This is my second update of my review, that I write after using with my recently acquired Audio Technica ATH-E70 IEM. I have bot changed the stars, only added a comment.
I am using the ADI2-DAC as an audiophile, not a musician or a studio engineer. I understand that I am in the target of RME for this specific product and I shall review the product as a product designed for audiophile use.
I am using the ADI2-DAC to listen mostly to CD quality classical and modern recordings on my MacMini running iTunes or Audirvana, with AKG 702 or Beyer Amiron Headphones ; I also sometimes connect the ADI2 to my old Dual amp feeding medium quality loudspeakers. Most of my music is 44,1 khz/16 bits PCM, but I made a few trials with high resolution PCM and DSD. The purpose of these trials was to test DSD sound, not to test the ADI2-DAC, but I ran into some limitations of the DAC regarding DSD that I shall comment below.
I am very happy with the sound and given the rave reviews that this product has got, I have no doubt that it is top quality sound, though I personally never compared the ADI-2 DAC with a competitor in the same price range. Given the sound quality and given features offered by the ADI, like the low noise minijack output or the ability to crossfeed L and R channels, there is no doubt that the ADI-2 DAC offers a huge value ; it is arguably among the very best DACs and headphone amps below 1000 Euros, and probably even beyond.
But the ADI2-DAC has two limitations for a user like myself and therefore I have given it only 4 stars.
1 Interface complexity
Despite the very nice and comprehensive user manual, the ADI2 is quite complex to use. I find it non intuitive to browse through all the setting with the buttons. Obviously, the designer has been very smart to enable access to so much functions with such a little screen and only a few buttons ; but it may be too smart for regular folks like me and I frequently get lost in the menus.
2 Limitations with DSD
The ADI2-DAC is capable of playing DSD, but by default, DSD signals are converted into PCM before the digital to analog conversion. This seems to be necessary to control the headphone output volume which is done digitally by the DSP, not by the analog output stage. This PCM conversion is required because DSD signals cannot be processed at all, whereas PCM can. Furthermore, according to the manual, the ADI-DAC has not enough processing power to enable EQ, crossfeed and other functions with high sampling rate PCM. Therefore, in my configuration, it is more convenient to have Audirvana perform the DSD to PCM conversion on the Mac upstream from the ADI2-DAC. Thus, the DSD support of the ADI is of little interest when using the ADI as a headphone amp or preamp with require volume control.
The ADI2-DAC can be set to behave like a native DSD converter thanks to the Asahi Kasei DAC chip. But in this case, only the line output is available at fixed level and no DSP based function is available.
I understand that this is the consequence of a design trade-off which leads to a relatively low price and very great value of the ADI2-DAC ; but for those that really want to listen to DSD through headphones, to enjoy the supposed superior sound of DSD (I am wring supposed because I could not judge yet), another high quality headphone amp is required. And in this case, there is no benefit to have a DAC/Amp combo like the ADI2-DAC ; better by a cheaper DSD capable DAC without amp and DSP.
To summarize this point : the ADI2-DAc is of little interest to listen to direct DSD.
Fortunately, this is not the case for me since I only wanted to give a try to DSD. The ADI2-DAC limitations with DSD will even save me money since It makes it useless for me to pay the premium price for high resolution DSD downloads !
ADDENDUM: I have recently bought an Audio-Technica ATH-E70 IEM and tried to use it on the dedicated IEM output of the ADI2. The result is awful, because of saturation in the mediums and highs, even at reasonable volume. The ATH-E70, which works nice on the regular 3,5 mm jack of an old iPhone, may be partly responsible for the issue and may have an impedance mismatch with the ADI2. Still, I am not sure that the ADI2 is well suited to drive any IEM.
Last but not least, in the current market and especially for digital-audiophiles, it would make sense to bring out a product with LAN/Ethernet and UPNp/DLNA. No need for a full featured network player with Tidal, Qobuz and other services, since these apps run on the computer associated to the DAC. More and more digital-audiophiles use a NAS to store and stream music and a LAN+DLNA is the best solution to connect to the DAC.
