RME ADI-2 DAC FS Review

I’m a DAC junkie. Sure, DACs fall far behind speakers, headphones, and (of course) source material in importance. Amps, too, probably outrank DACs in the audiophile hierarchy. But a DAC is, quite literally, a system’s link between the digital and the analog world, and a poor DAC can squeeze the life out of an otherwise solid system. 

But there’s danger in writing DAC reviews. There are those “objectivist” audiophiles that insist that all “properly designed” DACs sound the same. If someone claims that he or she can hear differences between “properly designed” DACs, two questions inevitably, and quickly, follow: Was the listening level matched? Was the listening blind? If the answers to both questions are “yes,” the results are nonetheless dismissed.

For those who insist that all “properly designed” DACs sound the same, the best advice I can give is to stop reading now and purchase one of the many sub-$100 DACs that measure near “perfection.” (The $99 Schiit Modi 3, discussed later in this review, would be my recommendation, thanks to Schiit’s excellent customer service and bulletproof warranty.)

For everyone else, this is a review of the RME ADI-2 DAC FS (U.S. MSRP $1,099), a DAC that’s been highly praised by both “objectivist” and “subjectivist” (or, perhaps, realist) reviewers. After living with the ADI-2 DAC for several months, I discovered the device’s strengths and weaknesses and came to appreciate its versatility and build quality.  

Physically, the ADI-2 DAC is an unassumingly impressive device. Whereas many audiophile DACs these days are hulking, the ADI-2 is a mere 8.5 by 2 by 6 inches. Despite its diminutive size, it’s solidly built, with a metal body and reassuring heft. Perhaps the only part of the ADI-2 that feels less-than-substantial is the slim plastic remote control. But it’s functional, and a remote of any kind is a welcome addition for those who plan to use their DAC beyond arm’s reach.

At first glance, the most striking element of the ADI-2 DAC is the array of buttons and knobs packed onto its small face plate. At left is a flush, soft-push power button surrounded by an LED halo, which lets you know the unit’s power status. Moving right, there’s a 1/4-inch headphone jack, spec’d at an excellent .1-ohm impedance, and a 1/8-inch IEM jack. Further to the right is where things get complicated. 

I’ll leave it to RME’s extremely detailed (and commendably readable) manual to explain it all, but the ADI-2 DAC’s right side is crammed with an LED-ringed volume knob, four vertical buttons (VOL, I/O, EQ, and SETUP), a small display screen, and two smaller vertical knobs. By manipulating this panoply, the ADI-2’s user can do everything from selecting the input source to setting the output volume to collapsing the signal to mono to tweaking the perceived stereo width to inverting the signal’s polarity, among other options. Most importantly, at least in this reviewer’s opinion, the ADI-2 DAC includes a five-band parametric EQ and five DAC filters (Short Delay Sharp, Short Delay Slow, Sharp, Slow, NOS). 

The ADI-2 DAC’s many options (and I haven’t even mentioned them all) gives the device a sort of Swiss Army knife of audio vibe. (It’s a DAC! It’s a headphone amp! It’s a preamp! It’s an equalizer! Etc.) The ADI-2 even has a setting that, after downloading a few WAV files from RME’s website, lets the user test that his or her playback is bit perfect. 

Like a Swiss Army knife, even if one doesn’t intend to use all of the ADI-2 DAC’s tools, it’s nice to know they’re there.

The comparatively straightforward rear of the ADI-2 DAC features USB and both RCA and Toslink optical digital inputs, balanced and RCA analog outputs, and a locking connector for the external power supply. 

For most of my listening, I used the USB input from my Mac Mini, playing tracks from Audirvana (which, thanks to the RME, I now know is a bit-perfect setup). For using the RME as a DAC feeding my other amps, I set the output level at +13 dBu and used the Sharp filter (more on this selection later). 

The ADI-2 DAC’s default screen displays the device’s output and volume, the file’s sample rate, and a (very visually pleasing) frequency analyzer. 

Before tackling the ADI-2 DAC’s performance as a DAC, it’s worth addressing three features that I regard to be the ADI-2’s most unique for a DAC its price: 1) its headphone amp, 2) its parametric EQ, and 3) its ability to serve as a preamp.

My initial listening to the ADI-2 DAC took place through its own headphone amp. And, as a result, my initial reaction to the ADI-2 was one of disappointment. The ADI-2 DAC’s headamp has a decidedly low-fi sound. Listening to Bob Dylan’s elegiac “What Good Am I?” from the 24/96 edition of Oh Mercy on Qobuz on my (previously reviewed) Brainwavz Alara, the ADI-2’s headphone amp comes across as dynamically compressed, tonally skewed, and lacking in both depth and width.¹ When the track was supposed to thump, it plunked. Dylan’s twangy guitar sounded oddly processed, and Malcolm Burn’s cheesy-yet-lovable keyboards were pulled to the front of the mix, rather than set to the back. As I cycled through other headphones, those characteristics held. Kicking the ADI-2’s headamp into “Hi-Power” mode may have ever-so-slightly improved the dynamics, but little else. 

After this underwhelming introduction to the ADI-2, I wondered whether the issue was the headphone amp or the DAC itself. Using the ADI-2 to feed a variety of external headphone amps, I quickly discovered it was the former. Routing the ADI-2 DAC’s outputs to my Schiit Ragnarok and using it to power the Alara, the situation improved dramatically. The dynamics, tonality, and soundstage I expected on “What Good Am I?” returned. But it didn’t take the Schiit’s top-of-the-line headphone amp to reveal the ADI-2’s amp’s shortcomings. The budget-minded Monoprice/Alex Cavalli Liquid Spark ($109.99 US MSRP) also put the ADI-2’s headamp to shame, at least to this reviewer’s ears. All told, I decided that it’s best to view the ADI-2 DAC’s headamp as a nice, if underwhelming, “bonus” feature — a point of view that eliminates the ADI-2 as a knockout AIO (all-in-one) unit, but that seems reasonable given that most of the ADI-2’s competitors don’t include a headamp at all.

While the ADI-2’s headamp disappointed, it’s parametric EQ didn’t. As someone obsessed with finding versions of albums that got the sound right at the mastering stage, I generally avoid equalization. Digital EQ, in particular, can sound grainy to my ears. However, the ADI-2’s parametric EQ proved to sound surprisingly analog unless pushed to unreasonable extremes. With the ADI-2, I found myself slightly tweaking albums that lack a good mastering in ways that were unambiguously enjoyable and unobtrusive. 

Likewise, when used as a preamp for an external power amp, the ADI-2 proved to be limpid, lacking all of the flaws of its headamp. Its smooth volume control also lacks the artificiality of some digital preamps. Because its digital, the ADI-2 DAC offers perfect channel balance, and its .5 dB volume increments allow for precise fine-tuning regardless of the power amp’s gain. 

Thus far, the ADI-2 DAC is two for three on its most intriguing (for the price point) features. But how does it fare as a standalone DAC?

The ADI-2 DAC uses AKM’s AK4490 chip. So to assess its sound (and value) as a DAC qua DAC, I pitted the ADI-2 against two other AKM-based DACs positioned at two very different price points: the Crane Song Solaris (U.S. MSRP $1,949), designed by the legendary Dave Hill, and Schiit’s budget DAC, the Modi 3 (U.S. MSRP $99). The former also functions as a preamp and includes a headamp (excelling at both); whereas the latter is plain vanilla DAC.

For this comparison, all of the DACs were fed into my Schiit Ragnarok amp. I used the balanced outputs on the ADI-2 and Solaris and the only outputs (single-ended) on the Modi 3. Listening took place on both headphones and speakers.²

As mentioned above, the ADI-2 DAC offers a variety of filter options to the user. Like most minimum phase filters, both the Short Delay Sharp and Short Delay Slow filters sounded somewhat artificial and “digital” to my ears. The NOS filter was fun to play with, but while it had a little of the appealing tonal density that some NOS DACs are known for, it came at the price of a significant loss of detail. Both the Sharp and Slow filters sounded good to my ears, with the former having somewhat more detail and the latter sounding somewhat more natural. In regular use, I could see myself bouncing between the Sharp and Slow filters, but for purposes of comparing the RME against the Solaris and Modi 3, maximizing detail seemed to be the more important priority, so I went with the Sharp filter. 

Keeping with the Dylan theme, I pulled up the hi-res edition of Blood on the Tracks in my Audirvana library and put the DACs through the paces, eventually zeroing in on short 10- to 20-second snippets of specific songs. 

My first reaction was that these are all quality DACs that get the most important things, such as timbre, correct. Nonetheless, there exist notable differences in other areas of presentation. 

Listening to “Simple Twist of Fate,” I was impressed by the $99 Modi 3. It had excellent front-to-back depth, but exhibited a bit of grain, especially in the treble. Moving to the ADI-2, the soundstage got slightly shallower. This relative lack of depth made the reverb on Dylan’s voice and overall “room sound” less apparent through the ADI-2. However, the ADI-2 surpassed the Modi 3 in smoothness, overall detail, and “blackground.” Instrument placement, left to right, was clearer on the ADI-2 than the Modi 3 and, overall, music sounded more lifelike through the ADI-2. Listening to the same segments of “Simple Twist of Fate” through the Solaris and moving back and forth between the DACs, the Solaris’s superlative detail retrieval was apparent immediately. The Solaris also took the ADI-2’s superior imaging and improved it even further, providing ultra-precise placement of instruments in the soundstage. Overall, the Solaris combined the best elements of the Modi 3 (depth) and ADI-2 (detail and smoothness) but simply did them all better. 

Moving forward a year in Dylan’s catalog, Desire’s iconic opener “Hurricane” further illustrated the differences between these AKM-based DACs. Through the Modi 3, each hit of Howard Wyeth’s propulsive snare is rendered as an indistinct thwak. Through the ADI-2, small details are somewhat more apparent, and the overall sound is more realistic. Reaching the Solaris, the distinct sounds of the snare head and wires are both clear and smooth. The same pattern repeats itself with the string articulation on Scarlet Rivera’s sinuous violin. 

In short, the Modi 3 is an excellent DAC for $99. But its grain gives it more digital sound, and it leaves some detail unresolved. The ADI-2 offers more detail and smoothness, despite its shallower stage, and is clearly the superior DAC. The Solaris, for its part, simply outclasses both the Modi 3 and the ADI-2. Only when it comes to “blackground” might the ADI-2 ever-so-slightly exceed the Solaris, but when it comes to detail, depth, smoothness — virtually any other trait one can think of — the Solaris is the better DAC.

So where does that leave the ADI-2 DAC?

In the end, the ADI-2 is very fine sounding DAC with excellent build quality and oodles of features. Whether it’s the right DAC for you depends on whether you intend to use all of its features and which ones you value most. 

If you don’t intend to use the ADI-2’s equalizer, play with its filter options, or use it as a preamp, but you do want a good headphone amp, the Modi 3 plus one of the many quality sub-$125 heaphone amps out there is probably a better, and more economical, choice. 

But for someone who loves all of the ADI-2’s bells and whistles (and plans to use them), the ADI-2 is a good choice. Even if the headphone amp isn’t the best, its serviceable, and the fact that the ADI-2 has both balanced and single-ended outputs means that it could be center of a system, simultaneously feeding an external headamp and providing a preamp for power amp and speakers without any cable swapping.

¹  All listening was done through Audirvana on my Mac Mini via USB output. Levels were matched within .2 dB for all DACs. But, no, my listening was not blindfolded. Or double blind. Or sextuple blind. And I’m okay with that.

²  Most listening was done on KEF Reference 1 speakers with an SVS SB-13 Ultra subwoofer. Headphones included Focal Clear, Sennheiser HD800S, and MrSpeakers Ether 2.

Product Information:

• RME ADI-2 DAC FS ($1,099)
• Alara Product Page
• Specification Sheet (PDF 143K) 
• User Guide (PDF 1.1MB) 

About the Author

Josh Mound has been an audiophile since age 14, when his father played Spirit's "Natures Way" through his Boston Acoustics floorstanders and told Josh to listen closely. Since then, Josh has listened to lots of music, owned lots of gear, and done lots of book learnin'. He's written about music for publications like Filter and Under the Radar and about politics for publications like New Republic, Jacobin, and Dissent. Josh is currently a postdoctoral fellow at the University of Virginia, where he teaches classes on modern U.S. politics and the history of popular music. He lives in Charlottesville, Virginia, with his wife and two cats.