Disclaimer: A big thank you to Just Audio for loaning me the 120Ds!
The uHA-120Ds is Just Audio's combined USB DAC and class AB headphone amplifier. It measures 23x52x85mm and is rated for up to 40 hours of continuous use on it's internal battery. That's very impressive for such a small and light device (130g). You might be surprised by the price (£320) based on looks alone, but just wait until you hear what it an do...
The 120Ds' DAC is capable of decoding up to 24bit 96Khz audio from all the main computer operating systems (Windows, Mac OS-X & Linux). The icing on the cake is that it also works with some Android devices* and Apple i-devices too (with the Camera Connection Kit), not just with it's amplifier but it's DAC as well and since it is battery powered it can do all this on the move. This compatibility make the 120Ds possibly the most versatile portable DAC and headphone amplifier I've ever used!
The audio quality of the 120Ds is indeed impressive, not just because of it's size, but also because of how long it can last on a battery. I'd usually expect this kind of sound quality to last maybe ten hours at best, but the 120Ds manages four times that easily. I have tried a couple of high-end portable DAPs recently (C4 & AK100), the 120Ds keeps up with their audio quality while utterly killing them in the battery life department.
The stand-out features in the 120Ds' audio quality department so far have been a very clean sound (even for very sensitive headphones) and it's surprisingly smooth as well. It keeps many treble happy headphones nicely under control, while not losing detail in those upper ranges and that's especially impressive for a portable machine. It keeps low frequencies tight and bold (detailed bass). Mid-ranges are really great too - feeling exciting, well detailed yet smooth - making for some sublime vocal presentations. Separation and soundstage are also improved.
The first headphones that I tested with the 120Ds were the Sennheiser Amperiors. These got a really appreciable boost from the DAC/amp, making the often overwhelming bass feel much better than out of a portable. It didn't diminish the amount of bass, but it did improve the boomy nature, rendering more detail. This made for a great portable rig, combined with my smartphone. It's very easy to carry around, even if you don't want to use the entire combo on the move.
The only thing I could wish for here would be a more elegant cable solution. Something with a micro USB connector on both ends (remember it has to be an OTG cable too). The USB OTG cable on top of the normal cable are a bit yuk, even if they are reasonably short. This does provide a nice side project to make the mini system a bit more special. Finding these cables is difficult, but not impossible. I recently found a company called 'Mimic Cables' who make these cables to order for a reasonable cost.
My other personal favourite headphones also sounded great driven by the 120Ds - the Denon AH-D7000. These headphones can sound rather boring running directly out of a portable, but the 120Ds made the most of their expansive soundstage and massive bass depth, again this is pretty impressive boast from a portable unit, especially one so small.
Volume wise the 102Ds is friendly to almost anything I could throw at it. It's extremely noise free on very sensitive headphones, even in-ears and the dial has plenty of sensitivity and turn at low volumes. With this sensitivity I expected there not to be much volume left for more demanding headphones, but the delivery doesn't seem to be as linear as many others. It seems to keep on delivering more volume. I'm sure the most demanding headphones might still struggle, but I did not have any issue with it. Even the Hifiman HE-500s were handled well and with some volume turn to spare too.
As I mentioned at the beginning of the article, the battery of the 120Ds is rated at an impressive 40 hours. I certainly had no reason to argue with that figure either, only needing to charge it twice during 100+ hours of testing. It also gives plenty of warning when the battery is getting low and it recharges in 2-3 hours. This means it rarely becomes an issue. Another impressive feature of the 120Ds is it's ability to switch the unit into USB power mode, stopping the battery from draining when plugged into a computer. On top of that you can manually control when the 120Ds is charging. This mean you can stop it from charging the battery while you're using the USB power for music listening - clever!
TECHNICAL STUFF
As I mentioned at the beginning of this article the 120Ds is compatible with almost everything that outputs digital audio through a USB cable. Usually the sticking point here is Apple because they usually require a licence fee to unlock their digital audio through their dock connectors. This can be circumvented by the camera connection kit (CCK) for some reason. I have heard of DACs being able to do this before but usually the issue there is that they require more power than the CCK provides. Being powered by it's own internal battery the 120Ds does not suffer from this issue. So that covers iPhones, iPods and iPads compatibility.
I haven't heard anything about Windows Phone or Blackberry USB audio support, so please write me a message if you know anything about this. I'm looking at Windows/Nokia for my next handset so I am especially curious about this. That only leaves Android...
* DAC compatibility with Android is a little complicated. There are a few that support the feature, but as I understand it Samsung now add their own support on top of this generic one, so their newer phones (Galaxy S3 and newer) have good USB audio support. Despite this fact there are many DACs that will not communicate with these phones unless they're used with a specific software player that's quite unfriendly for music organisation (USB Audio Recorder Pro). Luckily the 120Ds does not require this, it will send any audio - that supporting phones are playing - through the USB port when an OTG cable is connected to the phone and DAC.
BUILD / CONSTRUCTION
The 120Ds feels very solid, part of that is helped by it's tiny size, but it's backed up by nice materials. The plastic corners and volume dial are not the most slick looking, but they do a great job of protecting the unit's corners from knocks and drops. The volume dial also being plastic saves the internal mechanisms from a little rough handing, which might not look great, but it's a nice touch for a unit that's build to be taken on the road.
Shown here next to my Galaxy Note 2 to help illustrate the scale a little better. Now I know this is a pretty big phone, but even so you can see how small the 120Ds is. It's still quite a lot shorter than an iPhone 4. To help visualise the scale for you Apple people - the iPhone 5 just fits inside the height of the Note 2's screen
Don't be fooled by the plastic trim, basic design, or small size - the 120Ds is wolf in sheep's clothing and in more ways than one. It's source compatibility is second to none, it's audio quality is top notch and it lasts for ages on a charge. If you do find a device that doesn't connect to it's DAC (which generally isn't the 120Ds' fault) then you can still use the 120Ds purely as a headphone amplifier.
Another aspect of the 120Ds' design that's not overly elegant on the outside but is brilliantly well engineered is the volume dial. It's brilliant with both high and low sensitivity headphones, which is a rare thing. So it's not the worlds most sleek chassis, but like the plastic edges that serve to protect it, this machine is engineered primarily to perform. It's function over form and I respect the great effort that's gone into making it work as well as it does. I can't really think of anything negative that's worth mentioning about this little gem of a machine. Do I recommend the 120Ds? Oh hell yes!
EQUIPMENT USED
Desktop PC (Custom Build), Dell Vosto Laptop Dell Adamo Laptop, Ifi iUSB, Denon AH-D7000, Hifiman HE-500, SoundMAGIC HP200, Mr. Speakers Mad Dog, Sennheiser Amperior, Samsung Galaxy Note 2
