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Review and Measurements of RME ADI-2 DAC

amirm

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#1
This is a review and detailed measurements of RME's new ADI-2 DAC. This is a spin off from their highly regarded ADC/DAC combo, the ADI-2 Pro. I have purchased the Pro for my testing but a member was kind enough to loan me the DAC only version reviewed here. I will measure and post any differences between the two at a later time.

The ADI-2 DAC retails for USD $999. The black version I received looks quite attractive with nice white LED highlights around controls and a high-resolution and highly responsive LCD display.

RME ADI-2 DAC Review.jpg

From a pure DAC functionality, it is better executed than my ADC/DAC. It has a remote control and unlike mine, has proper inputs for S/PDIF as opposed to a dongle.

The unit has huge number of settings and display material that is navigated through four switches and three rotary encoder, all of which are "clickable." Unfortunately this also brings with it lots of complexity and non-standard operation. For example, the click mode of right two encoders are used to scroll up and down in a menu. What??? Why not rotate the knob to go up or down and click to select?

Simple things are not simple. For example, there should be a button dedicated for changing inputs with just a click. But what is labeled as I/O just gets you into menus where you have to navigate and try to change the input without changing something else.

Fortunately there is an "auto" mode for selecting the input and if that priority matches yours, then you are good to go.

From interface point of view, the USB is UAC2 class compliant. Due to an odd design choice however, this mode is almost useless unless you only play 44.1 kHz content. The DAC oddly only advertises one sampling rate to Windows upon plug-and-play detection. While you can change that to any setting you want through MADIFace control panel that comes with it, you cannot have access to more than one sample rate at a time!

This of course made software like Roon that I use throw up:

RME ADI-2 DAC Format Playback Roon.PNG


In this case I had selected 88.2 kHz and that is the only sample rate Roon sees as a result. Playing anything then forced format conversion to this rate.

I contacted RME customer support in US and seemingly this is the way it works. This is quite disappointing as I don't understand why this way of operation is useful at all.

What this means is that practically speaking, you need to use ASIO drivers to have flexible playback under Windows. I don't know how it works under Linux of Mac. Hopefully it is better than in Windows and plug-and-play works.

I purchased the ADI-2 Pro version in my quest to find the most perfect DAC I can. Previously I hoped the Exasound E32 was it, but it didn't turn out to be the case. So it was with a lot of trepidation that I plugged the ADI-2 DAC into my analyzer to measure it. If you are not familiar with my tests, I suggest reading my tutorial on audio measurements here: https://www.audiosciencereview.com/forum/index.php?threads/understanding-audio-measurements.2351/.

Let's see how she does.

S/PDIF Measurements
Since we are fortunate enough to have S/PDIF input here, I selected that because it allows all of my tests to be run automatically. In the next section, I will also show the USB performance.

Starting line is frequency response and channel matching:

RME ADI-2 DAC Frequency Response and Channel Match Measurement.png


Ruler flat down to 10 Hz as it should be, indicates DC coupled outputs. Reconstruction filter starts pretty close to 20 kHz which is fine. What was superb though was channel matching. No matter what I set the volume to, the two channels were smack on top of each other! I don't think I have ever seen them matching so well. Pretty nice engineering here to get the two channels to behave so closely.

This is what jitter and noise looks like at 24-bits/48 kHz. As usual everything other than the main tone at 12 kHz is unwanted:

RME ADI-2 DAC Jitter and Noise Measurement.png


Note that max level is far higher than that of Topping DX7s (retail: $499). So I dialed down the volume until it matched the Topping. As we see, the noise floor is an inconsequential 1 or 2 dB higher. There is also a tiny bump between 2 and 4 kHz. So a hair worse than Topping DX7s but again, not a concern at all.

Let's see what happens when we feed the DAC a 1 kHz tone and then filter it out to see what is left:

RME ADI-2 DAC residual harmonic distortion Measurement.png


Oh wow! The RME ADI-2 has much lower harmonic distortion than Topping DX7s. And what it has dies down by 8th harmonic whereas the Topping keeps going. The noise floor is again a bit higher but overall, this is another category of performance and well above Topping DX7s.

Note also freedom of low-frequency noise below 1 kHz, indicating exceptionally clean supply (external wall-wart is switching by the way).

As another comparison, let's see how it does against Exasound E32 which retails for 3.5 times as much:

RME ADI-2 DAC residual harmonic distortion vs Exasound E32 Measurement.png


Here, its second harmonic is higher than that of E32 but from there on, it is much cleaner and of course, doesn't have all that "hash" which Exasound E32 has at lower frequencies.

Continuing our distortion theme, let's look at intermodulation:

RME ADI-2 DAC Intermodulation distortion Measurement.png


We see that the ADI-2 DAC does better than both Topping DX7 and DX7s.

I know, I know, you want to see the famous linearity graph so here it is:

RME ADI-2 DAC Linearity Measurement.png


This is almost as good as it gets. My analyzer by itself is a hair cleaner but otherwise, we are talking about deviations that are much less than 0.5 dB.

USB Measurements
Here is the J-test when driven by Roon using ASIO drivers:

RME ADI-2 DAC Jitter and Noise over USB Measurement.png


Squinting, it might be a hair better than S/PDIF. Regardless, it definitely is no worse so S/PDIF measurements are representative of what the DAC can do.

Likewise, let's look at linearity:

RME ADI-2 DAC USB Linearity Measurement.png


Just as pretty as S/PDIF. :)

Headphone Output Measurements
The RME ADI-2 DAC has two output settings for headphones: high and low. I did all of my testing in high mode. Let's start with output impedance:

RME ADI-2 DAC headphone output impedance Measurement.png


I think they advertise 0.1 ohm output impedance which is close enough to what I measure (which is impacted by the wires and setup I use) at 0.45 ohms. This makes it suitable to drive any impedance headphone without fear of the amplifier changing its frequency response. This is of course much superior to Topping DX7/DX7s which clock at 10 ohms or so.

For power measurements, I chose to display the output voltage. This allows me to put all the graphs on top of each other as I change the load impedance. To get the power for any place on the graph, simply square the voltage and divide it by the load impedance. I have noted the same for the point clipping starts on the graph:
RME ADI-2 DAC THD+N vs Load Measurement.png


As you see, the output gets up to 10 volts or so which was their design criteria. As such power is healthy even when driving high impedance headphones.

The unit has current limiting and short circuit protection. It triggered when I tried to drive my 33 ohm dummy load so I had to reduce the level until it would output. That reduced the output power at 33 ohms. But that is still exceptionally loud. I am listening to my HE400i headphones as I type this at -30 dB!

Here is how it compares to Topping DX7s:

RME ADI-2 DAC THD+N vs Load vs Topping DX7s Measurement.png


As you see, where the Topping runs out of juice, the ADI-2 DAC keeps going and going.

Listening Tests
I did not do any comparison testing this time. May do more later. But did listen a fair bit using both my Sennheiser HD-650 and HiFiman HE400i. I was pleasantly surprised to be able to drive the former as loud as I wanted. The sound was excellent, with great resolution, absence of any noise, and lots of power.

Conclusions
Finally a product where you pay more and you get more! The DAC portion either matches or beats the Topping DX7s especially in harmonic distortion. But the best advantage comes from the headphone output of the RME ADI-2 DAC where we are talking about very low output impedance and lots of power. This eliminates the main (audible) weakness of Topping DX7s. Yes, you pay twice as much for it but at least we have a known option here for folks who can afford the extra dollars.

I am bummed by the single sampling rate mode of the Windows UAC2 driver. I am hoping RME reconsiders and fixes this. Until then, I cannot give my unconditional recommendation for RME ADI-2 DAC. If the driver issue doesn't bother you, then you can purchase this unit with confidence knowing that it is the best measuring DAC so far in my portfolio!

Kudos to RME for producing such an excellently engineered product.

-----

As always, questions, comments, recommendations, etc. are welcome.

If you like this review, please consider donating funds for these types of hardware purchases using Patreon (https://www.patreon.com/audiosciencereview), or upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
 
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Sythrix

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#3
Yes!!! My temporary insanity paid off!
 

SIY

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#4
I had a chance to run the ADI-2 Pro through a set of measurements- if not perfect, then as damn close as you'd want. Nice to see that the cheaper one looks just as good.
 
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#6
Nice! Someone I respect really likes this DAC. I shall share the news. :)

According to him, the best thing about this DAC is just the ridiculous number of features it has. It can easily be the center of an entertainment system.
 
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#7
I'm increasingly convinced the myriad USB/driver issues (UAC2 wise) @amirm seems to continually run into are due to either a fundamentally borked Windows installation or iffy laptop USB implementation. This is not helped by Microsoft's 15-years-late-to-the-party adoption of UAC2, I'm sure. But it is getting irritating to keep reading about class-compliant USB issues with various DACs that don't show up as problematic for, apparently, anyone else (myself included).

Either take the time to sort out your USB/UAC2 issues or stop commenting on them ... it's clouding otherwise valuable information.

Nice review though ... and nice to see RME delivering on performance.
 

DonH56

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#8
Any advice for him? Too bad he doesn't know anything about Windows... ;)
 

amirm

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#9
I'm increasingly convinced the myriad USB/driver issues (UAC2 wise) @amirm seems to continually run into are due to either a fundamentally borked Windows installation or iffy laptop USB implementation. This is not helped by Microsoft's 15-years-late-to-the-party adoption of UAC2, I'm sure. But it is getting irritating to keep reading about class-compliant USB issues with various DACs that don't show up as problematic for, apparently, anyone else (myself included).

Either take the time to sort out your USB/UAC2 issues or stop commenting on them ... it's clouding otherwise valuable information.
No, this issue is confirmed by RME support:

From the user manual Pg 39:

Sample Rate: Sets the currently used sample rate. Offers a central and comfortable way of configuring the sample rate of all WDM devices to the same value, as since Vista the audio software is no longer allowed to set the sample rate. However, an ASIO program can still set the sample rate.

Most hi-fi audio players for Windows support ASIO, this is preferred for bit perfect playback and proper handling of sample rate changes.

I see the same issue reported on other forums by other users. See: https://www.head-fi.org/threads/rme-adi-2-dac-thread.868015/#post-13973875
 
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#10
That's nice, in this case. You still clearly have some USB/UAC2 issues elsewhere, however - as shown by multiple instances of DACs you've tested having issues under the Win10/CE UAC2 support that work fine for other people. If they were broken for everyone (e.g. Hugo 2 works fine with UAC2 drivers for everyone I know) I'd assume it was a general compatability-with-Windows issue, but they're not.

I'd love to try and troubleshoot it with you, but I stopped using Windows for audio purposes when I left core back in 2008.
 
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#13

Sythrix

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#14
Note also freedom of low-frequency noise below 1 kHz, indicating exceptionally clean supply (external wall-wart is switching by the way).
Really happy about this. No need for a linear supply.

Glad they took the time to get the power delivery right.
 

mindbomb

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#15
What is the headphone amp chip in this? It looks basically perfect imo, assuming thd+n x frequency is flat.
 
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#18
will this sound better than the project s2 box ?
Who knows. You can try finding someone who's heard both, but he'll only tell you what he thinks.
 
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#19
I've been drooling over this thing for a while now. It's good to hear that it wasn't for nothing.
 
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