The bad stuff first:
The screen emits very quiet chirping noises when it's on (at least with the included 12 V power supply; I cannot hear any of those noises with a 15 V power supply but am still using the included one as they're only audible in close proximity to the device and because I'm using headphones as well as the auto dark mode most of the time (no noises when the screen is off)).
There's a low frequency hum audible with sensitive in-ears if the DAC is not grounded to another device or the wall socket (it's the electricity in the flat I live in according to RME; it's a rather easy fix and there's no hum when I ground the DAC).
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The good stuff:
Basically everything else.
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I wouldn't mind if it had more digital inputs (two of each would have been nice).
Comes with a nice remote control whose buttons and functions can be remapped in the DAC's settings.
Loaded with features and settings.
Is getting software updates with new features and bug fixes quite frequently.
Good built-in screen.
I like the way and look of how the on/off button and volume control dial are illuminated.
Fully parametric five-band EQ (sufficient amount of bands in most cases) plus quick bass/treble control (can be disabled and is fully configurable in the settings). Even individual EQ settings for each channel possible.
EQ can be saved as presets.
Menus and navigation seem logical and intuitive to me. At least I've become familiar with the navigation and operation since I bought the DAC, and got used to it quite quickly (in around two days or so).
Fully adjustable dynamic loudness feature.
Different crossfeed implementations available. I'm actually using it with in-ears more often than I expected.
Three screens (simple black screen with big volume indicator, status screen that shows info such as the inputs and sample rates, screen with spectrum analyser and volume meter).
No clicks/pops/other shit while unplugging and re-plugging the in-ears/headphones (thanks to relays).
Really nice: DAC remembers each setting for each output.
Lots of other stuff and settings (such as screen brightness and colour temperature, left/right balance, mono, different gain stages for the headphone and speaker outputs, automatic gain selection, digital filters, polarity inversion).
Compact.
I really like the design.
Good build quality. The three stepped digital potentiometers (bidirectional infinite rotation plus integrated push button) could feel more premium, though (they're slightly wobbly).
Nice remote control - buttons' accentuation point feels very well defined and crisp.
The two RCA outputs are sitting a bit too closely, which may limit some cables with thicker plug shielding.
Nice remote control - buttons' accentuation point feels very well defined and crisp.
The two RCA outputs are sitting a bit too closely, which may limit some cables with thicker plug shielding.
Sound:
The measured performance of the ADI-2 DAC is truly excellent, as proven by several independent sources with lab-grade audio interfaces (stuff that surpasses my basic recording gear that's mostly only really good for output impedance based frequency response deviations by far).
Volume Control:
The volume is controlled digitally.
Attenuation steps are perfect, precise 0.5 dB steps between +6.0 and -69.5, and vary and get coarser below that (-69.9, -70.3, -70.8, -71.2, -71.7, -72.2, -72.8, -73.4, -74.1, -74.7, -75.5, -76.3, -77.2, -78.3, -79.4, -80.8, -82.4, -84.3, -86.8, -90.3, -96.3, mute). I would have preferred an option for a constant scaling of 0.5 dB over the entire attenuation range between mute and +6.0, which is however not possible according to RME (DSP processing power limitations due to all the other audio settings that have been implemented). Therefore the volume control does
not fully reach what I would want for my definition of perfection, but
is still very good nonetheless. Listening very quietly is however still possible from the IEM output, even when using extremely sensitive in-ears such as my Campfire Audio Andromeda.
Accelerated volume control (recognises when it's turned quickly - the same goes for the remote control (fast-ish continuous clicking as well as holding)). Works very well - slow and moderate turns/inputs allow precise, fine adjustments, whereas turning the knob rather quickly changes the volume in bigger steps (this works very well now since one of the latest firmware releases (earlier firmwares activated the accelerated volume control too soon, already when the potentiometer was turned slowly, but now the recognition of volume control inputs is excellent and accidental accelerated volume changes are highly unlikely)).
Frequency Response and Output Impedance:
IEM Output (no Load):
IEM Output (no Load):
Perfectly flat, just like it should be.
IEM Output (Load: Ultimate Ears Triple.Fi 10):
Extremely minor deviation with my critical Triple.Fi 10 as load. The calculated output impedance is perfect 0.1 Ohms.
PHONES Output (no Load):
Perfectly flat, just like it should be.
PHONES Output (Load: Ultimate Ears Triple.Fi 10):
The calculated output impedance based on the deviation is less than 0.5 Ohms - excellent.
Hiss Performance:
Perfectly hiss-free from the IEM output, even when I'm using my extremely sensitive Campfire Audio Andromeda, Shure SE846 or Ostry KC06A. That's true perfection that only very few devices that also have a very low output impedance manage to achieve or come close to.
Almost perfect from the PHONES output, however just almost. Very mild, subtle, almost nonexistent hiss even using extremely sensitive in-ears. So not as perfect as the IEM output, but still (way) better than what most other devices on the market are capable of, and close to perfect even with extremely sensitive in-ears.
Subjective Sound Impressions:
Not really surprisingly, it sounds just as clean, transparent and neutral as a flawless audio device should sound.
Conclusion:
Objectively probably the best all-in-one DAC on the market for super sensitive in-ears, headphones and speakers alike - perfect output impedance; perfect hiss performance; otherwise excellent measurements as well; very good, near-perfect volume control; plenty of features.
Just excellent.