I bought this Amp/DAC combo as a replacement/upgrade for my now-departed Asus Xonar Essence STU. I checked it out online, read some reviews, most of which were in German and I had to translate. The specs looked great and the reviews praised it for the most part. Please bear in mind that is was used with the following headphones, in order of hours: Hifiman HE-400, Audeze LCD XC, Audio Technica ATH-A1000X, VE Monk and Apple earpods for laughs.
 
This was initially a Amazon review I wrote a year ago, then modified and uploaded it here because I didn't find the product on Head-fi.
 
Packaging

It was neatly packed, arrived one day late, but I guess that's just the local post office, so it can't be helped. I opened it up, it looked great, but one thing that surprised me was that there was no USB cable included with it. To be honest there wasn't anything else in there except for the power adapter. How do they expect you to actually use it without that cable? It's a bit like one of those batteries not included deal, but on a different scale. They could have thrown in at least one of the cables (Toslink, RCA, USB), but none of them was there. No matter, I went down to my local store and bought one for 5€, no biggy, but still rather mind-boggling. Seems like a bit of marketing flaw, to be honest because they could have at least mentioned that there wouldn't be one in the package.
 
Form Factor

It's a neat little piece, with a small footprint, a smooth front with two 6.3mm headphone jacks, one volume knob and a Input selection knob. The top and sides of the device have a gritty texture and the contrast between the front and sides feels quite nice to the touch. A down side to this, however, is the fact that the top can easily collect dust and fingerprints are visible on the front, but that's not really a problem since I tend to clean my equipment every day or every other day. It has four small rubber "feet" which are very smooth. I honestly wish all gear came with little feet like these, I feel that they are perfect for using on a desk.

After about a year of normal usage, the paint on the sides seems to have faded and I can see the original colour of the metal. Nothing that isn't fixed by a bit of acrylic, but it's somewhat unusual, since I cleaned it quite often without using any odd substances that would damage either the paint or metal.

It has a simple on/off button which, well, turns the device on or off, which does its thing, I don't really have anything to say about it. It also has a volume knob, which rotates smoothly, doesn't seem to come off and doesn't get noisy after being used a lot as others. It also has a 4-step input select knob, which switches between Coax, Optical, USB and analog. It works fine, but I find it a bit rigid and it doesn't snap into place as "cleanly" as I would want it to, but that's just nitpicking.
 
Drivers and support

After installing the newest driver from the website and updating the firmware, it behaved well except for one little issue. It can't really do 384k/32-bit in the Windows settings, which I found very odd and somewhat dishonest on their side. I understand that it is possible via WASAPI in certain players, but it doesn't really matter. Because honestly? In many cases it may be rather hard to tell the difference and the impact isn't immense for me.
 

One issue I have experienced was with the driver. Specifically in its inability to recover from a crash. If the driver crashes, it takes down every Windows service related to Audio with it and every Application which was using it at the respective moment. Also it does not recover from crashes without restarting the PC. Please note that this does not mean that the driver crashes often, but I've been working with software for years and I have a knack for breaking things. It actually never crashed for me with normal usage.

Just device changing, ASIO and WASAPI modifiers and other such things caused it to crash, so I contacted Oehlbach support and told them what issues I had encountered while using the product on Windows 8.1, as the initial driver and the first update were made for Windows 7. Five days later they contacted me, apologized for the inconvenience and asked me to download the new version that they had just uploaded to their site and to let them know if I experience any other issues. I didn't expect it to be fixed (working in QA is the cause for said skepticism), but it was! I was quite surprised by their swift response.

I am now using it on Windows 10 and I don't have any issues with it.

One additional driver-related aspect is that if you have a motherboard which powers up the USB later than the startup (or software that does this. Or simply restarting all of the USBs via scanning or some similar method), the device will appear as disconnected and it will require being powered off and on again.
 
Sound quality

Prior to this I have owned a Creative Sound Blaster Zx, a Creative Xtreme Music X-fi and a Asus Xonar Essence STU, with which I spent quite a while and it was an amazing little piece of technology. So the following comparisons will be against the STU. Also I did not set up any specific EQ and everything was flat.

I started it up and immediately played Aerosmith's "Dude (Looks like a lady)" and pumped up the volume to test the stereo, but also the noise. At high volume the quiet passages of songs have a bit of noise, not very noticeable (and you really shouldn't be listening to headphones this loud), but it was there. Minor, but present. The highs sounded good and crisp, but not overdone or too strict, but yet again, a bit distorted at high volume levels (These are songs I have heard countless times, so I have a near-perfect idea of what they sound like, so I am able to tell the subtle differences, but yet again, this is easily fixable via EQ).

Next up I played Michael Jackson's "Thriller" and it was revelation. So open, so wide. The spaciousness of it all was amazing. Everything had taken its place exactly the way it should have. Every sound was where it should have been and music was playing. Real music, the way it was meant to be played. The mids were nice and smooth, very well rounded, but not constricted in any way. All very natural sounding. That's when I realised that's what was special about the sound. It was natural, more so than most audio gear can provide, but I digress. I wasn't quite sold on the mids just yet, so I put on Led Zeppelin's "Going to California". Once again the soundstage, the spaciousness of it all. After that song, the best word that I could find which would easily and accurately describe the mids was "pleasant". They were not too rounded or smoothed up as many amps tend to do, it just sounded good. As a final test for the mids I threw "Night Prowler" - AC/DC at it and just as it did years ago, it sent shivers down my spine, once again. I could hear the smooth guitar, the slow vibrato on the ol' Gibson SG, Brian Johnson's rough voice and the constant "nagging" of the cymbals. It was just as I remembered it, except for little detail. The detail itself. I could hear roughly the same things I had heard before, but now all of the sound had a different, grittier texture and it sounded better. The STU did, indeed, offer detail, but not to such extent.

Next up comes the analysis of the Bass and I feel that it requires a bit of a disclaimer: I am not a basshead. I do not enjoy excessive bass in my music, nor do I push up the low EQ. I like bass in music, but within normal range.

I thought that a great song to test the bass would be "Another One Bites The Dust" - Queen. I liked it. It was very controlled, not too obvious or overdone. It sounded right and blended in nicely with the rest of the instruments as they were introduced one by one. Although a good song to start, it's quite linear and I know that alone won't convince you kiddies, as it didn't convince me, either, so I went on with Led Zeppelin's "Heartbreaker" and here I noticed something which I hadn't noticed before and I was shocked. The bass had a rough texture to it. One that I had never been able to discern before. I was gobsmacked and I just kept on listening like an idiot. I could literally here the strings vibrate on the bass. No, not the sound the pickups send to the amp, the actual low frequency vibration of the strings themselves. I could hear the the pick grinding against the rough texture of the strings steel coil. I felt like a complete idiot and with that little revelation I could certainly say that clarity within the bassline was there. No doubt about it. Of course, even after that, I couldn't just pronounce myself just yet, but I was also at a bit of a halt, not knowing what to play next. So I decided to contact a friend which is really into mixing. I know the way he records and he uses complex procedures to get the exact sound he desires. Now, I'm not really into Dubstep or any and all related genres, but I felt that it would be a good test. I asked for a specific track, one of his yet-to-be-released-remixes and he provided a .Wav file, which had a very complex line, with an amalgam of sounds blended into it and a pounding bass line. I'm glad I did, because suddenly I could hear the hard, pronounced bass, pounding away in my ears, the metallic door shutting, the broken glass into the background, the plastic pounding into the plastic bottles, all of these sounds which he had mixed into one song and I could easily discern them all. Once again - clarity and also a sense of comfort with the provided bass. It wasn't exaggerated, it wasn't too thin or lacking and it wasn't too pronounced, it just sounded nice and well-defined. Also the whole ensemble of sounds mixed together without ever sounding muddy or linear.

I have performed additional tests with low quality music formats, for example a 320kbps .MP3 of Aloe Blacc's "Wake me up" (The one without Avicii) and it wasn't unforgiving with it. I guess I could hear a bit of a dithering artifact, but it wasn't unbearable or obvious. If you just want to enjoy your music, it won't bother you. If you are, however, obsessed with analytic listening, very high volume levels (and possibly when using IEMs) you may find it a bit unnerving. I also took out an old recording of Joan Armatrading's "Sometimes I don't wanna' go home", a song which I haven't heard in ears. While it did lack a bit of detail, it still did manage to sound good, there was no clipping, no general distortion or noise. Next up was another .MP3, this time it was Buddy Guy - "What kind of woman", yet again it sounded good, but one thing I noticed is that it wasn't as open as I remember it.

I am very satisfied with the overall sound quality of the Oehlbach XXL DAC Ultra, especially considering its price and size. It's nice to see Audio going down from the ridiculous prices I've been seeing in the last few years.

After owning this for a while I can add a few things. The way to get the best quality out of it is to use it via USB and it provides for a cleaner, rounder sound, not being as sharp as the one you obtain via optical cable. However it appears to smooth out minor imperfections in the lower quality formats, but may provide for a small loss of detail in high res files. That may prove to be a problem for the overly-analytical types, but it still offers a very good sound.

Conclusion

So to recap, great sound quality, really good price-performance ratio, no USB/Toslink/RCA cable, minor driver issues which have been resolved in 5 days of notifying the Oehlbach support. All of these are my argument for a four-star review of a solid product.
 
Thanks for the read and let me know if you have any questions!

Hey guys!

I know this is hardly the first review of these to ever be posted and I'm pretty sure everyone has covered all of the bases by now, but I've decided to throw in my two cents as well.

Introduction:

This is my first review here, so please don't lynch me.

I've owned these for two years and they have a special place in my heart as that one gateway drug that led me, not only to planars, but also to the higher planes of audio... Or so I like to think. Things have changed in the past two years and if you are looking for a good value, open-back planar, this is still a decent choice, but you might want to just pick up the HE-400S, since it has many improvements over the original.

Build Quality:

Ok, so to get this understood right off the bat - the build quality is good. It is. High quality material was used, the headphones themselves are mostly metal, the headband itself is also metal with a leather exterior.

However the design is not great. So to re-iterate, we have high-quality components, which have not been put together in the most ingenious of ways.

While the headphone itself is very sturdy, it has its issues:
 

1. The metal support for the headband si connected to the metallic casing of the driver through a screw on each side of the driver's casing. Now, the problem with these screws is that they have an uncanny tendency to unscrew themselves, so you have to screw them back in, which is quite frustrating. You don't even need to move around too much for it to happen, but it does.

 

1. The cable connectors... Ah, the lovely, lovely Hifiman solution for cable connectors (thank God, they've changed these with the newer models). They're something similar to reverse coax connectors, but I'm not really sure what. Either way, as the metal headband support screws, these also unscrew all the time, which is very, very frustrating and very damaging to the cable, in the long run.
   
   This can easily damage the cable as you need to rotate it to screw it in. Sure, you can rotate it in the other sense to compensate for it, but most of the time you're not going to get roatate in the opposite direction exactly as much as it needs to be screwed in and that will cause tension in the cable, which, in time, will damage it. For example, my Canare 3m cable died after about one year of usage and I had to replace it with the Silver-coated OCC 3m cable from Head-Direct
    
2. Stock pads constrict the sound and are not very comfortable. I'm sure that many of you are quite familiar with the "pads change the sound" phenomenon and it's true. The stock pads seem to take out some of the depth of the sound, it's like there's a very, very thin layer of plastic between your ear and the headphone.
   
   Additionally I spoke about the comfort. I am somewhat biased towards velour pads, because I like them more, due to not having them stick to my ears after long listening session.
    
3. Another issue is the weight that so many planars have. The HE-400 weighs about 440g, that's a little more than Fostex's T20RP MK3, which weights 328g and the Oppo PM-2 which weighs 380g. Additionally, the Newer HE-400S only weighs 350g.
   
    
4. The headband is not self-adjustable. I know a lot of people don't have a problem with that, but I prefer those, because they usually adjust accordingly, so I don't end up moving them by mistake and then not having the proper fit on my head and wondering what's wrong for a while... I imagine not many people run into this problem, though.

 
 
Sound Quality:
 
Ok, now here's the most important of them all. The sound quality.

Setup: I'm currently using my desktop PC, using a Oehlbach XXL DAC Ultra connected via USB (32-bit, 192khz) into which I plug my HE-400 directly. I have also used them with a Creative Sound Blaster Zx and a Asus Xonar Essence STU, but I will just talk about how it sounds with the Oehlbach, because it is the most fresh in my mind.

I'm using Foobar2000 as my player and my files are mostly FLAC or WAV, but I've also thrown in the occasional mp3.

I listen to all types of music, so I decided that I'm going to "audition" them and present their capabilities using multiple genres. Some of the songs I used are:

Michael Jackson - Thriller
Aerosmith - Dude looks like a lady
Queen - Keep yourself alive
Disturbed - Indestructible
Jesse Cook - Mario takes a walk
Queen - Another one Bites the Dust
Nova Menco - Journey
Joe Satriani - Surfing with the Alien
Steve Vai - Earthquake Sky
George Benson - This Masquerade
Guns n' Roses - Nightrain
Diana Krall - Fly me to the moon
Lee Ritenour - Night Rhythms
Ola Gjeilo - Ubi Caritas
Funkadelic - Maggot Brain
Infected Mushroom - Heavyweight
Pink Floyd - Comfortably Numb
Christina Aguilera - Hurt
Frederic Chopin - Grand Valse Brilliante (Interpreted by Valentina Lisitsa)

The tracks which I found more relevant are in bold and I will provide an explanation of why I found them to be important to my listening impressions.

So, right as you start listening to these, you can hear the immense soundstage and detail retrieval, they are really great, especially if you come from a closed-back headphone. Which I did, I tried them right after work, where I use a AKG K66. Not much of a comparison, I know, but it makes the WOW factor all the more obvious.
 
Michael Jackson's Thriller is a big-time hit for me. I've always loved this song, ever since I was little, but hearing it on a pair of HE-400 is completely different than hearing it on... Say, my old NEI television set, on MTV. I love this song and I listen to it when I try out headphones because of the great imaging and spaciousness it provides. From the start, when the synth and bass come in, you can tell that everything has taken its rightful place, being set just where they're supposed to be, offering a beautiful, beautiful imaging. It's not just once I've found myself pausing after the howling of the wolves, wondering what my neighbor's dogs are doing and why they're going nuts... Then I just realize that it's my music.

Aerosmith's Dude looks like a lady I use due to it's intermittent stereo sequence at that start. I generally blast the volume really high and see if there is any noise coming in between the guitar segments, in the quiet passages. While I did hear some noise, I later found out that the matter lies with my Oehlbach, not with my HE-400.
 
Queen's Keep yourself alive is a great song to show off the nice, smooth mids and incredible detail retrieval of this headphone. As soon as the song starts, you hear the guitar. You hear the pick strumming the guitar strings. You hear the edge of the pick grinding against the edges of the thicker strings' exterior metallic wrapping. It's fantastic to hear this much detail and it is quite soothing.

Indestructible, by Disturbed is, by far, my favorite workout sound... But as you can imagine, I don't really go to the gym with my HE-400, I simply enjoy the song at home, sometimes and that truly isn't difficult to achieve, as the HE-400 brings a great bang and slam with its bass, as soon as the instruments kick in. You can feel their "raw power" and their energy right off the bat, but sometimes it gets a bit too harsh (more on that later).

Another one bites the dust, by queen, I find to be a great tool for listening to bass and sub-bass and boy, does this headphone shine here. The bass is nicely balanced and controlled, without being bloated or feeling artificial in any way. It has depth and it packs quite the punch. It's full and it's not the type of fatiguing bass I've seen with some very V-shaped response headphones. I truly enjoyed it, despite being more inclined to a more mid-centric orientation.
 
Earthquake Sky is on this list because you can easily hear the nice slam of the drums, which really puts the lower range of these headphones to value.

Nightrain is just on this list because it's my favorite song of all time and it proves that, even though I love Slash a lot as a guitarist, Izzy Strandlin was quite under-rated and its that specific underdog effect that makes the first solo of Nightrain my favorite guitar solo of all time... Also the highs sounded harsh and edgy. That was unfortunate, this is one of the few times in which the high quality version of the recording was a poorer experience to me than the low quality mp3.

Funkadelic's Maggot Brain is a song I got into when I was in high school, just learning guitar. This is also one of the first lengthy solos I have ever learned, so it's quite special to me. Half of it sounds as smooth as a summer lake at dawn, really showing how the mids are well-balanced within the whole sound, showing off a very detailed sound. As for the other half, the higher-end of it all, it sound abrasive, if felt like sandpaper was being rubbed somewhere close to my ears, at times.
 
Infected Mushroom's Heavyweight is good as it takes you through so many sound, building a complex imagery around you, showing you how well individualized this headphone makes everything, giving proper air between each instrument and having everything settle in just right.
 
Christina Aguilera's Hurt, now that's a song I really enjoy and its depth gives me goosebumps every time. It's about regret, it's about not saying what you were supposed to, what you wanted to, at the right time, it's about missing out on important things in life, like family and the loss of a loved one and also about the difficulty to move on after such a tragedy, it's about... Those damn high peaks that ruin everything. There are seriously some weird high spikes in the upper range of the spectrum which can be heard throughout the song. There is also some slight sibilance and just a general sense of unwanted edginess and this time the fault is not with my Oehlbach, nor was it with my Creative X-fi Xtreme Music, nor with the STU...
 
This, my friends, was the biggest flaw in sound quality I found with the HE-400. It can be partially resolved by equalizing the headphones somewhere between the 9-11k, but nobody really wants to do that. Nobody wants to spend a lot of money for a headphone in order to make it sound right. Of course, I'm not saying it sounds bad, but flaws like this can be quite bothersome, especially when they're so obvious in songs you really enjoy.
 
Additional Notes:

They're easier to drive than most planars, but I wouldn't recommend using them on your phone.
They're not portable and are not meant to be, they don't fold, they're not closed-back, they don't have a carrying case/pouch.
The HE-400 can be used as a small, mono speaker if you have a powerful enough amp.
Hifiman HE-400 are moddable, they can be modded in many different ways in order to tweak either sound or comfort. I have not tried any of these mods, all I have done is change the pads on mine and I'm happy with the result.
They come in a cardboard box, with a plastic support, but I don't care since I don't want to pay a premium for the packaging anyway.
 
Conclusion:
 
These are a beautiful way to into things, whether it is high fidelity audio, planar magnetic headphones or just another plane within the Nirvana of good music. Sure, they're a bit clunky, a bit uncomfortable, but they provide great value for the money. The sound quality is great, but it could be a bit better. They'll always provide a good experience, but most of the time they'll provide a great one.
 
Within the context they were released in, all those years ago, I would give them four stars, but now with the existence of the much better, many-times-over improved 400S, I give them  three stars. Mounting that up to an average of three and a half stars, which I think is fair.

Apologies if I forgot to mention anything (I'm writing this while at work, don't tell my boss!), I will update if I find it necessary and may return to post some pictures of the headphones.

Thanks for reading, let me know if you have any question (though I doubt it, at this point).