Professional audio equipment manufacturer RME has been around for a while, but finally established itself as a household hi-fi and headphone enthusiast name with the ADI-2 DAC FS. There are three members of the ADI-2 family: First, the ADI-2 DAC FS which is the one most targeted at home-audio and the one this review is about. Second, there is the ADI-2 PRO, which looks similar but most significantly adds an analog to digital converter (AD/DA). Third, there is the simpler AD/DA-capable ADI-2 FS, which also has a totally different front panel. There are several external and internal differences between the three units. The vast majority of home audio hi-fi enthusiasts should go for the ADI-2 DAC FS version. 

The ADI-2 DAC is a very advanced unit, featuring lots of rare features for a DAC, like a built-in EQ. The navigation system is as expected for a small screen with just a couple of multi-function buttons: A bit quirky, but totally ok. If you share a household with less tech-savvy people, you might find them a bit frustrated. It does, however, come with a nice and simplistic remote control.

The reason the ADI-2 has made such a buzz in the hi-fi world is, however, not the vast built-in functionality, but the sound quality. This review will of course have a special emphasis on the headphone amplifier section. 

DAC SECTION 

If you take a look around the web, you will find some very good measurements of the ADI-2´s DAC section. That is a very promising start, but how does it compare to other DACs when you compare them by ear? Here are  my impressions. 

RME ADI-2 vs. Audio-gd Master 7 

First, I compared the RME-ADI-2 to my personal reference DAC, the smooth, yet detailed sounding Audio-gd Master 7 DAC, which is an old school R2R design. I hooked it up along with the ADI-2 to my Audio-gd Master 9 headphone amplifier, using the Sennheiser HD800 and Beyerdynamic T1 mk2 headphones. Even though these DACs are of very different design, the differences in this setup were so subtle I barely could identify them.  

Moving on to my most resolving headphone rig, the Stax 007tII energizer/amplifier with the Stax SR.009 headphones, the differences were still quite subtle, and only really noticeable on certain tracks. Female voices tend to be portrayed with an extra dose of midrange sweetness with the Master 7.  Still, it is something you have to listen closely for, and the difference in tonality is smaller than with, for example,the excellent Mytek DACs I have tested earlier. The RME is thus remarkably close to my personal reference DAC – but not identical. The NOS filter on the RME makes the tonality even closer, but the extra sweetness induced with the filter is sweet in a slightly “muddy” way, to put it coarsely, compared to the Master 7. However, we are talking minor, minor differences. There is nothing “muddy” about the RME, but nitpicking, the Master 7 does a hair or two better. 

Going back to the Master 9 amplifier, I plugged in the Hifiman HE1000v2, which is more revealing than the HD800 and Beyerdynamic T1 mk2 I used before. I found the same differences as with the Stax rig. The two DACs appear very similar in resolution and general tonality, and the only place I find what I would call significant differences is on some tracks with predominantly female vocals. 

Generally, I am amazed how similar the RME-ADI2 is to the Audio-gd 7. The detail level feels the same, and the tonality is very similar. As I really love the tonality of the Master 7, this is, of course, a very welcoming thing. The Master 7 still is the king of vocals, but the difference is very small, and in every other respect, they are hard to distinguish. Most importantly, though, I really need a higher-end headphone like the HE1000v2 or the Stax SR-009 to be able to tell them apart. 

RME ADI-2 DAC vs Violectric V800 

Having established that the ADI-2 is really close to my reference DAC, I don’t spend too much time comparing it to “lesser” alternatives. But the V800 is still no slouch, and in absolute terms, the V800 is surprisingly similar to the ADI-2. Tonality-wise, they are very close. A bit more detail and clarity is sometimes apparent with the ADI-2. I compared them using the coax/SPDIF input of the V800.

ADI-2 DAC vs Mytek Brooklyn Bridge and Brooklyn DAC+ 

The Mytek Brooklyn Bridge is basically a Brooklyn DAC+ with a streamer module, including a LAN input and a corresponding Wi-Fi antenna. Both the Bridge and the DAC+ offer analog inputs that can be used with normal line-level analog sources or as a phono preamp input (MM/MC). Compared to the ADI-2, the DAC+ most significant advantage is that it has that analog turntable ready input and a corresponding (and possibly better sounding) analog volume control. 

I compared the DAC section of the Bridge and the ADI-2 by hooking them both up to my Stax SR-009/SRM-007tII setup. I used the streamer input of the Bridge and the USB input of the ADI-2 (with the Allo USB Bridge), but also tried using both DAC´s fed by a coax/SPDIF signal. The results between them were consistent, no matter the digital input. 

First, I listened to the final part of Mahler’s 2nd symphony and noticed that the Mytek did a tad better with the most busy parts. The harp was clearer in the background with the Mytek. Moving on to other music, I tended to find them very similar, but the Mytek sometimes slightly clearer sounding and seemingly offering a tad more resolution with cymbals and instruments that have much treble presence. However, they are both brilliant, and mostly they are hard to separate, even on a very resolving Stax setup. 

Digital Inputs of the RME ADI-2 

The ADI-2 offers three digital inputs: SPDIF coaxial (RCA),  SPDIF optical (Toslink, ADAT compatible), and USB (768 kHz, DSD compatible). 

Sometimes DACs sound better with one input over the other playing the same file. I did some brief A/B listening comparing the coax and the USB using Roon and various formats. For comparable results, I used my digital transports from Allo (USB Bridge and DigiOne) to test for differences between the USB and SPDIF/coax inputs. When comparing them directly, I could not tell them apart. Feeding the USB input by my MacBook Air however, I do find the DigiOne-fed coax to be better. It is but not by much, and it is expected. Computers aregenerally more noisy than dedicated digital transports. 

HEADPHONE AMPLIFIER SECTION

It was obvious from the moment I plugged my first headphone into the RME ADI-2 that it performs above its price tag with headphones. 

RME ADI-2 vs Mytek Bridge/DAC+ 

I did a longer comparison which I will post in my upcoming review of the Mytek Brooklyn Bridge. In the meantime, here is my conclusion. Both the ADI-2 and the Mytek Bridge/DAC+ have excellent headphone amplifier sections. They present lots of detail, with the power to back it up. Often, they perform similarly good, but when one of them stands out, it is the Mytek. It is a bit more punchy and has a livelier midrange presentation. Both have lots of power and offer a spacious and detailed presentation. 

RME ADI-2 vs SPL Phonitor xe 

I used the ADI-2 as a DAC for the SPL Phonitor in this comparison. 

I start out with Nils Petter Molvær´s “Gilimanuk”, and I find the ADI-2 to be clearer and crisper. The Phonitor is good in another way, though. It feels more intimate and enveloping, but less spacious. Moving on to different music, the impression remains the same. With harsh recordings, like MIA´s “World Town”, the Phonitor is significantly less bright and coarse sounding, thus nicer to listen to.  I find both units very good. It is slightly easier to hear fine detail with the RME. The Phonitor is a bit fuller sounding and adds more “meat to the bone” of the instruments. 

Sennheiser HD650

I think the Phonitor drives the HD650 very nicely and am surprised that the ADI-2 is just as good, or even better, depending on your taste. The Phonitor is bolder and thicker, the ADI-2 a little crisper, but also more open sounding. 

Beyerdynamic T1 mk2 

With “Don’t know why” by Norah Jones, the T1 mk2 is a lot more pleasant to listen to with the Phonitor. The ADI-2 becomes a bit dry and soulless.  With instrumental music, the difference is smaller, but I definitely still prefer the Phonitor with theT1 mk2. 

Sennheiser HD800 

Playing the same Norah Jones track as above, I find the same result (to a lesser degree): The Phonitor is simply a more pleasant listen. Generally speaking, it has a preferable tonality and roundedness. But the ADI-2 holds up very well, and you do not lose any detail compared to the Phonitor. All in all, the ADI-2 is an impressive unit with the HD800. 

Shure SRH-1840 

I found the SRH-1840 to be an insanely good match with the Phonitor, and although it sounds good by itself, the ADI-2 is way behind. Mostly it sounds thinner, lacking in body and musicality. Details are all there, but not that magic presence that the Phonitor has to offer. 

Hifiman HE1000v2

The ADI-2 does an OK job, but compared directly, there is no doubt that I prefer the Phonitor. It generally plays well with the HE1000v2 also and sounds fuller and meatier, more neutral. The ADI-2 gets a bit thin sounding. The detail level on the ADI-2 is great though, at least as high as the Phonitor. 

DAC Comparison: Comparing the ADI-2´s DAC output vs the xe´s built-in DAC using the Phonitor xe headphone amplifier combined with the HE-1000v2, I find the ADI-2 DAC to be clearer sounding, but not really by a big margin. The slightly forgiving character of the Phonitor amp might take some credit/blame for that. 

Depending on the headphone, the ADI-2 holds up very well, and in many cases I find my preferences to be a subjective matter, mostly about whether I prefer the cleaner and brighter sound of the ADI-2, or the bolder and warmer sound of the Phonitor. However, when there is a clear preference, it is for the Phonitor.

RME ADI-2 vs Questyle CMA800R 

I used the ADI-2 as a DAC for the CMA800R

HD650 

First out is “So In Love” with the Jacob Brio Trio. The detail level feels similar, but the Questyle has more soul and body. It is warmer and more “musical”, the RME gets a bit more clinical sounding. In direct comparison, that is. In itself it sounds really good, it is just that the Questyle is even better. 

Sennheiser HD660S

The ADI-2 is also fabulous with the HD660S. The Questyle is, however, slightly sweeter and fuller sounding, yet it feels just as transparent and spacious. But considering the Questyle is twice the price and doesn’t have a DAC, the RME ADI-2 is impressive. 

Sennheiser HD800  

Both are great with the HD800. The Questyle is a bit more rounded, smooth, and natural sounding, while the ADI-2 is a bit flatter and drier sounding. I prefer the Questyle, but could definitely live with the ADI-2. 

Oppo PM1 

Both do well, the difference is similar as above, but to a lesser degree. 

Audeze LCD-X 

Both are good, but the Questyle is more organic sounding, and handles complex passages with more ease. 

Hifiman Sundara

The Questyle has a bit more organic warmth; it is a bit more delicious. But the ADI-2 sure gives it good competition. 

Beyerdynamic DT1770PRO

As above, the ADI-2 does a very nice job, but the Questyle is more organic sounding

Beyerdynamic T1 mk2

The 600 ohm T1 mk2 is more differentiating than most headphones, and the Questyle comes out clearly on top. It has a more organic presence, especially in the treble. This performance mirrors what I found with the Phonitor – The T1 is not RE ADI-2´s best match. 

Concluding, the ADI-2 holds up well, compared to the Questyle. In short, my results are generally similar when compared to the Phonitor. The RME fairs well compared to the Questyle, but it is not all the way up there. The Questyle offers some extra warmth and fullness while not losing any of the detail. For the price, however, the ADI-2 delivers the goods with bravour. It is very impressive. 

RME ADI-2 vs Auralic Taurus 

The Taurus has a “balanced mode” and a “single-ended mode”. They sound slighlty different, so I have indicated whenever I used the balanced output of the Taurus. I used the ADI-2 as a source for the Taurus.

Sennheiser HD800 (balanced) 

The RME and the Taurus are very similar in both sound signature and detail level. I am truly impressed with the little thing. When I prefer one over the other, it is the Taurus, but to be honest, they are incredibly close. 

Audeze LCD-X and LCD-3 (balanced)

The Taurus always played beautifully with the Audeze LCD-series. The ADI-2 has a similar performance, but I do prefer the Taurus, it has that extra tad of headroom and authority. 

Hifiman Sundara (unbalanced)

RME does a great job, and honestly, I find them too similar to recommend one over the other.  

Sennheiser HD660S and HD650 

Both sound great on both amps, and almost identical. 

Sennheiser HD700

Unlike the other Sennheisers I tried, the HD700 does sound significantly better on the Taurus. It is smoother and more natural. 

To conclude, the RME ADI-2 gets absurdly close to the highly regarded Auralic Taurus. As always, it depends a bit on the headphones used, but they have quite a similar sound signature. 

RME ADI-2 vs Schiit Asgard 2 

Unlike the above comparisons with amplifiers costing more than the ADI-2, the Schiit Asgard is a fraction of its cost. I used the ADI-2 as a source. 

Hifiman Sundara 

I certainly prefer the ADI-2. It is more detailed, with better depth and space. The Asgard has a bit more weight, a bit meatier sound. 

Sennheiser HD800 

The ADI-2 feels a bit more polite, a bit “glassier”. With bad recordings, the Asgard 2 is more forgiving, but otherwise, I prefer the ADI-2. 

Beyerdynamic T1mk2 

I have found the ADI-2 to underperform with the 600 ohm T1mk2. The treble becomes a bit flat, and it generally sounds a bit dry. Although lacking a bit in detail retrieval, the Schiit is a better match to my ears. 

Beyerdynamic DT1770PRO

The ADI-2 does better with the DT1770PRO, though. Again, it is more transparent than the Asgard 2 but has less body and weight. 

Audeze LCD-X 

As stated before, the ADI-2 does a very nice job with the LCD-X. The Asgard 2 is nice too but lacks a bit in regards to detail retrieval. 

RME ADI-2 vs Violectric V200 

The Violectric V200 is a long-standing reference headphone amplifier for many. In this brief comparison, I used the ADI-2 as a source. 

Audeze LCD-X 

Even though I always liked the V200 with the Audeze LCD-series, I  find the ADI-2 to perform even better than the V200. It is even clearer and more natural sounding. The V200 is a bit toned down, lacking some of the extra sparkle and liveliness. I don’t find the V200 dull or muffled on its own, but the ADI-2 is in direct comparison more alive sounding. 

Focal Elear 

With the Elear, I find the ADI-2 to sound clear, crisp and organic, whilst the V200 is a bit flatter sounding in direct comparison. I am truly impressed with the ADI-2.  

Sennheiser HD800 

Also, with the HD800 I find the ADI-2 to have more bounce and virility. As good as I think the V200 is, the ADI-2 is even better. 

The V200 has been my reference for a long time, and I wish I had not gotten a bit short on time. But it seems clear that with the headphones I tested, the RME ADI-2 was at least on the level of the V200, which as a standalone amp, costs roughly the same as the ADI-2. 

CONCLUSION 

The RME ADI-2 is a fabulous product. It rivals more expensive dedicated DACs, and at the same time drives most headphones just as well as similarly priced dedicated headphone amplifiers. In short, you get two for the price of one. The DAC section is not only extremely detailed, but has a nice touch of sweetness to its tone. The headphone amplifier sounds powerful and transparent. 

There is no such thing as a perfect headphone amplifier. As always, there are even better-sounding amps to be had for more money, and different sounding amps for less. However, few headphone amps give you the flexibility of the ADI-2 with its selection of filters, tone controls and EQ.

As a DAC alone, this unit should be on anybody’s list. If you want a DAC/amp for your headphones, it is a killer.

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Selected music

Kattorna – Tomasz.Stanko Quintet

Grand Central – Tomasz

Aoms For Peace – Thom Yorke

THis mEss We´re in – Thom Yorke/PJ Harvey 

Holberg Suite – 1B1 

Grounds Entrance – Jeff Ballard

Undertow – REM

You Remind Me – Little Hurricane 

Your Turn – Marc Ribot´s Ceramic Dog 

Turning Point – Tord Gustavsen Trio 

Summer – Mogwai 

Ting – IPA 

Camino Piedroso – Ambrodavi

Specifications

Inputs 

1 x USB 2.0 (USB 3.0 compatible)

1 x SPDIF Input coaxial

1 x ADAT or SPDIF Input optical

Outputs 

1 x RCA Analog Stereo Output unbalanced

1 x XLR Analog Stereo Output balanced

1 x Extreme Power Headphone Output

1 x Super Low Noise IEM Output

Digital Inputs Specifications

General

• Lock Range: 28 kHz – 200 kHz

• Jitter suppression: > 50 dB (2.4 kHz)

• Accepts Consumer and Professional format

SPDIF coaxial

• 1 x RCA, according to IEC 60958

• High-sensitivity input stage (< 0.3 Vpp)

• AES/EBU compatible (AES3-1992)

SPDIF optical

• 1 x optical, according to IEC 60958

• ADAT compatible

Analog Outputs

XLR

• Output level switchable +19 dBu, +13 dBu, +7 dBu, +1 dBu @ 0 dBFS

• Signal to Noise ratio (SNR) @ +7/+13/+19 dBu: 117 dB RMS unweighted, 120 dBA

• Signal to Noise ratio (SNR) @ +1 dBu: 115,4 dB RMS unweighted, 118,9 dBA

• Frequency response @ 44.1 kHz, -0.1 dB: 0 Hz – 20.2 kHz

• Frequency response @ 96 kHz, -0.5 dB: 0 Hz – 44.9 kHz

• Frequency response @ 192 kHz, -1 dB: 0 Hz – 88 kHz

• Frequency response @ 384 kHz, -1 dB: 0 Hz – 115 kHz

• Frequency response @ 768 kHz, -3 dB: 0 Hz – 109 kHz

• THD @ -1 dBFS: -112 dB, 0.00025 %

• THD+N @ -1 dBFS: -110 dB, 0.00032 %

• THD @ -3 dBFS: -116 dB, 0.00016 %

• Channel separation: > 120 dB

• Output impedance: 200 Ohm balanced, 100 Ohm unbalanced

Chinch

As output XLR, but:

• Output: 6.3 mm TS jack, unbalanced

• Output level 6 dB lower than XLR (-5 dBu to +13 dBu @ 0 dBFS)

• Signal to Noise ratio (SNR) @ +13 dBu: 117 dB RMS unweighted, 120 dBA

• Signal to Noise ratio (SNR) @ +1/+7 dBu: 114/116 dB RMS unweighted, 117/119 dBA

• Signal to Noise ratio (SNR) @ -5 dBu: 109 dB RMS unweighted, 113 dBA

Phones

As Cinch but:

• Output: 6.3 mm TRS jack, unbalanced, stereo

• Output impedance: 0.1 Ohm

• Signal to Noise ratio (SNR) @ +22 dBu: 117 dB RMS unweighted, 120 dBA

• Signal to Noise ratio (SNR) @ +7 dBu: 116 dB RMS unweighted, 119 dBA

• Output level at 0 dBFS, High Power, load 100 Ohm or up: +22 dBu (10 V)

• Output level at 0 dBFS, Low Power, load 8 Ohm or up: +7 dBu (1.73 V)

• THD @ +18 dBu, 32 Ohm load, 1.2 Watt: -110 dB, 0.0003 %

• THD+N @ + 18 dBu, 32 Ohm load: -107 dB, 0.00045 %

• THD @ +14 dBu, 16 Ohm load, 0.94 Watt: -110 dB, 0.0003 %

• Max power @ 0.001% THD: 1.5 W per channel

IEM

As Phones, but:

• Output level at 0 dBFS: -3 dBu, 0.55 V

• Signal to Noise ratio (SNR) @ -3 dBu: 115 dB RMS unweighted, 118 dBA

• Max power, 8 Ohm, 0.001% THD: 40 mW per channel

Digital

• Clocks: Internal, SPDIF In

• Jitter suppression of external clocks: > 50 dB (2.4 kHz)

• Effective clock jitter influence on DA conversion: near zero

• PLL ensures zero dropout, even at more than 100 ns jitter

• Additional Digital Bitclock PLL for trouble-free varispeed ADAT operation

• Supported sample rates for external clocks: 44.1 kHz up to 192 kHz

• Internally supported sample rates: 44.1 kHz up to 768 kHz

General

• Included power supply: external switching PSU, 100 – 240 V AC, 2 A, 24 Watts

• Standby power consumption: 120 mW (10 mA)

• Idle power consumption: 7 Watts, Max. power consumption: 18 Watts

• Idle current at 12 V: 570 mA (6.8 Watts)

• Dimensions (WxHxD): 215 x 52 x 150 mm (8.5″ x 2.05″ x 5.9″)

• Weight: 1.0 kg ( 2.2 lbs)

• Temperature range: +5° up to +50° Celsius (41° F up to 122°F)

• Relative humidity: < 75%, non condensing