Rapid Reaction: Calyx M

Everyone wants in on the DAP game these days, and the supply chain for lower power, high quality D/A conversion is easier than ever to tap into, and it seems like every hi-fi equipment manufacturer in China and Korea is releasing something within the next 18 months, setting high-end portable audio ablaze.

With so many different products releasing in quick succession, each one touting the “high resolution” moniker, it’s increasingly difficult to determine which one’s actually truly worth considering.

Enter the Calyx M.

The Calyx M is a solid, solid looking player.



Calyx is the public brand of a young but well-known Korean firm of D/A conversion devices, Digital & Analog (D&A). Having previously been a Samsung partner that devised novel PWM (Pulse-Width Modulation) designs (i.e. Class D), they went off into high-end audio with gusto, first with the Calyx 24/192, and then with the Calyx Femto.

The Femto made waves across audiophile circles, not only for its near-$7000 sticker price, but also for its prominent use of customized, RF-hardened, aerospace-grade oscillators — oscillators that ultimately served as the model’s namesake. Calyx proudly touted its DAC’s sub-picosecond jitter capabilities.

However, Calyx was always regarded as more of a home audio firm that made desktop DACs. It made a few forays into the lower end of things with the Calyx Kong and Coffee, but the company never really made any kind of headway with personal audio buffs.

Thus, when Calyx announced the Calyx M in mid-2013, portable audio lovers were both surprised and delighted by the company’s change of pace. To make things even more astonishing, Dr. Seung-Mok Yi, head of Calyx, boldly proclaimed that the M player would take after the firm’s flagship Femto model both in voicing and style.

Despite initially fearing Femto-esque pricing, portable audiophiles breathed a sigh of collective relief when the Calyx M was introduced at the sub-millennial mark***. People took it as a sign that D&A was directly gunning for iRiver and its upmarket Astell&Kern offshoot.

***Please note that the $999 retail price might not include dealer markups for international distribution.


Taking advantage of its past experience with ESSTech Sabre ICs (both the Calyx 24/192 and Femto utilized the flagship eight-channel ES9018S chip in single and dual configuration, respectively), Calyx harnessed the power of the newly-released two-channel ES9018-2M as the heart of the M‘s digital-to-analog conversion system. Utilizing an ESS chip allows Calyx to decode just about every format available, up to 32/384 in PCM and DSD64/128 rates as well.

While neither I nor anyone else has had the privilege of taking the Calyx M apart and examining its internals, judging from D&A‘s modus operandi, the digital and power rails should all be fed by low-impedance, precision linear regulators, and the clock oscillators, while not necessarily rated for femtosecond-level jitter, should be very good.

All this wizardly implementation adds up to superb measurements — better than 114 dB DNR, 0.0005% THD+N (with no load, and 0.0008% with a 32 Ω load, typical), and 130 dB of channel separation  — world class numbers by any interpretation of the standard.

Output voltage, at 1.25 Vrms, is a bit “low” compared to that of many so-called audiophile DAPs, but is actually ideal for low-impedance, high sensitivity IEMs and headphones.

Output impedance is also very IEM-friendly at close to zero ohms (though initial tests from Germany are indicating the OI is closer to 2 Ω, at least for export versions outside of Korea), ensuring great damping factor even with the wildly varying impedance swings of multi-BA IEMs.

Features & Ergonomics

Clad solidly in copper-coloured aluminium, the Calyx M is a formidable-looking device. Pictures and renders make it look small, but this is unquestionably a large device, replete with a smartphone-sized Gorilla Glass reinforced 4.65″ OLED 720p (316 ppi) touchscreen. The screen is fairly nice, with no visible pixelation to speak of and decent viewing angles, but since my experience with it was that of an in-store demo, I wasn’t able to take it outside and determine its overall brightness in real-world use.

At the top of the chassis are two memory card slots, one standard-sized SDXC slot, and one of the microSD TF card slot. Additionally, the player comes with 64 GB of internal memory.

In direct comparison to the Astell&Kern AK240, I found that the AK240 was actually easier to hold, because its angled edges form a natural contour for the fingers to wrap around the chassis. The M, on the other hand, feels like a smartphone, and a thick one at that.

Luckily, the aluminium finish of the casing is a matte textured finish that doesn’t feel slippery at all. However, it is more prone to picking up fingerprints and skin oils than the beautiful Duralumin finish of the AK240.

Sometimes, smaller is better. In the case of the AK240's ergonomics versus that of the Calyx M's, this mantra holds true. Sorry, Texans.
Sometimes, smaller is better. In the case of the AK240’s ergonomics versus those of the Calyx M‘s, this mantra holds true. Sorry, Texans.


The case becomes somewhat warm to the touch even before playback ever begins, suggestive of a heavily Class A-biased analog output stage. I would’ve guessed that, judging from D&A‘s pedigree, that they would’ve gone with a charge pump-fed Class D amplification stage to make it better for portable applications, but I’m not complaining.

Of course, using the Calyx M over the course of about 30 minutes gave me no measure over the battery life of the device (it is powered by a single 3100 mAh lithium ion battery), but audio forums have been abuzz with rumors that it gets poorer battery life than its stated 7-10 hours. If so, then this lack of and overstatement of battery life would be a strike against an otherwise nicely conceived player.

The other, more apparent detraction would be the laggggggy UI. While the experience wasn’t nearly as terrible as my brief encounter with the iBasso DX90, swipes and animations did not feel fluid, and hampered operation significantly. I had trouble switching between navigation pages, and scrolling just didn’t feel smooth. Thus, I was unmotivated to explore the depths of the custom-written M:USE UI, though the product website’s diagrams show them off pretty well:

Diagrams from: www.calyx.kr

My hope is that both the M‘s purported battery woes and UI fluidity issues will be solved in due time with subsequent firmware updates. Otherwise, user complaints will surely pile up in their customer service inbox.


I spent some time listening to a few familiar tracks, such as the ‘Lush Life‘ track out of Audiophile Jazz Prologue 3, from Kent Poon’s Hong Kong-based Design with Sound recording studios and Diana Krall’s The Look of Love album.

To me, the Calyx M reproduces quite a natural sound. Dead quiet in background noise (it is measured to have <2 uV of residual noise), the M is a veritable black hole of DAPs and easily matches the stark, sanguine personality of the AK240.

While I didn’t do a direct comparison between the Calyx M and the critically-acclaimed AK240,  I did compare it directly to the HiFiMAN HM-901 (with the IEM A03 card). The first thing I noticed was that the HM-901 possessed higher levels of noise, while the second thing was that it was considerably brighter and sharper in tonality, lending to a sense of crystal clarity, but also to a distracting lack of depth to the musical image. Thus, I preferred the more relaxed, slightly warmer sound presentation of the Calyx M.

One caveat, however, is that I felt the M didn’t necessarily possess the kind of “boundless” spatial presentation some players tend to give off. It’s a little more intimate, with most of the information fed to you in the central core of the stereo field.



I sense a lot of promise in the Calyx M — its sound quality is amongst the very best that I’ve heard in a DAP, in rarified air alongside the very expensive AK240.

In the short time that I spent with it, it didn’t have the most mature of firmware, for while it isn’t without useful features, is just not quick enough to ensure smooth operation. While the player certainly isn’t cheap, it’s priced in the middle of all the new audiophile-oriented DAPs at around $1k, and yet it manages to decode nearly every audio format, sampling rate and bit depth known to man. So while I didn’t get to spend much more than thirty minutes with the M, at the very least I know I want to spend much more time with it.

For more information on the Calyx M, please visit the product website (English/Korean):


About Mr. T

Mr. T is an in-ear fanatic by day, and writes SOAP notes by night. He pities the fool who actually has the patience to read through his stuff.
(Full Author Bio)

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Mr. T

Mr. T is an in-ear fanatic by day, and writes SOAP notes by night. He pities the fool who actually has the patience to read through his stuff.

3 thoughts on “Rapid Reaction: Calyx M”

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