A Survey of Digital Audio Players Part 1 Calyx M


Calyx M
For most audiophiles, the first exposure to Korean firm Calyx came back in 2011 with their highly regarded "24/192 DAC". What most people (myself included) didn't know is the company actually started way back in 1999, as a fabless semiconductor company working on proprietary PWM and class D amplification. So Calyx has a lot more industry experience than many people know about.

Apparently not content with their several recent products in the traditional 2-channel space, Calyx decided to attack the personal audio segment by releasing a flagship DAP. Dubbed the Calyx M, this $999 device aims to compete with the top audiophile DAPs on the market, regardless of price. Does it succeed?

External Design
The Calyx M is a very straight forward design. When viewed head on it basically looks like a modern smartphone. Change angles and you'll spot the difference—at nearly 15mm, the depth is over twice that of an iPhone 6. Weight is substantial as well, a hefty 230 grams. To put that in perspective, an iPhone 6 is 129 grams, and the Sennheiser Momentum headphones are 190 grams. So the Calyx is in a whole different league compared to the diminutive Sansa or Sony models we've discussed so far.

I dig the feel of the M—it has a solid heft to it, with a substantial aluminum body and nicely laid out transport buttons on the side. The volume slider is unique in being magnetic rather than permanently connected. A gimmick? Maybe, but it feels smooth during use so I'm on board with it. Users can opt for software control if they prefer. Display is listed as 4.65 inches, virtually the same size as many phones including iPhone 6 and numerous Android models. Calyx went with a Samsung OLED model and I find it quite pleasing to the eye. Resolution is 1280 x 720 which is merely average when judged in smartphone terms, but perfectly adequate for this application. I do have a few gripes with the user interface but display quality certainly isn't one of them.

Internal Design
The M sports some nice audio hardware—ES9018-K2M Sabre DAC chip feeding a discrete class A output stage—based around a decent if not overwhelming platform featuring a Cortex A5 CPU (as found in the iPad 2). It can handle almost everything you could ask for in terms of playback, from "lowly" CD quality 16-bit/44.1kHz to the latest DSD128 and everything in between. Output impedance is right around 2 ohms so the M can handle low impedance, multi-BA driver IEMs without issue.

The main surprise here is the class A output stage which gets the device slightly warm to the touch during extended listening. Given the company's history in PWM amplification I would have assumed that would be a natural choice, putting the device somewhat in line with the Sony in that aspect. What we get instead is a fairly potent "traditional" amp which sounds excellent, but may be partially to blame for the mediocre battery life. More on that shortly.

User Interface
Like the competition from Astell&Kern, Calyx started with Android and skinned it so heavily as to be barely recognizable. There are a few hints, such as the pop up window second guessing your command to power down. But in general I'd say the average non-techie user might not make the connection. The first time I used the device it was rather underwhelming in terms of speed. Transitions were choppy and delays were frequent and frustrating. Unfortunately it felt like yet another botched UI attempt from a high-end DAP—perhaps more ambitious than most, yet not much more successful.

Fast forward to now (several firmware updates later) and things have really improved. The UI is generally smooth and stable, with just the slightest bit of choppiness once in while to remind us of the relatively modest CPU on board. While not being quite as intuitive as the AK240 or even the Sony A17, Calyx still does a good job overall. It's easy to navigate, with emphasis on swiping rather than button mashing (but only when it makes sense to do so). The M also makes good use of screen real-estate by showing thumbnails while scrolling through music.

One complaint I have is how it rescans the library after each reboot. This has been a complaint going back quite some time, and Calyx really should have taken care of it by now. A big strength of the M is the ability to accommodate large collections via its dual SD card slots plus generous internal memory. Encouraging massive libraries yet unnecessarily scanning after every boot seems rather counterintuitive.

Overall, the M user interface is still plenty satisfying. It trails just a bit behind that of the AK240, but not by much, and with some firmware tweaks I could see it catching up for the most part.

Calyx made a wise choice here by offering not one but two expansion slots—one for full sized SD cards, and one for microSD. There's also 64GB onboard storage to get you started. That's enough potential space for a fairly massive library. Some might question the choice of microSD—why not use two full size slots like some of the competition? True, microSD is more expensive, and max capacity tends to be smaller. If I only get once slot I'd prefer regular SD. But having both allows me to play any type of card someone might hand me, so I find the flexibility worth the trade off.

Another wise choice is the ability to run as USB DAC. This essentially turns the M into a desktop DAC/amp for stationary use. Using the XMOS chipset, drivers are required for Windows but not for OSX machines. Bonus points for charging via microUSB rather than a separate port.

Aside from that, things are rather limited—just a single unbalanced headphone jack. There's no dedicated line out, and no digital output either. Calyx seems to be making a statement that their integrated processing and amplification are of sufficient quality that we really don't need to add external devices. And I can't say I disagree.


So far I've been almost totally complimentary of the Calyx M—that ends now. The Calyx M has poor battery life. There's just no way around it. Initial claims from Calyx ranged from 7 hours to as high as 10 hours, which still isn't amazing by any stretch. Instead we end up getting a consistent 4 to 5 hours. No matter how good the device might be, that's low enough to knock it out of contention for a lot of users. To make matters worse, it doesn't seem to have any provision for auto power off. If you forget to power down when you stop listening, the player will be dead by the next time you go to use it. This again seems like a simple thing Calyx should have taken care of long ago.

Sound Quality
The Calyx M sounds excellent to my ears. It has a rich, bold presentation which brings to mind quality desktop gear. I hear a bit of warm character which helps it stand out from the competition. By way of sonic analogy—if the AK240 is a modern DAC with a focus on detail and clarity, the Calyx M is closer to the beefy Parasound DACs of old, with the Ultra Analog R2R DAC chips. It isn't a slow, syrupy sound in the least, yet I do hear a certain thickness of note absent from the AK240. I find this interesting since the M uses an ESS Sabre chip, and some folks tend to characterize the "Sabre sound" as being thin and strident. The M is anything but. Of course, it's difficult to know if the DAC portion or the amp portion is responsible for this character, but either way I quite enjoy it. Details are still plentiful but aren't paraded around as the main event. It's a non-fatiguing sound that I can enjoy for hours on end—assuming the battery doesn't give out on me.

The M is quite versatile as far as headphone pairing. It comfortably drives most cans without much trouble, save for the really difficult stuff. Obviously the HiFiMAN HE-6 is a no-go, and most other planar magnetic models don't seem to hit full stride either. This is not unexpected for a portable device. Dynamic cans work very well—bright headphones in particular get a helping hand from the smooth, creamy sound signature, resulting in a more palatable presentation. It may not be strictly accurate but damned if it isn't pleasing to the ear.

I don't want to overstate this minor coloration. By no means is this a rolled off, dull sounding DAP. It's not even necessarily "dark", but more like just a tad "relaxed" up top. Combined with the richness of the bass and that wonderfully full midrange, the overall effect is what some might call "analog" sounding. Interestingly, detail retrieval remains quite strong, with nuances and micro events still very much in evidence. Of all the DAPs here, this may be the one I most frequently gravitate towards based on sound quality alone.

I've spent considerable time with the original Calyx 24/192 DAC as well as their latest flagship, the $7k Calyx Femto. Both devices have their charm, and I was expecting the M to follow suite in terms of sonic signature. I was pleasantly surprised to hear Calyx do something a bit different with their portable device. The M shares certain sonic traits with the dedicated DACs yet has a warmer tonal balance which, to my ears, is more musical and enjoyable. If their next dedicated DAC goes in this same direction, I can easily see it finding a home in my system.

elfary's picture

BTW complete measurements for iPhone and some boutique daps can be found at:


Skilled guy with pro gear. Source measurements seldom get better than this (unless nwavguy comes back from hereafter).

It would be nice to give a shot to an iPhone 5s/6. Superb iem drivers in my book.

veggieboy2001's picture

...thank you John! Really well thought out and enjoyable.

If you can get your hands on one, I'd love it if you can try one of the LH Labs Geek Wave DAPs...They put a lot of work into them with their indiegogo campaign, I'd enjoy hearing your take.

some links if you haven't seen/heard of it:



John Grandberg's picture

I can't say I'm a fan of their marketing practices... the gear well end up being very nice, but the circus act surrounding it is another matter entirely.

I would be rather upset if I was a backer on some prior offering, still waiting for delivery, watching announcements for new models keep popping up.

I'm happy to evaluate a final product once it becomes available. Until then I see no point in discussing renderings or specs or prototypes.

veggieboy2001's picture

I'm much more interested in the end result...the "marketing practices" are nothing but smoke & mirrors...I can't say I (totaly) blame them for trying to get a "buzz", but I thought they were closer to a "final" production model. Thanks for the response, (and the reviews!)

elfary's picture


Even if we are nitpicking here... you can trust me: iPhone 6 is 2.3 and it is identical as that of iPhone 5s.

Ftr iPhone 6 Plus does not sound nor measure identical to iPhone 6.

In any case given the ubiquity and convience of iPhones it would be nice to read you opinion about how it does stack against competition.

A few weeks back a former musician blindtested a bunch of guys (Pono/iPhone 6) and great majority chose iPhone. Bottom line is do not understimate iPhone headphone outs just because they are too mainstream.

John Grandberg's picture

I find it difficult because Apple seems to change each time. I remember the iPhone 4 was around 1 ohm, the 4S was double that, the original iPhone 5 was well over 3 ohms... perhaps my mistake was thinking the 6 and 6+ were identical.

I do think iPhone/iPad sound quite good in general (which I mentioned in the article), and only a select few Android phones can match them.

echineko's picture

I've just been thinking of upgrading my current Sony NWZ ZX1, and was actually looking up most of the DAPs listed here. Looking forward for part 2 and your overall conclusion on these :)

elfary's picture

Android handsets have come a long way in the last few years but output power is usally on the dire zone(seldom it goes past 0.5 Volts with no load). Only HTC and Meizu seem to strive for more serious voltage.

Still UI glitches, interference and hiccups are a common place in the Android marketplace whereas Apple is pretty much a bugless experience audio wise (As long as its volt suffices to your earphones). And UI and ergonomy are beyond what words can convey.

ashutoshp's picture

Great review John as, always. I would love to hear your opinion on the sound quality of a DAP vs. that from a smartphone streaming digital audio via USB to a portable DAC/amp like oppo's HA-2 (eg, Lightning for iDevices and USB OTG for Android)? Recent updates to Android and Apple devices allow compatibility with a lot more external DAC/amps than ever before.
Despite the benefits, I can't seem to justify buying music anymore considering the streaming (TiDAL) options available. I come from a generation where we had no option but to buy music CDs, which was a 50:50 option, at best, so I ended up having so much junk in my collection that I fell on my knees when I first heard of streaming. I have little desire for a DAP and and I have even less patience for clunky user interfaces. I could be wrong but it seems the ones with the good interfaces are either extremely expensive (Sony and A&K) or lack 'juice' (I'm looking at you Sony).

bikermanlax's picture

I've come to the same conclusion as John on the use of an amp with the X5. I'm using a Alo MKIIB w/ great results. My "sorta porta" set up.

My go to recommendation for a newcomer is the Sansa Clip, you can't go wrong with that one.

Agree that the X3 (2nd gen) should be thrown into the next review.

BadEars's picture

With all of the hype around the Pono player, I was dissapointed that it didn't make it into the round up... If only as an A-B compare or post script.

John Grandberg's picture
Pono will be included in part 2. I didn't receive it soon enough to make it fit here but don't worry, its coming.
jk47's picture

thank you for this review. i look forward to the next installment. some other daps i'd love to see included are:

1. the dx90 - i understand your annoyance with ibasso for making you an unwilling beta tester for the dx50, but the dx90 is the dap i use along with a lot of other head-fi members. it is thus a useful reference for comparison for a lot of your readers.

2. i'd like to second the inclusion of the cayin n6. this dap has generated an enthusiastic thread at head-fi and members there are lauding it highly. its price is such that if it is really as good as its owners say, it would be an incredibly great value, price/performance piece of equipment.

3. the lotoo paw - almost as expensive as the ak240. of course there are diminishing returns with increases in price, but how does it compare with the ak240, and with daps a rung or two down - the new hifiman 901s, the calyx, the cayin? is there really much extra value in reaching up into the stratosphere to purchase a $2000-$2500 dap?

4. if it's out in time, the soundaware esther. similarly, if it's out in time, the geekwave.

in all these reviews, i'm really interested both in the absolute quality of the sound, but also in the price/performance of the sq. that's part of my interest in hoping you include the dx90 - think it's quite high on the price/performance measure.

lastly, whatever you include, i'd like to applaud you doing this kind of round up. most of us do not have the opportunity to audition equipment, and rely on the impressions of others to make a purchase as a leap of faith. people who've already spent their money on something have a tendency to praise it highly, justifying the money they've already spent. thus, these deliberately comparative reviews are especially helpful.

John Grandberg's picture

Thanks for the post! Let's see:

1) I'll consider it, still mad at them though.

2) I have the N6 here now, So far so good, it's pretty impressive.

3) I'll shoot them an email and see if I can get my hands on the PAW. It would have to be blindingly impressive to justify the price.

4) Doubtful, but we'll see.

jk47's picture

oh yeah, i forgot the acoustic research ar-m2. these things are coming so fast you could make it a whole career. ;-)

julian67's picture

The "Clip Zip" in the images is not a Clip Zip, it's a Clip Sport - different hardware and fairly horrible even by budget standards.

The "Fuse" should be called a Fuze, and I think that is a Fuze v2, not the original Fuze. It is obsolete. There was a newer model with different hardware (much better in fact), the Fuze + or Plus. That is also obsolete.

The AMS based players (Clip, Clip+, Clip Zip and Fuze v1 and v2) all play back with a pitch error. This is audible, though a lot of people won't notice. In any case I don't think I'm alone in thinking that playing music back at the wrong speed and pitch is something of a disqualification. Rockbox firmware fixes this on the Clip, Clip+,Clip Zip, Fuze v1 and v2. The Fuze+ doesn't have this error (as mentioned it's different hardware). The Clip Sport supposedly sounds bad enough that a pitch error is the least of its problems, though I haven't heard one myself.

John Grandberg's picture

Yep, I didn't explain my pics well enough and Tyll just took a stab at the labels when he posted this. Will have to get it fixed. That yellow one is indeed a Sport which, as I mention in the article, is not recommended at all.

The Fuze shown is definitely the original. I don't recommend the Fuze+ and made that clear in the write-up. I also did explain how Fuze is discontinued but easily found all over the place.

The pitch error has been overstated imho. Many DAPs have slight pitch errors, it's just a question of magnitude. The original Clip had an error of more than 1% which should have been somewhat obvious to certain listeners. On the Clip+ it was down to ~.25% which equates to playing 440Hz as 441Hz, or 90 beats per minute as 90.2 beats per minute. I seriously doubt most people could actually notice it. Rockbox fixes it altogether, and the Clip Zip never had it in the first place.

julian67's picture

You're right, the Clip Zip didn't have the pitch error.

see stuff.caudec.net/rmaa

However it's worth pointing out that the pitch error was not discovered by measurements. It was noticed by people listening and the measurements followed as part of the verification and diagnosis.

As well as being difficult to live with for anyone with ears silver, golden or better (ha ha) it is impossible to live with for anyone wanting to keep time to the playback.

Not playing the music back at correct speed/pitch is not a small failing or just an esoteric complaint. It's an audible error in an audio playback device! Core function much?

The Clip Sport and Fuze+ do have hardware that is different from the AMS Sansas but they do not share the same hardware with each other - totally different in fact. They probably should not be dismissed as though somehow comparable or similar.

The Fuze+ is excellent. For example it offers more dynamic range, lower noise, lower distortion, lower crosstalk than the AMS Sansas. It does actually sound very, very good too! A forum member at anythingbutipod did RMAA tests on the Fuze+ and several other players (including Clip+, iPod Classic with and without Line Out Dock, and others), loaded and unloaded, and the Fuze+ is very good performer objectively and in terms of pushing play and enjoying the music.

I have owned a Clip+, A Fuze v2 and currently have a Fuze+ (and a few other players as well) and imo the Fuze+ is the best sounding Sansa player so far (also has huge battery life between 25 and 30 something hours in Rockbox). The Sansa UI is pretty but horrible to use. Fortunately Rockbox transforms it into a highly usable device.

OK I'll stop picking now.

Nice article btw!

julian67's picture

sorry, the link to caudec is in wrong place - should be in para 5, it's the RMAA tests.

julian67's picture

..of the Sansa players the only one which *maybe* sounds better than my Galaxy Note II (GT-N7105) smartphone is the Fuze+.

The others all have too annoying a collection of hisses, squeaks, clicks and all the usual EMI noise. The Note 2 is dead black silent even with sensitive IEMs, measures well, has low output impedance, and sounds great.

I really doubt that any budget player these days can outperform a premium smartphone, whether that's an iPhone or a top flight Android device. Cheap smartphones have crummy sound but the good ones really are good.

I use mine on 4G and VPN to home and so I have my entire lossless collection (over 1600 albums which is over 500GB inc scanned artwork) available anywhere I have a connection. I can't do that with a Sansa.

John Grandberg's picture

My recollection of the pitch issue is that users first noticed it with the original Clip. That model was roughly 20 cents off, which should be audible for some or even most users if they listen carefully. The Clip+ and Fuze brought that error down to roughly 4 cents which is certainly bumping up against the threshold of audibility. People knew about it from the earlier and more egregious version - had it not been for the larger error on the first Clip, the later instances may well never have been discovered. As for timing, the Clip+ and friends have a speed difference of roughly 1.5 seconds for a 10 minute track, or .2 beats per minute. Short of using it for metronome duty, that's rather difficult to detect.

As you say, it's a non-issue when using Rockbox.

For the Fuze+, I tried it when it first came out, and found it shockingly bad. They took arguably the best scroll-wheel concept around and scrapped it in favor of a touch panel, because touch panels were becoming popular.... in smartphones. Never mind that their panel was completely unresponsive, and their menu actually a big step backwards compared to what came before. But hey, TOUCH PANEL!!!

The launch unit I tried was also a step down in SQ. I heard the same from many friends and forum dwellers at the time, and even some "civilian" tech review sites who don't normally concern themselves with such things. It was "mushy" sounding and had significant hiss with IEMs, where my other Sansa gear has none. My Clip+ abd Clip Zips don't have any of the clicks or other noise you mention so I can't account for that. Perhaps it varies from unit to unit.

No Rockbox port yet existed so I wrote the Fuze+ off as unusable and moved on. If a later Sansa FW update and/or Rockbox ended up improving the sound, I obviously missed it. Wouldn't surprise me as they had nowhere to go but up.

As for the smartphones, I totally agree the Note series is excellent, as are many other top models. But the "average" Android phone is still lacking. I've got about a dozen here (long story) and maybe 4 out of that lot sound great, the rest are all seriously flawed in one way or another. Talk about clicks and pops and EMI issues.... yep, I hear it on many of those phones.

julian67's picture

Yes, Rockbox on the Fuze+ is transformative. I'd suggest it makes revisiting product well worth while and quite an eye opener...or should that be an ear opener? You can now configure the sensitivity of the touchpad areas and make the damn thing behave like any sensible person might expect. Another benefit of the player over the AMS versions is that it has more processing power and RAM and so it does a much better job of running a database and the pictureflow plug-in.

All official Sansa firmwares for the Fuze+ are ess aich eye tee, don't waste a minute on them.

I know I'm not alone in experiencing an unwelcome assortment of unwanted noises on the AMS Sansas (and I've owned more than one!). It's even noted as a known problem on the Rockbox wiki. Some people never notice it, or else they have players which don't exhibit the fault. To my mind known inconsistent build or component quality is not a positive selling point but it seems that getting a good one inoculates one to this strange and curmudgeonly point of view. he he he.

John Grandberg's picture
You've convinced me, I'll hunt one down and give it a try. I see lots of refurbs available which doesn't inspire confidence about Sansa's QA process, but I suppose the same could be said for the large quantities of Apple refurbs too.... so maybe it doesn't mean much in the end.
purk's picture

Thanks for a great and very comprehensive review!

When you conduct a review on the Pono, please make sure to utilize its balanced output for optimum sound quality. I do like the Pono in SE but the balanced output is considerably better in all counts. Please also add the Sony NW-ZX2 to the list as well.

John Grandberg's picture

Have a balanced adapter that Tyll sent over, not sure the brand but it's very well built.

I am still patiently waiting on Sony's PR people for a ZX2.

julian67's picture

I bought my Fuze+ 8GB as a refurb for about £20. It was as new with no faults. The seller at the time was Sansa's official agent for refurbs and had many thousands available at low prices. I got the impression that lots of these returns must be due to the terrible UI/touchpad experience because this kind of hardware is intrinsically reliable and with no moving parts is pretty difficult to damage short of immersing it or attacking it.

Anyway I hope you like it! Try a recent rockbox daily as the last official release was in 2013 and lots of stuff changed a lot since then, especially on new and "unstable" ports.

John Grandberg's picture
They appear to go for around $50 for the 8GB model these days, so I'll snag one ASAP. Supposedly a 16GB model exists but I can't find one anywhere. Expandable memory makes these distinctions irrelevant anyway.
julian67's picture

The 16GB models were always expensive even as refurbs and as you say the microSD slot makes 8GB here or there irrelevant. Also the flash memory in Sansa players has very slow write speeds so paying a premium for even more of it would not get good value. A Class 10 microSDHC card is ideal in these. 128GB cards work fine if formatted from exFAT to FAT32 (you'll probably have to change the partition type as well). I found the Fuze+ with Rockbox easily copes with a 128GB card containing hundreds of flac albums, both in database and file browser usage.

Jayhawklaw's picture

Great article. I love comparisons. I wish all publications did them. Dare I ask, do you have a guesstimate as to when part two will be published? I'm in the market for a DAP that plays High Res files and no one close to where I live carries all three of the one's I'm considering, but you've reviewed two of the three already and I bet you'll include the other in part two. I bet you'll give me more and others to consider to boot. I don't know whether to thank you or curse you for that.

John Grandberg's picture
Best I can say is "soon" and apologize for being vague. The format is set, the explanations for each category are already explained so no need to rehash that. It's just a matter of getting the appropriate amount of listening in and then going from there. Some of the DAPs I've had for a while so I already have a handle on them, but others just barely arrived. So we'll see.