This dac/amp provides amazingly clear and balanced audio and a lot of inputs/features in a portable form factor. There were a couple of small problems though. It does not come with a carrying case of any sort, which is not great for this glossy finish and glass front. The only cables that have data capabilities are the short ones, the long one is power only. I can remedy this by using another long cable I have on hand, but it was disappointing there wasn't a long data cable included. I do not consider these worthy of deducting a star from this amazing dac/amp, but I would give it a 4.5/5 if I could. I use these with my HD600's and it has no issue powering them. The audio is noticeably better than my desktop dac/amp (though it is a budget one).

Stopped working

I fell in love with the Questyle M15i dongle-style DAC/amp and got the CMA18 hoping for an upgrade as well as the flexibility of Bluetooth. It worked marvelously with my Focal Utopia and Focal Stellia. However, I had a poor experience using it with more sensitive IEMs. I tried 3 different IEMs: the 64Audio U4s, 64Audio Volur, and Empire Ears Odin. The noise floor was terrible, and they all exhibited a background hum and clicking sound during quieter musical passages as well as when nothing is playing. Used with my conventional headphones, I had no problem driving both the Stellia and Utopia (Focal's flagship closed and open-backed headphones, respectively). There was no evidence of a noise floor problem with them; the sound was clean and neutral in nature and I was quite happy with that. Another issue I didn't like is that I needed to set the iPhone at a very high volume before I could use CMA18 (both conventional and IEMs). With the M15i, the output volume matches the iPhone levels fairly closely, so it's very simple to use. With the CMA18, I have to be cognizant of the high volume and remember to set it back to a lower volume whenever I'm finished with the amp. Bluetooth was easy to pair, but the placement of the "function" button makes it far to easy to hit accidentally, which switches the input. Reestablishing the Bluetooth connection is simple but it takes a moment, which is an irritation. Also, the use of circuit board LEDs visible through the glass window is a Questyle signature. It's quaint an inobtrusive on the M15i, but the CMA18 is far more complex and this interface is very awkward. At this price point and this level of complexity, they should have provided a more sophisticated display. I understand their commitment to their design language, but in this case it is way off base. If I were using this only with conventional headphones, I might have been fine keeping this as a nice portable, but I started playing with portable amps mainly to support IEMs. For that application, the noise floor is a showstopper I am going to return the CMA18. Note: tested using an iPhone 12 Pro running off battery (no AC line noise) and the provided Questyle usb-c to Lightning cable. The Odin was tested with it's stock 4.4mm balanced cable. The U4s and Volur were tested with an after market pure copper 4.4mm balanced cable. I used only the balanced output and didn't try the single-ended output of the CMA18.

I want to preface this whole review by saying that there is a noise floor with sensitive IEMs and that it can be completely alleviated by using an Ifi IEMatch in either 3.5mm or 4.4mm. I know purists hate that and like to complain, but it solves the issue completely and sounds flat out incredible with IEMs still. It is a non-issue for me and I personally couldn't care less about it. Even with the IEMatch it is easily the best I have ever heard some of my IEMs perform even when compared to $2000 DAPs and a $30k desktop source chain. There's some magic in this thing. The CMA18 is feature packed, compact, rock solid and is easily capable of being the only amp/DAC almost anyone on earth could ever need. It has a very powerful balanced headphone amp that is actually capable of driving Hifiman HE6se v2s to volume levels that are plenty loud and the CMA18 doesn't current starve like every single other portable option I've come across including the xDuoo XD05 Bal, Ifi Diablo, xCAN, Gryphon, and Nano iDSD Signature. If I had to find a single thing to complain about, it's that it doesn't come with a protective case and is kinda slippery. Questyle, $50 Android DAPs come with silicone cases, get it together. How can you call yourself a premium brand and leave out something like a case for a $900 piece of slippery glass sided audio gear intended to be portable and moved around and pocketed a lot? It has a rock solid Bluetooth connection with the best codecs like LDAC and AptX HD. Very clean USB input that allows simultaneous data transmission and charging (which you can enable by holding down the input select button for 4 seconds to enable in any input mode except Bluetooth, which holding the input select button in Bluetooth mode triggers the pairing function but if you enable the play and charge mode in any other mode and switch to Bluetooth, it will still charge. Not listed in the manual, but there was a firmware update at some point that introduced this function). OPTICAL IN!!! which is super rare in a portable but so nice for connecting to some devices and really is so nice to have when it doesn't take up any additional space and is just hidden inside the 3.5mm input, which is also a stereo unbalanced input. The 4.4mm balanced input I think is actually super cool for a lot of reasons like the ability to have a stereo mic input which I'm not sure I've seen in anything with a 4.4mm input yet, so cabling might be a little tricky to deal with but not impossible and custom cables can be had for probably around $35 and that would be a wicked option if someone were to want this for an all in one PC setup for streaming. I did test the 4.4mm input and it sounds fine, but I definitely think the USB, optical, and specifically high res Bluetooth codecs is a little better but I'm not sure if this is because maybe it's using the ADC to convert before putting it through to the headphone or what but it is a hair less capable. The ADC sounds really really capable in the 3.5mm in with a microphone, super clear and detailed with zero hiss and great dynamic range. Every input sounds fantastic overall, but I do think the digital inputs sound the best and though the USB I think is the best overall, it can still be audibly improved with a DDC and it really is a meaningful improvement and worth it to me because I already own a Holo Red and it just works in my desktop setup. The sound quality of the headphone outputs is what matters most though, right? Absolutely. And thankfully this thing is just pure endgame material for quite literally anyone. Bass is extremely well controlled with great punch/slam and gobs of texture. It really is phenomenally well done and I have absolutely no complaints whatsoever in the bass department, but it is easily outshined by the mids. Oh. My. God. The mids on this thing have left me completely dumbstruck several times. The midrange timbre is just flawless, it's extremely articulate and smooth all while having flat out incredible amounts of texture all while being very spacious and well separated while never sounding recessed or too forward and an absolutely absurd amount of clarity that I can't quite explain. It almost makes everything else I've heard sound like it almost has midrange glare which I've never really come across, though treble glare in source gear is fairly common. I'm hesitant to say this because I've had a lot of extremely high end source gear and I might just still be in a bit of a honeymoon phase with this thing, but this silly little portable DAC/amp might have the absolute best mids I've ever heard in my life regardless of price or configuration. It's just beyond words the way the CMA18 handles mids. Treble is very well detailed and well extended, plenty smooth without being slow and is never sibilant. Very well done treble and pretty hard to find any flaw in it, but very good treble like this is fairly common these days and for some reason just doesn't come off as all that impressive, though it really is, just not at the level that the mids perform relative to the competition. Staging is extremely pinpoint accurate with absolutely top tier separation and it might be something to do with the miracles happening in the mids, but the spatial queues on this thing are just jarringly realistic and are extremely apparent in video games where you can visually see where the sounds are coming from and know the sounds are accurately placed. Imaging is great and I suspect channel separation on this unit is pretty good going by ear. Overall the staging is punching way above the portable bracket in a way I've personally never heard and there are lots of several thousand dollar source gear pieces that can't pull off staging anywhere near this good. It's not an exaggerated stage and it's not small, it's just honest. I've had the CMA18 in my cart on 2 separate websites since the launch months and months ago hoping for a massive sale because the price is quite high, lets be honest here, and especially at the original MSRP of $900. The cheapest used one I had seen up until a week ago was $600 and last week I saw one on eBay and asked the guy a question and he sent me an offer of $475 and I was too late to accept and it sold for $500. Next day this popped up on Vine and I have never clicked request so fast in my life. Now that I have it and after telling myself the price is completely unjustifiable, I can't believe how wrong I was. Portables like the xDuoo XD05 Bal at around $450 are great, but is this twice as good? Absolutely 100000% firmly yes. It is twice as good and then some. It is drastically better than the Ifi Diablo that was priced at $1000 originally? Yes, it is miles ahead. This thing is competing with $3000 DAPs from a pure sound quality standpoint, pure and simple, it really is that good. It's straight up capable of replacing almost any sub $1000 amp/DAC stacks or combo units and it would have more features and better quality and it takes up almost no room. I was hoping this would be my endgame portable but had a hard time justifying the price because of how skeptical I was on the performance but it really is easily my endgame portable and thoroughly shattered all expectations I had. This thing has completely broken me. It's just so good I can't really put it into words. If I could give this thing 6/5 stars on Amazon, I would. It's the best product I've ever gotten from Amazon in my entire life.