all their products consistently deliver a clear and fluid sound experience.

Furthermore, I have personally tested all their products, and I can confidently say that they eliminate all noise, making it virtually impossible to distinguish even with highly sensitive drivers.

Before the comparison of these products, it’s crucial to understand that this information is based solely on my personal experiences and limited notes from the products I’ve tested. I don’t expect everyone to agree with every aspect, but I genuinely want to offer my honest assessment and acknowledge these products. My objective is to be accurate and transparent while refraining from any confusion or oversimplification. This way, people can gain a much deeper understanding of M18i.

The M18i offers a distinct sound signature compared to the M15 series and CMA18P. While the M15 series delivers a more neutral and analytical sound, the CMA18P provides a richer and more refined tone. Notably, the M18i excels in revelation and fullness in the notes, surpassing the M15 series in this regard. However, the CMA18P falls short in terms of warmth and wholesome presentation, lacking the M18i’s fullness. In summary, the M18i stands as a unique and exceptional offering from Questyle, setting it apart from both the M15 series and CMA18P.

Verdict ​

Questyle has once again delivered an outstanding portable DAC/AMP with the M18i, staying true to their reputation for exceptional hardware and sonic expertise. This DAC/AMP takes things a step further, offering a premium audio experience in a compact and elegant form factor.

While the M18i prioritizes performance and sound quality, its battery life may require some consideration for extended portable use. However, for those who primarily use it as a desktop DAC/AMP, this is hardly a concern. The addition of Bluetooth enhances its versatility, making it a convenient feature rather than the primary focus.

If you’re seeking a dedicated Bluetooth DAC/AMP, there may be other options better suited to that need. But for those who value top-tier sound in a refined and portable design, the M18i is an exceptional choice. It has truly impressed me, and I have no doubt that many others will feel the same.

thaslaya's star rating system:
☆☆☆☆☆ - Fantastic!
☆☆☆☆ - Recommended
☆☆☆ - There are buyers but not for me
☆☆ - Can't see the appeal
☆ - Product is a failure

Disclaimer:
This product was sent to me by Questyle in exchange for my honest and impartial review. I recieve no compensation and all thoughts and opinions are my own. A special thank you to Vivian for coordinating this unit for review.

Non-affiliate product link for those interested: https://questyleshop.com/products/questyle-m18i

There is also a 10% discount offer for the first 100 units purchased.
Code: DPDV38N6J07R

Gear used:
● Samsung Galaxy s25 Ultra
● HiBy R1
● Softears SP01
● Various DAC/amps
● Various IEMs

Source:
● Listening was done through Amazon Music HD or Ultra HD.

Introduction:
In December 2012, Questyle was founded in Shenzhen, China, focusing on the research and development of high-tech, lossless audio products. Their mission is to help music lovers solve technical problems and break free from restrictive environments, offering an immersive audio experience simply. Since their establishment, Questyle has obtained over 50 patents and won more than 40 international awards, including the CES Innovation Award, iF Design Award, VGP Lifestyle Award, and more. They are well known for both their desktop and portable DAC/amps, such as the CMA15, CMA18, and the M15 series. Questyle's most recent portable release is the M18i. This boasts a dual DAC chipset, lossless audio, and support for the latest Bluetooth 5.4. It is currently available for $349 on Questyle's site and other retailers. Let's break down this exciting new product and see how it performs.

Unboxing and build quality:
The M18i comes in a very small and simple box. Unboxing is straightforward and the contents include a USB-C to USB-C cable, a USB-C to USB-A adapter, and the unit itself. A case is available but unfortunately must be purchased separately, which is disappointing considering the unit's high price. The M18i is constructed of black CNC-anodized aluminum alloy. The device is fairly small, measuring 75 by 35 by 14.4 mm. It has a decent weight balance, premium build quality, and a minimalistic style that looks very classy and elegant. I must admit that I like the see-through style of Questyle's M15 series, but the M18i does look much sleeker and more elegant. The unit's face is made of glass with a small embedded LED screen, and the back features the company and model names. The screen displays information such as the mode, streaming bitrate, battery charge, volume, and gain levels. There are 3.5 mm and 4.4 mm outputs and two USB-C ports: one for data transfer and one for charging. There are also some buttons on the side, which I will discuss in the next section.

Technical information and features:
●Compatible Operating Systems: Android 5.0 or later, Windows 10 version 18.3 or later, iOs systems, macOS systems
●3.5 and 4.4 output Output Power: 28mW @3000 (4.4mm balanced output)
●Dual Ess flagship ES9219Q USB DAC chip
●Apple MFi certified
●PC/BT/PHONE Modes
●Qualcomm Bluetooth 5.4; supports AAC, sBC, aptX, aptX HD, and aptX
Adaptive.LDAC,LE Audio
●Infineon flagship microphone, supports HD Calls with Advanced Noise Reduction Technology
●Battery Capacity: 500mAh
●Decoding Capability:
PCM44.1kHz-384kHz(16/24/32bit)
●Frequency Response: +0.1dB
(20Hz-20kHz);+2dB (20Hz-80kHz)
●Low and high gain toggle button
●60 steps of volume

Unfortunately, the M18i is pretty light on features. There's no bass boost, EQ, digital filters, or app support, though it does offer three modes: PC, phone, and Bluetooth. Turning on the device is done with a simple tap of the power button. However, powering off the unit is a little strange. You need to hold the power button for about three seconds and then let go. That last bit is important because if you don't let go, it will perform a reset after holding the button for about eight seconds. It's just a bit strange to me that holding the power button doesn't simply turn the device off after a few seconds. There are a few other quirks as well, including the fact that you can't power the device off while it's charging. You have to wait for it to turn itself off after a few minutes of being idle. The buttons are pretty straightforward. There's the aforementioned power button, a gain/multifunction (MFB) button, volume up and down, and the switch to change modes. When using Bluetooth, one press of the MFB will pause/play, and a double press will skip to the next track. Unfortunately, there is no previous track function. There is also a slight input lag, which can be annoying. Regarding connection stability, I was able to travel about 30 yards from my phone without issue, and I did not notice any signal drop due to walls.

Battery life and power consumption:
With my devices in airplane mode and the M18i set to PC mode, I let my library play at a medium-high volume with high gain enabled, while limiting unnecessary screen interaction. Here are the battery drain results after one hour:

~30% on HiBy R1 through 4.4 and ~28% through 3.5.

~8% on Galaxy S25 Ultra through 4.4 and ~7% through 3.5.

As you can see, the M18i performed better with the S25 Ultra, which is to be expected. However, I was pretty surprised at just how much juice it drained on the R1. It might not be the best pairing with cheaper DAPs, but that's not necessarily a deal breaker. In Bluetooth mode, the battery only lasts about two hours using the 4.4mm output and high gain. In phone mode it didnt fair much better, only lasting a little longer. In my opinion, this is pretty terrible and almost unacceptable for a device priced at $350 in 2025. For a product boasting both lossless audio and the latest 5.4 Bluetooth capabilities, why would Questyle choose to utilize such a small 500 mAh battery? In fairness, the sound quality through Bluetooth is as good as when wired, and the battery can be charged while in use from the separate USB-C port. But that doesn't excuse the poor battery life, and I don't really want to have to carry an additional portable power supply for the M18i if I'm using it in the go. It also doesn't charge very quickly, at just over two hours from 0-100%. I would imagine a 1:1 ratio of charging to use time is less than ideal, and in practice, it felt pretty bad.

Comparisons:
●Qudelix T-71 ($229) - This is an interesting DAC/amp that I received for a trial period. This and the M18i have similar build quality with a metal casing and an LED screen. The T-71 is larger, but both weigh about the same. The M18i has a more refined aesthetic and feels more premium. Both have internal batteries, but the T-71's lasts much longer. The M18i does include a separate USB-C port for charging. The T-71 has 2.5mm and USB-C outputs, which are not available on the M18i. When it comes to features, the T-71 wins hands down. It has full app support, a built-in EQ, seven digital filters, and a slew of other features like 7.1 surround sound. The M18i does have Bluetooth functionality, unlike the T-71, but the battery life leaves a lot to be desired. For my sound comparisons, I utilized the linear phase filter on the T-71. The M18i sounds much more dynamic and has a certain fullness to its presentation. The soundstage is deeper, too, and they have a similar width. Overall, the M18i is more musical with added bass rumble and extension, but it is also a little more accentuated in the treble, so there is somewhat of a V-shaped presentation. The T-71 does sound a bit flat in comparison due to its more balanced and even-kiltered tuning, but it also has a slightly unnatural quality to the sound at times. The M18i accentuates piano strikes and the bow draw of string instruments exquisitely well, as if you're at a live performance and can hear the passion of the performers. It really gives me that goosebumps feeling when there's an emotional connection to the music that the T-71 doesn't quite have. It is good quality, just not emotionally charged like the M18i. From a purely sound quality point of view, I definitely prefer the M18i, but for the overall package and value, the T-71 is a much better bang for buck, especially for those who enjoy EQ.

●HiBy FC4 ($79) - The FC4 is smaller and does not include a screen. It also does not include any bells and whistles; it is basically plug and play. The M18i has more functions like a gain toggle, an internal battery, and Bluetooth capabilities, which make it the much more versatile option. As for the sound, the M18i's bass sounds a little fuller and better resolving, with deeper sub-bass extension and more reverberation. The FC4 does have more mid-bass impact and punch, though. It also accentuates the treble a bit more, and cymbals sound a little splashier in comparison. The M18i has a slightly more natural timbre and tonal accuracy, especially with string instruments. The FC4 has a wider soundstage, but the M18i has much more depth, dynamics, and separation, and sounds more natural. Vocals on the M18i are a bit more engaging and forward, with a little more life and soul. The M18i is hands down the better-sounding device, and the phone and Bluetooth modes add some versatility. However, the cost of the M18i is quite high—over four times the price of the FC4. Diminishing returns are real, and the difference in sound quality between the two isn't enormous, but I do prefer the M18i.

●Snowsky Retro Nano ($59) - These two have quite a difference in price and build quality. The M18i has a much more premium design and build and feels very nice in hand with a decent weight. The Nano is small, with a retro design and is mostly made of plastic. It feels pretty cheap in hand, but it does have a screen and a replaceable battery. Both have three modes (PC, phone, and Bluetooth), but the Nano also includes built-in EQ and FiiO app support. The M18i has better Bluetooth quality but a shorter battery life. Like the gap in their prices, the sound quality of these two is quite different. The M18i has better bass extension, rumble, and resolution. Instruments and vocals are very natural and never sound strained. The difference in the depth of the soundstage is striking, with the M18i being the clear winner. It also offers better dynamics, separation, and layering, and a more natural timbre. Overall, the M18i offers a more mature sound with better technicalities and better performance across the board, which is not really surprising. Yet, I would argue again that diminishing returns do not necessarily justify the vast price difference. The Retro Nano is a fun, feature-packed little device; however, the M18i's sound quality is clearly superior in just about every way.

●iFi GO link Max ($79) - The Max is very basic and about as simple a dongle as you can get. It has a nondetachable cable and no buttons or extra functions. To its credit, it is very compact, has a decent metal build quality, and comes with both 3.5mm and 4.4mm outputs. The M18i is better built, has a premium aesthetic, and is quite a bit larger, which is not surprising considering it has an internal battery. As for the sound, the Max is more laid-back and smooth, whereas the M18i is very much not. Compared to the Max, the depth of sound and the dynamics of the M18i are off the charts. The difference in orchestral music is like sitting in the back of a concert hall versus sitting on the stage next to the performers. The instruments absolutely envelop me on the M18i, and the crescendos are otherworldly. The depth of the sound and the rise and fall of instruments joining in and falling out are so much more noticeable and less nuanced. It also has better layering and separation, and more natural timbre and tonality. The Max has a warmer midrange and a slightly wider soundstage, but some "s" notes can sound a bit thin. The M18i has better bass resolution and sub-bass extension, but it can also sound a bit bright at higher frequencies, with more treble resolution and air. The Max is a great, simple dongle with a very nice and somewhat relaxing sound for the price. However, the M18i has far superior sound quality and more functions, including Bluetooth. Granted, it's over four times the cost, but the sound is just so good.

●KAEI TAP-2 (~$100) - The TAP-2 is an interesting device, offering the choice of using it with or without tubes. It can also function as a standalone amplifier, bypassing the DAC. It is quite large and bulky and is more transportable than portable. The M18i is small in comparison and has a sleeker, more expensive aesthetic. The TAP-2 has no screen, no app support, and no balanced input/output, but it does have an internal battery for use on the go. The TAP-2 does pick up some electronic noise and interference from the phone at times and has a high noise floor with quite a lot of ringing/buzzing. The M18i has a more natural timbre, better resolution, and a more dynamic presentation with a deeper soundstage, but the TAP-2 offers a little more warmth due to the tubes. The M18i has a bit more sub-bass emphasis, and its slightly V-shaped signature leads to more incisive treble notes. I do like the TAP-2's warmer and slightly darker sound, and the price and longer battery life are great. However, the M18i's sound quality is far better; it is much more portable, and the Bluetooth adds extra versatility, even if the battery life is poor.

Sound impressions:
Through my listening sessions and comparisons, I was able to draw conclusions about the M18i's overall sound signature. It has a somewhat V-shaped tuning that is engaging, exciting, and a bit in-your-face. It represents a marked improvement over each dongle I compared it to, granted it is also much more expensive. However, as I have stated many times in the past, the audiophile world is plagued by diminishing returns. There is almost always better quality to be found, but there will be a premium price to pay for it. While the M18i is better than the other dongles, in some cases the improvement is subtle and may only represent a 30% increase in sound quality. But hey, better is better, and my goal is to accurately and honestly convey what I hear, price be damned. The consistencies of the M18i that I noticed are the excellent bass articulation and texture, sub-bass extension with more rumble and reverberation, and an overall fuller-sounding low end. It also has a certain depth and maturity to the midrange, with both vocals and instruments sounding more natural and organic. The treble exhibits just a little more air and extension and comes across a bit brighter as well. The technicalities also improved, including the dynamics, timbre, separation, and layering. One area where the M18i could be vastly improved is soundstage width, as it can be quite narrow depending on the transducer.

In conclusion:
My initial impressions of the M18i were not all that favorable, but once I spent more time with it and understood its strengths, I started to enjoy it much more. So, who is the M18i for? I'd recommend it to anyone who wants a very dynamic and engaging DAC/amp with an exceptional ability to push any IEM to a more exciting presentation and get the best out of the bass response. It has great synergy with all BA sets like the Orchestra Lite, bringing out a better sub-bass presentation. It also paired well with the Softears Volume S. I reviewed this one recently and found that the low impedance mode lacked a bit of excitement, but the M18i helps bring it out. It might be the most engaging-sounding dongle I've heard to date, and when it hits just right, nothing can compare to the dynamics and depth of sound. While it definitely adds a lot to any transducer, it wouldn't be the first DAC/amp I would reach for when I'm in the mood for relaxing. So, who should pass on the M18i? Obviously, if you don't have $350 to spend on an accessory like this, you should look at the plethora of cheaper alternatives. Also, anyone wanting a more relaxed sound signature or one that offers a wide soundstage will probably not enjoy it. Based on sound quality alone, I can vehemently recommend the M18i. However, those needing a long-lasting battery for on-the-go use should look elsewhere. There are also virtually no extra functions such as app support, EQ, or digital filters. There are many great products on the market today, and the FiiO BTR17's existence might make you pause on purchasing the M18i. I haven't heard it myself, so I cannot comment on its sound quality, but it boasts a larger battery capacity, built-in EQ, app support, better stock accessories, and is $150 cheaper. I do not want to minimize the M18i's sound quality, because it really is fantastic. However, considering the price, poor battery life, and lack of features, the M18i unfortunately leaves much to be desired.