RME ADI-2 DAC/headphone amplifier review Page 2


My initial evaluation proved troublesome in that I had some issues getting the ADI-2 DAC running happily on a Windows machine. Every Linux-based device I tried worked without a hitch (including really-high-res PCM and DSD playback) in usual Linux plug and play fashion. For Windows, RME offers the same ASIO driver from their existing line of MADIface products. It installed and recognized the device right away, but I had noticeable dropouts during playback that could not be fixed by increasing the buffer size in the MADIface control panel. I also had issues with Roon recognizing the DAC's ability to natively play anything other than 88.2kHz sample rates. After a series of reboots, uninstalls, firmware updates, Roon updates, and Windows updates, combined with breaks in my listening to focus on other then-pending reviews, the device now functions perfectly. I can't be sure what the issue really was, nor what the fix may have been, but I have noticed other reports of similar behaviour across various forums. So take that with a heavy grain of salt as USB audio can be a randomly-fickle beast. 

Also note that just before boxing the DAC up for return to RME, I did one last test with a brand new laptop. This time Windows 10 recognized it immediately via the built-in UAC2 driver and everything was good to go. Hopefully all future users are met with similar results.

The Sound

With everything up and running, the ADI-2 DAC proved a highly capable performer. My initial listening involved driving a Sennheiser HD650 from the 1/4" headphone jack, which later branched out to HD800, Audeze LCD-3, HiFiMAN HE1000, and Focal Utopia. In all cases I noted a superb balance between detail and musicality. The ADI-2 DAC clearly digs deep, unearthing subtle nuances on everything from Opeth's Ghost Reveries to Midnight Love by Marvin Gaye. But it's not overly analytical or glaringly bright, which is something I've encountered from several competing products from the pro-audio segment. Brush work and cymbals are rendered in a particularly convincing manner, and I love the feeling of "projection" for both male and female vocals – there's a sense of energy and immediacy that makes the experience lifelike. The unique flavors of my favorite artists are well represented across the board: familiar figures like Alison Krauss and Freddie Mercury, but also Adam Turla – Murder By Death, Chhom Nimol – Dengue Fever and Arleigh Kincheloe – Sister Sparrow & The Dirty Birds, all beautifully presented with their distinctive sounds. 

Holding the little ADI-2 DAC in hand, you'd be forgiven for thinking it might not have sufficient grunt to muster a deep, authoritative tone. The RME is, quite literally, a lightweight. Surely it takes a beefy, confidence-inspiring power supply to really do the job... or does it?

Getting past audiophile stereotypes, I actually end up totally content with the capabilities showcased here. RME uses a 12V switcher of the "wall wart" variety, but thoroughly cleans up incoming power through several stages of progressively higher caliber linear regulators. The end result is a rich, deep tone with excellent low-end slam and clarity, capable of doing justice to low-frequencies across the board. I tried swapping in a very nice linear power supply (with a price tag higher than the DAC itself) and did not hear any differences whatsoever, which proves RME is on to something with their approach.

The overall sound signature here is one of neutral clarity, with exemplary detail retrieval but also enough tonal richness to avoid feeling analytical. Anyone previously let down by studio-oriented gear which presented as thin or sterile should be pleased with the sonic contrast on display.

Headphone Matching

RME drives full-size headphones through the so-called "extreme power" headphone amp accessed through the 1/4" output. This delivers 1.5 watts per channel into 32 ohm loads, which is suitable for driving most headphones to absurd levels with plenty of authority. I found it to work quite well with nearly every headphone I tried; low-impedance Grados, high-impedance Sennheisers and less sensitive planar magnetic designs from Audeze and MrSpeakers. The only trouble I encountered was the massively expensive HiFiMAN Susvara – an admittedly unlikely pairing – which sounded only halfway decent and really needed more juice to hit peak performance. I'm generally a quiet listener so volume wasn't really the issue for me, but I could see it being inadequate for others. My chief complaint was a lack of gusto with dynamic classical pieces, along with diminished treble refinement compared to the best I've heard from the HiFiMAN flagship. Again, this is a silly combination, but we can extrapolate this result to other low-sensitivity designs like the older HE-6 or new HE-6SE, plus the classic AKG K1000 and probably a few others I'm forgetting. Generally speaking though, the vast majority of full-size headphones are fair game. 

If I'm being picky though, I did hear a worthwhile improvement using a good dedicated headphone amp such as the Rupert Neve RNHP, to say nothing of my reference models from Pass Labs or Violectric. It took me a while to notice this as the integrated headphone amp initially seemed excellent in every way. Yet after extended listening I noted a sense of "flatness" to the presentation, not from a frequency response standpoint but rather in terms of soundstage and imaging. Everything seemed a bit 2-dimensional, missing out on the rich sense of layering I heard with dedicated amps in place. This didn't really matter when listening to general rock or pop material where there isn't much of that to be had in the first place. But classical and jazz and various high-quality recordings of all genres really benefited from the superior ambiance reproduced by the outboard amplification. This was also headphone dependent, with a Sennheiser HD800 feeling the difference far more than a Grado RS-1 which has a relatively flat presentation anyway. So, in the end, the 1/4" output has a lot to offer but doesn't quite unleash the full capabilities of the DAC section.


Thankfully the ADI-2 DAC has a dedicated in-ear monitor output (via the 1/8" jack) which fares better. IEMs are highly sensitive and often pick up hum or buzz that make them unsuitable for pairing with powerful desktop gear. Even if they do end up being quiet, too much gain can still ruin the listening experience. It's tough to dial in levels when things go from whisper quiet to LOUD with a mere touch of the volume knob. The ADI-2 DAC is essentially silent in this scenario. It delivers 40mW per channel which is plenty for driving any IEM you might throw at it, and the sub-one ohm output matches well with complex multi-driver designs. I tried custom models including the Ultimate Ears Reference Remastered, 64 Audio A18t, Empire Ears Zeus XR, and various universal designs from Shure, RHA, Westone, and Sennheiser. In every case I noted inky-black backgrounds and plenty of range for volume control. 

The "flat" feeling I noted from the more powerful 1/4" output was not an issue here. While IEMs give a different take on soundstage, the better designs still do an excellent job in their own way, particularly with image specificity. And the little RME DAC was a big performer in this area. I particularly enjoyed it with the A18t and Zeus XR which present as being almost shockingly open and spacious. These are some of the best (and most expensive) IEMs in the world and they felt right at home plugged directly into the ADI-2 DAC. 


Last but not least comes the unique EQ feature of the device. I know EQ is a contentious issue in some circles, but it seems to me a very useful feature when done right. Roon has superb adjustment options, and other playback software gives EQ options of varying quality. But what about the large number of people using dedicated music streamers/servers like the popular Aurender models? They don't have a native option for EQ, nor are they compatible with Roon. Ditto streamers from Cambridge Audio, Marantz, Sony, and others. And what about those dinosaurs out there still spinning the silver discs?

The ADI-2 DAC brings useful EQ capabilities to any device with a digital output. I found that while going too far could easily ruin things, a bit of tastefully applied EQ can really help dial in many headphones, taking the edge off Sennheiser's high-strung HD800 for example. Bring a bit more air out of the original Audeze LCD-2 without damaging that creamy rich midrange. Dial back the Grado bite just a touch. Once you get the hang of it, you might wonder how you lived without it. 


Despite not being a "pro" user in any sense of the word, I could absolutely see myself buying the ADI-2 DAC. It offers a very strong value, certainly competitive in its price class based simply on D/A conversion alone. Factor in the useful EQ, plus the headphone amp which I found a mixed bag for big headphones but exceptional with IEMs, and you've got a device which simply has no peers. I've packed it up and sent it back but I already find myself missing it. 

RME Audio AG
Am Pfanderling 60 D-85778 Haimhausen Germany
+49 (0) 8133 918170

Vic's picture

I agree the parametric equalizer is a godsend for HD800. I always had a love-hate relationship with that headphone since it first launched many years ago. Finally content with it using careful eq. Like you said, roon and jriver and others already have good eq, but I play from a CD transport so those don't apply to me.

Also as a D/A convertor the ADI-2 is really good. There might be something nicer out there but I'll never afford it and the difference probably isn't very big to justify it anyway.

audiobomber's picture

I realize this is a headphone site, but I would have liked to hear an opinion on the RME when used as a preamp. The RCA outputs are attractive to me, and uncommon in audiophile DAC's.

A comparison would have been useful too. The Benchmark DAC3 would be interesting, or a comparably priced audiophile DAC (Mytek, Schiit, Chord, etc.)

John Grandberg's picture

Sorry I was trying to keep things short and sweet. Plus, as you said, this is a headphone-oriented site, so I didn't focus a ton of energy on preamp mode.

Having said that, I did run it for a while driving my Adam Audio monitors directly. It did a very credible job - volume tracking is superb, and I didn't feel like it was missing any tonal weight at really low volumes (as happens often with many DAC/preamp devices). Unfortunately I never threw in a dedicated pre for comparisons, so I can't say what level it really plays at. In isolation though, very satisfying performance.

For comparisons, I like it better than the Mytek Brooklyn+, the original Chord Hugo, and anything from Benchmark. Haven't heard the Hugo 2 yet. The ADI-2 DAC seems more even handed, smoother, less analytical than any of those competitors - not overly smooth or warm or majorly colored in any way, but it seems to capture "neutral" in a way that agrees with my sensibilities, while the others all lean towards, well... lean. Ideal treble reproduction also seems difficult for those competitors to get right, whilst RME nails it imho.

Sorry if this isn't detailed enough but that's sums up my thoughts pretty well, hope it helps.

Pharmaboy's picture

Thanks for another excellent & comprehensive review. One of the hardest things is to describe the sound of DACs...differences are usually rather subtle. I particularly like that you described the known sound of the chip used here, as well as that of the resulting implementation in this product. Very helpful!

Shockdoc's picture

The real Gamechanger. Stellar sound quality- no own sound , transparent like cristal , deep space silence between the notes , dynamic without limits - from deepest bass to whisper of breathing artist. And that all makes this DAC great. Now You can add an excellent array of DSP features. . DREAM ! For this money its not true. But it plays in my audio room. Thanks Santa !!!! Jacek from Warsaw (Poland)