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George 47

RME ADI-2 DAC

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And n’er the twain will meet.

Pro audio and domestic audio.

With both groups aiming for the best sound quality for the money, you would think there would be a lot of crossover products but that does not seem to happen. Pro Audio is seen as a group of people interested only in measurements, tuff boxes as the equipment will be given a rough life, with solid boxes costing 4p and of course, they are not that fussed over peripherals like cables or ultimate sound quality. Domestic Audio is seen as being all about pretty boxes, badly made audio, fluffy things like cables and connectors with endless fussing about non-existent sound quality differences achieved by ultra-expensive foo nonsense. And n’er the twain will meet.

But occasionally a cross-over product comes along that works in both camps.

RME is a well know German pro-audio company with a great track record of equipment used in recording studios. They have a strong focus on high value. They started business in 1996 and the team are either musicians or sound engineers so they should know about good audio. With such a strong pro audio background there are lots of measurements and technical discussions on their web pages. And surprise, surprise they do seriously listen to their products during development.

The product here for review has become something of a ‘darling of the moment’ product. Unfortunately, the problem with the t’internet is that some darlings come and go very quickly especially in computer audio. The RME ADI-2 DAC is aimed squarely at the domestic market and is based on the PRO version released in 2016.  RME exchanged some of the Pro’s studio features for typical home and hifi ones. The operation of the ADI-2 DAC is simplified. The ADI-2 DAC focusses attention on the DA process and on headphone outputs with an output for In-Ear Monitors and one for Headphones. The IEM output is not aimed at those silly little white earbuds that Apple give away free (I am surprised they can even give them away) but proper ear monitors.

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The half-sized case is very well built and has inputs for SPDIF coaxial, SPDIF optical (ADAT compatible) and it has USB to RCA, XLR, TRS and mini-TRS. The ADI-2 DAC has balanced/unbalanced analogue outputs, an Extreme Power headphone output, a super low noise IEM output, SteadyClock FS, 4-stage hardware output level control, DSP-based signal processing, external power supply operation, Class Compliant USB compatibility and sample rates up to 768 kHz as well as DSD and Direct DSD playback. The SPDIF input signal can even be recorded via USB - the DAC is a true 2 channel Full Duplex audio interface. Phew, what a lot of inputs and outputs.

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The display, function keys, volume knob, even the standby button - all go off after 10 seconds of no user operation when AutoDark is activated. Touching any button or control will turn on all lights for 10 seconds.

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SteadyClock FS reduces the self-jitter of SteadyClock by improving its second, analogue PLL circuit, and referencing both Direct Digital Synthesis and PLL to a low phase noise quartz crystal. The low phase noise oscillator driving the updated circuit reaches jitter specs lower than a picosecond (ps), an area called FemtoSecond. Hence SteadyClock FS.

All of this is explained in the comprehensive 70-page manual, which is quite a read. All of these adjustments are made through various sequences using tiny 5 push buttons and three knobs on the front of the DAC, which can be set through rotation and pushing. The manual is worth a read but I found the YouTube videos explain how to actually make the changes and it is, therefore, more helpful.

I asked the designer Matthias Carstens some questions about the ADI-2 DAC and I found his answers gave a great insight into how he and the company works:

What DAC chip is used in the ADI-2 DAC (is it the AKM 4490?)

Yes.

and why did you choose that particular chip?

This is a bug-free, matured chip that doesn't cost a fortune but offers very good specs and features. It needs a special analogue output stage to shine, but that is (of course) where we excel :-)

How is the NOS DAC filter configured? Does it have no filtering at all, both digital or analogue, or is it ‘similar to NOS’. The output shows the harmonics from unfiltered audio but is some filtering done?

Yes, in the digital domain. As explained in the manual this is the Super-Slow mode from AKM. While it looks like NOS with Sines (stepped) and in frequency response (drop below 20 kHz), there is a very slight out-of-band suppression filter active, where real NOS would not have any filter.

Clearly, you are proud of the great measurements of the DAC but how important is listening in your assessment process of the design and execution of the ADI-2 DAC?

Very important, as that is what we later do with it - listen to music! In fact, in all the years of RME we several times ran into audible problems that were not found with measurements before. Of course, once you know there is a problem you will find the respective measurement later on that allows you to identify and quantify the issue. Meanwhile, the number of available/performed measurements fills a complete book alone, so chances are low that a fully measured/examined unit shows unexpected behaviour. Then again, some things you have to try and not rely on complicated measurement setups. How long is the mute time needed when switching from PCM to DSD? How fast can we switch sample rates within PCM? What are the best default settings to make Bass and Treble sound really good?

The Loudness function is a good example where listening alone was done to find and set all parameters, that was then poured into the DSP as options.

Does the ADI-2 DAC have precautions taken against noise (such as filters) that may originate from external input sources and the mains?

The ADI itself is fully noise- and hum-free. The inputs have HF-filters which prevent the analogue inputs (and outputs) to react on your Smartphone lying beside it (for example). The DC input is fully filtered and switch-regulated with additional super low-noise regulators (see the chapter about that in the manual). So, whatever you feed it there will be zero difference in the technical data and sound on all I/Os.

Is the ADI-2 DAC made in Germany or is it designed in Germany and built elsewhere?

Designed and built in Germany, by beautiful old men... :-)

And who said our German colleagues have no sense of humour!!

I found the comments on listening very interesting and not too dissimilar to those of Bruno Putzeys, designer of the nCore Class D amplifiers.

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Anyway, down to using the product. I set the DAC straight into my big system of an Audionote CD4T, AN 4.1x DAC, Pass Labs XP22, Pass Labs X30.8 and a pair of Audionote E Silver Signatures all connected mainly with Cut Loose silver ribbon cables. 

As the ADI-2 DAC is a half-sized box it was easy to accommodate in my rack. It is powered by a separated mains power block which is probably an SMPS, hence my question on noisy mains. It switched on without any problem. Setting up is a different issue. Reading the manual is great for getting information about the product and the various functions but the YouTube clips were more informative about how to actually make it happen. And so, I set it up with the SPDIF coax from my Auralic and RCA output to the Pass Labs XP22. I used it with a -7db output to better match the XP22 inputs.

And on to listening, there has been a lot of discussion on expectation bias and mine was in full flow: a very technical product, lots of measurements, studio background….oh yes I have heard this type of product before….bright, shiny, lots of details and very wearing…..BUT NO.

The sound was neutral, 3D, with great clarity. In fact, I might even say it was on the warm side of neutral. Surprise 1. I tried my list of test tracks and my initial impression was reinforced. I could not hear any warm-up going on and the DAC was ready from the get-go. Surprise 2.

I then left the test tracks behind and just played the music that appealed to me at that time as opposed to being in reviewer mode with pen in hand and notebook at the ready. For me, that is a great sign as I am starting to enjoy the music.

I played Shelby Lynn singing A Little Loving, the Dusty Springfield song, and this gentle track had a great 3D soundstage (low noise?) with a really intimate recorded voice. Very close. But still human with a solid 3D image and not a paper-thin cardboard cut-out. I followed that with some Essie Jain from her All Became Golden album. A very close recording of her voice with some nicely recorded and naturally balanced instruments. They were all very clear, easy to hear with none of that mid-forward type of sound from other studio-based DACs. This was good. But how does it work with some really powerful bass? Onto Mussorgsky: Pictures at an Exhibition by Jean Guillou playing the Great Organ of the Tonhalle, Zurich. The organ sounded nicely 3D in a big environment. And when the bass pedals came in on I.Gnomus they are very deep and tight. I let the whole album play as it is such a good piece of music when played by a master on the great organ; and why not?

How about more modern music? James Blake’s Limit to Your Love. The piano sounded really nice with some great reverb and then the bass…….woah some really low synthesised bass that will really test your system. No problem here. OK on to some Led Zeppelin just to rock things out a bit with Dazed and Confused…..forget your audiophile sensibilities this is about a raw rock group with a powerful singer letting go on top of some powerful drumming and bass with a screaming guitar. With some DACs, it can be become a real mess but not here. Clear powerful rock.

OK, how about something that could set your teeth on edge? AC/DC. It’s a Long Way to the Top (If You Wanna Rock ‘N’ Roll). Compressed, bright, edgy…of course…that is the way it is recorded. It played with real drive and power. And I could hear all the words!! Shakespeare, this is not. But it all stayed together and driving even when the bloody bagpipes came in.

A little experimentation now with the filters. There are five filters including the one I started with, Sharp cut off and of all things a NOS filter, which is a very slow filter with some HF roll off. I really liked the NOS filter, not surprising as my Audionote 4.1x DAC is a NOS DAC and has no filters at all. The RME made the sound stage really 3D and warmed the sound up more than the Sharp filters, which could get a little stark with less good recordings. Unfortunately, I have a lot of less than brilliantly recorded music. The ADI-2 allows you to choose. So, for me, the Slow filter (Filter 4) and the NOS (Filter 5) got the most play.

I now felt I could do some comparisons and accepting that comparisons are odious it was pretty easy to say that the ADI-2 saw off my current references from Metrum Acoustic and two older Cambridge Audio DACs. Those three DACs are a little old but they play music really well and were my ‘instruments of choice’ for up to £1K DACs. This was getting interesting. How about the AN 4.1x DAC? Errr no there was a real margin here and the comparison was not sensible especially as the AN is £13.5K retail. But against my AN2.1x DAC I would say the AN was more to my taste but the ADI-2 could easily be preferred by others and I would not disagree.  This was not what I expected from a PRO audio DAC. Yes, the ADI-2 is a little dryer and a little more stark compared to my AN 2.1 x DAC but your preferences may be different and there is the small matter of a £2-£3K difference in price. 

One of the problems with reviewing on your own is that you can end up ‘breathing your own fumes’. So, I invited Bryan (Bryfiero) from the Wam over to hear the DAC. I did not say anything after a few tracks but he also preferred the NOS filter. Bryan also said he thought the ADI-2 DAC would have beaten the Metrum in the SQ stakes. He was so enamoured of the DAC I went around to his place a few days later and we heard it in a completely different system. Bryan has the Squeezebox Classic, Chord DAC 64, Karan Integrated and Vandersteen 1 speakers. His system was sounding really good in his room and had a very spacious sound ( a speciality of Vandersteen). We both preferred the Slow filter 4 or Filter 5 NOS. And against his Chord (used to sell at >£2K) it was very close with both of us understanding if someone else chose one over the other. A 2nd great result.

I tried using the ADI-2 DAC with its variable output straight into the Pass Labs XA 30.8. The system gave a good account of itself but I preferred my active preamp. Not a bad result as the Pass Labs XP22 costs over £9K. The sound through the Pass Labs had more drive and attack. However, this was such a good result I tried it into my Nord NC 500 power amplifier. This was a much better match and the system really worked. In fact, I can imagine a great set up of the ADI-2 + Nord + good speakers being a great and not too expensive system. Not surprised that Nord sells the RME with their amplifiers as they work really well together.

This is only about half of what this DAC can do. I got out my headphones to try out the headphone part of the DAC. My favourite headphones at the moment are Beyer Dynamics DT770s and they sounded excellent. They can sometimes sound a little weak or thin through some headphone amplifiers but not here and I could hear why they are favourites in studios. Impressive for those who can’t always use speakers. There was also a lot of other features including DSP, which I did not try as my system has a fairly flat response in my 30’x20’ room.

In conclusion, I was really surprised by the great sound quality of this DAC and it really shows that RME listening to their audio products is giving a great sounding product. Given it was better than my £1K references (already the best sub-£1K DACs I had heard) and it could be preferred to another twice as expensive, then I have to say it is very good value for money especially at its £850 price. It is solidly built and looks as though it will give many years of great service. I liked it and would have bought it if I did not already have 5 DACs. A great product and it will be well worth keeping an eye on these guys in the future.

Specifications: Please see https://www.rme-audio.de/en/products/adi_2-dac.php

UK Distributor: Synthax Audio : https://www.synthax.co.uk/

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