Questyle CMA Fifteen DAC/Amp

Questyle​

Questyle Audio Engineering, hailing from China, is renowned for their expertise in crafting DACs and headphone amplifiers. They're particularly known for their Current Mode Amplification (CMA) technology, touted to eliminate any metallic tones and believed to have an edge over competing technologies.

Underlining their commitment to innovation, Questyle has been recognized with over 20 international accolades since 2015, including the CES Innovation Award, iF Industrial Design Award, VGP Lifestyle Award, among others.

As they unveil their latest offering, the CMA 15, anticipation is high for a product of intricate design and quality. Time will tell if it meets the high standards set by its predecessors.

Introduction​

How did I come across the CMA15? Well, as the global pandemic hit, I found myself in search of an alternative to my trusty Bose QC35 headphones. I had always believed them to be among the finest headphones one could acquire. I was oblivious to the world of head-fi until then. As a result, I journeyed from one upgrade to another, diving deep into the world of audio, eventually narrowing down to the Abyss 1266 PHI TC, Hifiman Susvara, and Focal Utopia after exploring numerous headphones. For on-the-go tunes, I chose the Empire Ears Odin and Oriolus Traillii JP.

Now, to establish a robust foundation for my headphone system, my quest has shifted to the perfect DAC/AMP combo. In my opinion, headphones contribute to about 95% of the auditory experience, overshadowing the role of equipment, cables, or other accessories. While these components hold significance, my primary focus was to first pinpoint the ideal headphones and then source the additional elements to round off the setup. Catering to a broad range, from the delicate Odins to the robust Susvaras, isn't straightforward. I've experimented with several devices, including the JDS Labs Element II, RME ADI-2 DAC, Topping D90SE/A90 stack, Niimbus US4+, and Chord Hugo 2. Currently, my collection boasts the Shanling EM5, Felix Euforia MKII, and WA7 3rd generation. The CMA15 is also on my list of devices to delve into as I refine my DAC/AMP system.

My curiosity about the CMA15 had been piqued earlier, but it wasn't available locally. I could've made an online purchase, but the lack of reviews and information held me back. However, fate had its plans when Questyle announced a head-fi review tour. I promptly registered and, to my delight, was selected, making for a serendipitous turn of events.

So, here we are. I hope to offer valuable insights on the CMA15 and share my personal journey with the device.

​

Build Quality​

Let's dive into the fundamentals.

The CMA15 is a dual-purpose unit, seamlessly integrating a DAC with an amplifier. Size-wise, it stands larger than units like the Topping A90/D90 stack but is more compact than the Niimbus US4+. It can comfortably sit on a desktop, although it would occupy a noticeable footprint.

In terms of build quality, it doesn't disappoint. The switches operate smoothly, exuding a premium touch. Everything feels sturdy and well-assembled, with no signs of any loose or shaky components. While the surface finish is commendable, it's not top-of-the-line. Questyle might want to consider enhancing this aspect to align with the standards set by some of their competitors. The design leans more towards functionality, suggesting that it's a product shaped by engineers, where technological efficacy overshadowed aesthetics. If I were to choose purely based on aesthetics, I'd be inclined towards the Shanling EM5 for my desktop over the CMA15.

ES9038PRO​

One might assume that a multi-functional device would compromise on certain features. However, the DAC section of the CMA15 doesn’t cut any corners. It employs the ES9038PRO chip, which is ESS's most recent flagship offering designed for audiophile and professional studio applications. It's arguably among the top-tier chips available currently, especially for those pursuing the delta-sigma pathway.

Current Mode Amplification​

Discussing this topic is slightly out of my depth since I'm not technically versed as an engineer and don't possess a complete understanding of the intricate mechanics involved. Nevertheless, I'll lean on Questyle's own description for clarity:

"Central to Current Mode Amplification is the principle of using current, as opposed to voltage, for the amplification of audio signals. This contemporary method of audio amplification is distinctively superior to traditional audio amplifiers in performance. Considered the 'engine' of the audio system, Current Mode Amplification boasts an entirely discrete and sophisticated structure. This allows for an impeccable sound performance so authentic that it feels as if one is present in the original recording environment. With the utilization of Current Mode Amplification technology, even everyday headphones and speaker systems can deliver an elevated auditory experience."

Questyle holds the patent for this technology, and many of their products bear its initials (CMA). This serves as Questyle's hallmark and sets them apart from their competitors. I'm genuinely eager to discern its real-world audio rendition.

Connectivity​

I'll keep it concise on this front; for a detailed overview of the connectivity options, you can refer to the product's data sheet or its official website. The device comes packed with a comprehensive suite of connections: XLR and RCA outputs, RCA analog inputs, USB type-b and type-c, optical, and S/PDIF inputs. It also supports Bluetooth input with the LDAC codec, which is a handy feature, and it's compatible with Apple Music.

One feature I genuinely appreciate is the inclusion of the USB type-C input. It baffles me that many manufacturers are yet to adopt USB type-C, continuing to release products in 2022 with the dated micro-USB.

For headphones and IEMs, you're covered with all the standard outputs: XLR, 6.35mm, and 4.4mm. This should minimize the need for multiple adapters, which is always a bonus! .

Sound​

Alright, let's dive into the auditory experience and performance .

To set the stage, I'd like to provide some context on how I approach evaluating sound quality. As I've mentioned before, in my view, the headphones you wear significantly influence the sound experience, accounting for about 95% of it, rather than the equipment, cables, or other peripherals you might use. It's entirely valid if you see it differently. After all, audio appreciation is a shared hobby, and each of us has unique perspectives and priorities. That's simply my angle on it.

For consistent testing, I use a sound meter to match the volume across devices. I employ a 1KHZ sine wave, adjusting it to register at 80DB. Although I typically prefer a softer volume for casual listening, I notch it up slightly for testing purposes. This method doesn't translate as well with IEMs, so my observations tend to be more subjective in those cases.

Additionally, I've curated a set of brief audio loops featuring instruments like cymbals, beats, and hi-hats. This allows me to contrast their rendition across various devices. These concise loops facilitate retaining sound impressions as I switch between devices.

Broadly speaking, the CMA15 delivers an impeccably crisp, detailed, and transparent sound throughout the entire frequency spectrum. Nothing particularly jumps out or overpowers, which, to me, is ideal. The device essentially recedes into the background, enabling my headphones to take center stage.

With the Susvara, the inherent natural resonance and faithful reproduction of instruments are distinctly apparent. Meanwhile, the 1266 TC offers a wealth of details, showcasing its characteristic industrial resonance and pronounced bass. The CMA15 has ample power to effortlessly drive these headphones, leaving no aspect wanting. Engaging with the CMA15 using my headphones was an absolute pleasure.





For me, a device must pass the IEM test before it even enters my consideration for acquisition. I've encountered several devices across various price points that emitted a hiss when paired with my IEMs. To me, the absence of such hiss signifies quality performance and exemplary engineering.

The CMA15 impressively remains hiss-free with my IEMs, a feature I deeply value. Listening to the Traillii and Odin using the CMA15 was a pure joy. The Odin delivered an intricate level of detail, showcasing its outstanding bass texture, while the Traillii raced with speed reminiscent of a Formula 1 car, and its electrostatic treble sparkled just the way I prefer.

Conclusion​

Overall, the CMA15 left a strong positive impression on me. It's equipped with all the requisite inputs, notably a modern USB type-C port and Bluetooth with the LDAC codec. For headphone aficionados, it boasts all the expected outputs: XLR, 6.35mm, and 4.4mm. Its use of the latest ESS flagship chips is evident in the listening experience. The sound is finely detailed, possesses a stark contrast against a silent background, and feels authentic – just as one would hope. Notably, the device doesn't impose its own sonic character, letting the true nature of your headphones shine. Plus, it packs ample power.

My singular gripe lies in its aesthetics – the design feels somewhat dated, making it less appealing for placement alongside my more design-forward gadgets. However, this is a purely subjective observation, as aesthetic preferences vary widely, and this critique could apply to several other devices too (here's looking at you, Niimbus US4+). Beyond this minor point, in terms of both sound and connectivity, it delivers everything I'd anticipate from such a device, and I wholeheartedly endorse it .

Disclaimer: This review is part of a North America review tour afforded to me by the manufacturer in exchange for my honest opinion, there's no incentive for me to write a good or bad review here.

Then again, nobody really gives horrible reviews unless the product is truly unredeemable. I think readers should take that into account weighing the scores.

A little about me
I'm not an engineer, let alone an acoustic engineer, so I can't formulate all my thoughts in an objectively scientific manner. I'm trained in social science, more precisely behavior economics. I tend to see a lot of human fallacies, so I realize my impressions, along with others', may also be under the influence of such fallacies.

My experience with audio gears started with headphones, and I was wowed by an entry-level Audezes coming from outside of the audiophile world in the early 2010s. Then my faith and expectations in the hobby got destroyed by the piercing sound of HD800 hooked to a Chord mojo. Then long story short, over the years I have eventually ventured into the far end of headphones and found my equilibrium at the Utopia with the legendary Cavalli LAu and the beautiful Italian Aqua La Scala 2. With that, I then went into the upgrade spree with speakers as well, with my most recent prized precession being Hegel H590 + Dynaudio Contour 60s. Fast forward to now, life is slowly creeping in, to interfere with my love for audio gears, I had to let the speaker systems go. I'm finally settled in IEMs because they are the most "life (wife) - friendly" options.

About my gears
That brings me to my testing gears. For source, I use either the MacBook Pro 2018, a desktop PC, or Innuous Zen mk3 music sever running a Roon Core. The benchmark dac/amp I have my trusty iBasso DX300 with amp module 12. As for the intermediary between an amp and my ears, I'm only using IEMs for this review. They are UM Mason Fusang, Final a8000, Leisurely Audio e16. To offer some perspectives for those who haven't heard these IEMs yet, I will try to rank them in a few areas of characteristics:
Overall cohesiveness and completeness: UM>Final>e16;
Details: e16>UM>Final;
Bass: e16>UM>Final;
Mid: UM>Final>e16;
Treble: UM>e16>Final;
I overall tend to reach for the UM buds more. Because they just sound correct and engaging in almost every song.

Build Quality

I think most will agree with me that the CMA15 is an extraordinarily well-made piece of gear. It feels smooth to touch, the weight is substantial for the size. The knobs and dial all scream quality. Some people knock the score down a bit because of the screws, but I feel they actually compliment the overall build with an authentic retro look. The size is perfect for a desktop system due to its shallow depth and thinness. The warm yellow indicator lights illuminate with the right amount of brightness. This is all I have to say about the build, it's awesome.





Sound Quality

I find everything to sound right with my small collection of IEMs. It sounds very similar to my iBasso in almost every way, and I'm not sure how I feel about this.
I had very high hope coming in, thinking a desktop solution will hand down have a leg up in every aspect, if not at least in a few areas. That didn't turn out. But on the other hand, I truly love my Ibasso dx300, it's a capable machine that never failed me, and probably considered one of the best DAPs out there. But with my prior desktop and speakers experience, I just have this belief (justified or not), that a similarly priced desktop Dac must be better than a DAP. I was a little baffled they were performing similarly sonic-wise. Most strangely, they even sound pretty much the same. I think I'd struggle to tell them apart in a blind test. You would think it's more strange when you realize they have very different DAC chip implementations - iBasso has 4 Cirrus Logic chips, and the CMA 15 has an ESS 9038 chip. iBasso is powered by a battery, and CMA15 is by a wall socket.

This all put me in a special reviewer limbo when I can barely tell my baseline and treatment apart. Especially that the audiophile terms are useless all by themselves. But, it's a responsible thing that I at least try to the best of my ability in describing how I experienced it. CMA 15 like the DX300, has an airy treble, albeit not what I'd describe as sweet nor seducing, it's just accurate. It has no obvious flaw, and doesn't bring any extra attention to peaky trebles. It feels as if the DAC/amp is taking a back seat to let the music and earphones express themselves fully without adding artifacts. Mid-range is quite nice with a full body to it that will bring any music to life. Again, no bloat, no additives, just neutral with a slight hint of warmness. Think of it as if the CMA is a neutral-sounding and neutral-looking orchestral hall with a warm AC turned on during a cool autumn evening, just letting the bands be the center of the performance. Bass is nice and without any noticeable flaw, but it's not the deepest I've heard. So, I guess that's something to improve on in the future. I hear no difference in soundstage between iBasso and CMA15. I have to note that headphones experience on these might be different from my IEM experience. I can't compare, because my Utopia had a broken driver recently.



Function
It's my conclusion that the defining hallmark of Chi-Fi is becoming the anti-fragility of functions. Try anything you can think of on it, and use it however you want. It will likely work because features they can add at a reasonable cost, the companies will do it for you without making a fuss about it. For example, my setup isn't a well-treaded pass making 100% emphasis on IEMs, but it worked as intended - no noise floor issue, drivers are not blown, and my eardrums still exist in their perfect state of happiness.

I also have to add the less talked about feature of low latency, latency is non-existent in my setup connecting any source I have. Gaming, movie, conferences on these are perfect. So once again, this is another life-friendly detail that shouldn't get overlooked even if Questyle doesn't advertise it. It probably owns this quality to the newest and the greatest XMOS X216 USB module they put in there. For comparison, my iBasso has a noticeable one-and-a-half-second gap.



Conclusion:
You should seriously consider this if you want to holistically improve life quality while maintaining Hi-Fi integrity.
If you're like me, want to upgrade from a DAP to a desktop solution, prepare to be shocked at how good the DAPS already are these days.

I possess the little brother Questyle CMA 400i for many years now and still a big advocate of this all-in-one unit, so I was eager to see what the current top-linne model can offer. I was always close to buying the Questyle CMA Twelve Master but was so pleased with the CMA 400i that it didn't happen.

As part of the European review tour I received the marvelous Questyle CMA Fifteen to try out for myself.

So I brought ALL my current headphones to the table to be tested with the Questyle CMA Fifteen over many days ...


Headphones that are very good on CMA15: Meze Empyrean (Burson 3XP Combo im PowerAmp mode might have a slight edge here)
Headphones that are excellent on CMA15: Denon AH-D9200, Kennerton Rögnir Dynamic, Kennerton Rögnir, Hifiman HE6SE v2
Headphones that really wowed me on CMA15: Klipsch HP-3, EM-U Teak, Dan Clark Audio Aeon 2 Closed, Focal Celestee, V-Moda Crossfade M-100

• overall neutral tuning with great snappy bass and authority
• brings out the individual sound character of each headphone in the best possible manner
• single-ended output equally good as XLR/4.4 balanced (verified with Hart Audio Cable interconnect switch)
• satisfying double relay click when turned on (singe relay click when switching source to analog input)
• finally the return of the analog input (even its single-ended)
• educated version of the Questyle CMA 400i

"chains" used for comparison:

• Gustard X26pro + Headamp GS-X mini
• Burson Soloist 3XP + Composer 3XP
• Singxer SA-1 + Denafrips Ares II
• Chord Hugo TT2
• Questyle CMA 400i
• Questyle CMA15 + Ares II (RCA)

The Questyle CMA Fifteen really gets the most out of your headphones without trying to change their individual character and adds a pleasing balanced bass authority.
Can also drive powerhungry headphones like the Hifiman HE6SE v2 without a sweat to their full potential even the nominal power output might not indicate that - there comes Questyles superior amplification ciruit into play!

Especially non-top-of-the-line headphones (like Klipsch HP-3, EM-U Teak, Dan Clark Audio Aeon 2 Closed, Focal Celestee, V-Moda Crossfade M-100) really shined on the CMA15.

Might not dethrone the Gustard X26pro + Headamp GS-X mini combo for me (yet), but if you look for true-to-the-source all-in-one unit with nimble bass presence and authority don't look any further - the Questyle CMA Fifteen is right for you!

... and if you would want me to choose between the Chord TT2 and the CMA15, I would go with the Questyle! I am really convinced that I need one myself too sooner or later

Update #01: I sold my Chord TT2 and did order my own Questyle CMA Fifteen after the review was posted and the review unit passed to next reviewer

So I was able to test drive the new Questyle CMA Fifteen DAC/AMP.




CMA12 / CMA15

Let's first talk about the device, as far as I could determine, the form factor is exactly the same as the CMA Twelve. Note that I am not referring to the "Master" version because I could not find the Master specifications on the Questyle site.

Over the years I have become used to brilliantly and beautifully constructed pieces (such as Musical Fidelity’s Trivista 300, the Cayin 500 as well as some Cairn mono blocks…) it immediately became apparent that the quality of construction is of the highest level. I was impressed by the somewhat artisanal type of build, a very thick aluminum front, a cover that oozes the same quality, everything is impeccably put together. Even the bottom where the round aluminum feet are mounted with an integrated O-ring shows as being from a very high quality, down to the smallest detail. Even the screws are black whereas on the CAM Twelve they were metal, in short I would descrive the overall quality as superb.

As far as its outputs are concerned, the CAM Fifteen has all the current connectors to connect your headphones, the universal single-ended 6.35mm jack, as well as 4.4mm Pentaconn connector and an XLR4 connector for balanced headphones.

If the quality/manufacturing/price ratio already was really nice for the CMA Twelve, I can only say that this has improved even more for the CAM Fifteen. I was really curious to listen to this new model with a more recent DAC, especially since this denotes a shift away from the Twelve’s original AKM 4490 DAC to ESS. As we all know about the AKM factory fire in 2020, an event that has disrupted the audio industry and forced many manufacturers to find alternatives, all while trying to safeguard (part of) their house sound.

I listened to this CMA Fifteen with different songs, some that I don't necessarily listen to anymore but that I've heard so much on different gear that I know them well as well as others that I consider to be well recorded. Listening was done from Audirvana Studio that reads form a library stored on my NAS. Most music was ripped from my CDs and where possible SACDs. Aside from that, I also connected the Fifteen to a MacBook on which I have Apple Music installed. So I alternated betweeb the CMA Twelve and Fifteen with a Wireworld Starlight 8 USB cable

• Maxime Le Forestier / Rather guitar / Ambalaba

On the CMA Fifteen, when playing with the Meze Empyrean, there is a lot of room and width in the soundstage, there is space between the different guitars. It does lack a little support and extension in the treble of the guitars on the left side, but the energy of the audience is great, full of beautiful sounds of clapping hands, and no distortion.

Switching to the Focal Utopia, immediately there is additional details, background details …. Everything is there but it's also clearer. Indeed although Maxime's voice seems pinched at the exit of the Empyrean, that’s also typical of the Utopia (it seems that there is an expensive cable that corrects all that…) . But it's a different presentation and we "get used to it". Switching back to the Empyrean also shows a "blown up" rendition. The Meze Empyrean definitely is the better match with the Fifteen. It's beautiful to hear the resonance of the rooms, although the width is a fraction less than on the Empyrean. Of course, with Focal Utopias, listening becomes a little more technical.

Going back to the CMA Twelve, the mid/treble is a little less refined, the applause is a little thinner, on the other hand the percussion on the piece "the man with the bouquet of flowers" seems more pronounced to me, it comes with good slam.

I don't have any other cable with my Focal Utopia to test (DM audio) but with the Empyrean I cannot stand the silver Meze cable, on the Twelve, the rendering is a little harder than on the CMA Fifteen.

• Eric Clapton / Unplugged / Laila

The different voices are well differentiated, especially the female vocals. With the guitars, the treble is gliding a little, I would like a little more support there. They come with good quality of timbre and detail though. I therefore reach for the Utopia to control the treble, it is better but could do better for me. The fact remains also there that the Fifteen offers a slightly better balanced overall sound where the CMA Twelve is a little less balanced and controlled.

• Lindi Ortega / Faded Gloryville / Ashes

On the Fifteen voices are superbly rendered, a very rich sounds, I play 2-3 guitar sustain tracks that are equally well rendered

• Madonna / Celebration / La Isla Bonita

The details in the beginning of the track are well defined, we clearly perceive the voice in the background. Switching to the CMA Twelve I did not notice a big difference on the percussion, and possibly as a result of this, impact of the bass also seems to be slightly reduced.

Kid Francescoli / Play Me Again / Moon

The synthetic sheets take off, some sounds seem to turn around the head, I definitely prefer this type of song on the Empyrean

• SPOHR: Music For Violin and Harp. Flight 1

Really nice airy representation, each instrument clearly defined on its respective side, it's relaxing but again for me if the violin creaked a bit more it wouldn't bother me. With this kind of music the Focal Utopia really takes off, its precision, its rigorous side work wonders, the notes really shine. It's superb and this makes clear that the CMA Twelve sound a little harsher.

Hop a Shot by Norah Jones/New York City

It sounds good, I "rediscover" this piece a little. At times the voice is doubled sometimes in unison sometimes slightly offbeat magnificent, it is superbly rendered and very important, no sibilance.

And a completely unknown album!! Come Away With Me

With “Shoot the Moon”” the CMA 15 reads 88.2/96. There is no time to relax here, both headphones are being driven at perfection. Both the Focal Utopia and the Empyrean come out with perfection, there is no lack of anything in here.

I play a bit of rock and other oases / acdc / Metallica / Cure / Ben Harper (superb on Live From Mars).

In short, the CMA Fifteen is a very nice and good device, it is powerful enough even for many harder to drive headphones. If the CMA Twelve was already very good with the Utopia, the Fifteen is even better I think, especially for the mid/treble part. The amp allows you to appreciate the results of each headphone. The pairing with the Empyrean is also very good, where the Fifteen’s slightly softer rendering allows me to use the silver meze upgrade cable. This allows me to gain detail and precision.

A little word with the Denon ADH 9200 which sincerely does not have to be ashamed in front of the two more expensive headphones. The Denon is rich, detailed to such an extent that at certain times I got so carried away by the music that I briefly wondered if it was the Denon or the Focal that I had on my head. For a closed back, it is amazing how open they seem. These are magnificent headphones that pair extremely well with the Fifteen. It combines the qualities, the detail, the bass. The only thing is that you might have to calm it down a bit with a copper cable. This is where I keep repeating myself because here the slightly softer side of the CMA Fifteen makes a big difference in the end, I can keep the Denon for a good while without getting tired. The Denon 9200 and the Questyle CMA Fifteen are an astonishing pairing!!!

So finally .. should one get rid of a CMA Twelve in favor of the new CMA Fifteen? In my eyes that is not a clear decision. Even if I recognize an undeniable gain on many aspects, where even the bass in the end may be cleaner on the Fifteen, its character also is a little bit less demonstrative, less punchy.

In the end it has left me in doubt .. because with this CMA Fifteen I find a certain balance and warmer sound that I like a little, the same balance and sound that made me prefer the rendering of my Hiby R6 to my Fiio m15! Indeed .. does this turn me into more of an ESS Sabre lover?"

First off, I'd like to thank Questyle for giving us HF'ers an opportunity to try out their latest amp/dac offering, the CMA 15 pictured above. They did not pay me nor provided any input for this review. All thoughts about this unit are mine alone.

So, let's start things off with what's included in the package. Out of the shipping box, the CMA 15 is enclosed in a rather spartan white cardboard box. A 5ft power cable, a remote, instructions, and other paperwork were included as well. I was surprised that two AAA batteries for the remote were missing from the package. Not a big deal since I already had some readily available, but one would expect some to be included here nonetheless.

The casing for the unit is metal, which is finished in a way that makes it somewhat of a fingerprint magnet (see photo above). I couldn't help but contribute a few additional fingerprints of my own to those that were already there when I took the unit out of its box. The volume control is motorized, which means that it displays more travel resistance than the cheap volume pots used in the THX AAA 789. Thankfully, the travel resistance of the CMA 15 is just smidge higher than the Alps Blue pot found in my passive preamp. In other words, the CMA 15's volume pot feels fine, it is smooth (not stepped), and motorized too. I mostly controlled the volume via the included the remote. Of course, any fine volume adjustments needed to made by hand.

Amps that I evaluated here:
Musicbee (FLAC) > SPDIF optical > CMA 15 (bias control set to High) > LCD-3, HEKv1, or HE-6
Musicbee (FLAC) > SPDIF optical > CMA 15 (DAC mode / fixed) > THX AAA 789 > LCD-3 or HE-6
Musicbee (FLAC) > Bifrost 2 (unison USB) > passive preamp > Bryston 3BST > HE-6

I also tested feeding the analog signal from my Bifrost 2 into the CMA 15 via the latter's SE input, a first for Questyle from what I gathered. This testing was short-lived because the sound from the Bifrost 2 sounded a bit grainy when fed into the CMA 15, something that I didn't perceive when feeding my Darkvoice with the Bifrost 2's SE output using the same cable. My initial impression is that the SE input of the CMA 15 is second class to the CMA 15's digital inputs. I feel that Questyle, again, designed the CMA 15 to be used as an amp/dac combo, which I don't mind since the CMA 15 amp/dac sounds pretty good. I will be interested in reading impressions from subsequent reviewers of this tour regarding this feature.

I didn't test the CMA 15's bluetooth feature nor its MQA or DSD decoding capabilities. Also, I didn't test the CMA 15 with any IEMs. There are gain switches underneath the unit for iems and headphones. I'm sure that people would appreciate if such switches are presented in the front or in the rear of the amp. It is quite inconvenient to lift the CMA 15 up and toggle the gain switches when switching from iems to headphones (and vice versa). To me, I do not really care too much since I'm mostly a headphone user.

As for the sound of the CMA 15, I describe as being neutral with a slightly bright tilt (edit: I'm coming from a BF2 + Liquid Platinum | LAuX, so a warmer setup). I will compare it to the THX AAA 789 since I believe a lot of people here are familiar with the character of the 789 and amps of its ilk. Bass impact (i.e. slam) is noticeably strong with the CMA 15, considerably more so than the 789. The 789's slam sounded dull and mushy compared to the CMA 15. This difference is most apparent on the opening bars of "Protection" from Massive Attack on my LCD-3's. Also, the 789 sounded more closed-in, congested, which meant that imaging was far better with the CMA 15. To my ears, the 789 has a nasty habit of overly sharpening the edges of notes, which makes it sound a bit cold and unnatural. Thankfully, notes on the CMA 15 sounded a bit more rounded and fuller, and thus more natural, in my experience. Overall, the CMA 15 presents a clean and spacious sound with wonderful macrodynamics.

I really enjoyed listening to my LCD-3 and HEKv1 through the CMA 15. The HEKv1 is known for its soft character and the CMA 15 provides it some of the macrodynamics that it lacks on most other amplifiers (power amps help alleviate this issue with the HEKv1 but that's a whole 'nother kettle of fish). However, the CMA 15 came second best to the 3BST when it came to driving my HE-6 (modded 4-screw). To my ears, it was interesting that the 789 performance was not far from the CMA 15's when it came to driving this monster can. The increased bass impact from the CMA 15 with the LCD-3 and HEKv1 was a bit more muted when driving the HE-6. I noticed the size of the image increasing when going from the 789 to the CMA 15 and then to the 3BST. The slight bright tilt from the CMA 15 came to the fore with the HE-6's, whereas the 3BST+BF2 combo exhibited better control and sounded far more spacious than the other two amps. This spaciousness might reflect the character from the BF2, which I noticed exhibited more soundstage depth than the CMA 15's ESS DAC when switching back and forth between the two sources using the CMA 15's remote during my brief testing of the BF2 with the CMA 15 (see above).

Overall, I think the CMA 15 is a nice all-in-one unit that synergizes well with planar cans and offers a lot of convenient features.