RME ADI-2 DAC/headphone amplifier review

I've always found the divide between the "Audiophile" and "Pro Audio" scenes  fascinating. While both theoretically aim to recreate music as accurately as possible, there's a huge difference in terms of their approach. Pro gear tends to be no-nonsense, straight-to-the-point in terms of design ethos, while the same can't always be said for audiophile-oriented devices.

Conversely, Pro gear doesn't necessarily concern itself with aesthetics or usability for the average home user – a rack-mount form factor, huge array of blinking LEDs, and a dozen BNC inputs/outputs aren't exactly what most audiophiles are looking for. Still, there's often enough overlap to where certain products have achieved crossover appeal. The Benchmark DAC1 being the first example that comes to mind, though there have been many others. And when it comes to sonics, the potential is certainly there. I remain of the opinion that the old Pacific Microsonics devices still make world-class sound, regardless of which market they fit into.

This brings me to RME and their ADI-2 DAC https://www.rme-usa.com/adi-2-dac.html. The evolution of this model actually seems relevant to the above discussion. RME launched the the original ADI-2 well over a decade ago which was very obviously a studio-oriented design. Then came the ADI-2 Pro ($1,999 USD) in 2016 which became popular with audiophiles. It was just convenient enough for home users to take advantage of, while design choices like TRS jacks and ADC functionality reminded users of its pro roots. It was certainly usable in an audiophile setting, but required a few workarounds such as adapters for RCA connections. 

RME must have taken the hint and released the ADI-2 DAC ($999 USD) with a focus more towards traditional home hi-fi. The device keeps the audible magic which folks enjoyed from the Pro (and even upgrades some aspects) whilst giving a more traditional suite of inputs/outputs and omitting the analog-to-digital stage altogether. Also worth noting is the price, which is chopped in half compared to the Pro model.

Despite its heritage, the ADI-2 DAC ends up being a fairly "standard" compact DAC/headphone amp unit. I've had at least a dozen generally similar devices pass through my system over the past couple years. Most of the usual features are here: RCA plus XLR outputs, volume control (including a handy remote), headphone output, and a DSD-capable USB input along with the standard coaxial and Toslink options. The system is powered by an external 12V switching power supply, and a color front panel display keeps users in the know about things like incoming sample rates and volume levels. Overall, it's not the most feature-packed DAC/amp unit I've encountered, but it covers enough bases that I don't really have any complaints... and the EQ option is a unique/welcome feature, as I'll discuss shortly.

Internally, the ADI-2 DAC features some proprietary RME solutions combined with solid general design all around. The DAC section is centered around the excellent AK4490EQ chip from Asahi Kasei Microdevices, or AKM for short. While I'll be the first to point out that implementation is everything... I have to admit that devices utilizing the AK44XX series chips tend to have a natural, organic quality to them which I find really appealing. RME supports that AKM DAC with a Xilinx Spartan-6 FPGA plus a powerful DSP chip, both doing proprietary things for our benefit. Their SteadyClock FS promises extreme clocking accuracy through a combination of direct digital synthesis and analog phase-locked loop, both referenced to the "lowest phase-noise oscillator currently available.” I won't go into the technicalities but RME claims it is as good as, or better than, any so-called "Femto" level designs on the market. I get the impression that the designers don't love the marketing aspect at all, yet acknowledge it as a necessary evil in selling their gear – see this humorous thread on the RME forum for an example of their engineers being engineers. 

RME's deviates from the norm when it comes to adjustability; there's quite a bit of it to be had here. The selectable digital filters are built in to the AK4490EQ DAC chip itself, and thus not totally unique. But it's the DSP chip that unlocks the magic. A five-band parametric EQ, adjustable crossfeed for headphone listening, and the ability to save configurations as easily-selectable presets. Want the "sharp" filter, with moderate crossfeed, plus a gentle bass boost for a certain headphone? Go ahead and save that preset. How about the "short delay slow" filter with no crossfeed and a notched EQ to tone down a specific frequency region in the highs of another headphone? That can be done as well. Even those of us with way too many pairs of headphones/speakers are well served by the little ADI-2 DAC, as the device is very generous with the number of saves available. While perhaps not being the most intuitive control system I've ever used, I found myself pretty comfortable with the adjustments after a bit of practice.

Overall this is a unique and feature packed DAC/headphone amp that sells for a very competitive price.... yet none of that matters if the sound quality isn't where it should be. Did RME sacrifice performance for the sake of a large feature list? Read on to find out.

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)