Could I add a question? Are there any benefits to add the pre90 to use its analogue volume control?

I agree, but the quality loss is not that high.

I would rather make it dependent on whether there are big level mismatches in your setup or not.

In other words, whether the default volume setting of the ADI-2 DAC/Pro (which is around -30 and that could become active accidentally when selecting another preset) is still tolerable or already much too loud and could perhaps even damage hearing or equipment.

With a passive volume control, you definitely have an additional security that a certain maximum volume is not exceeded.

Of course, you can and should work on your setup and solve the level mismatches by using attenuators, see this very informative posting from Matthias Carstens: https://forum.rme-audio.de/viewtopic.php?id=25399

Makes sense, but this particular goal could be achieved by using much simpler and much cheaper solutions. No need to have a sort of passive attenuator with 0.5 dB granularity just to fix a mismatch of signal levels

I use a pair of Shure A15AS attenuators set to -25dB between my Pro 2/4 and my active ATC monitors and it works great. I like to listen around 75-80dB SPL in the room and usually have the Pro 2/4 set anywhere from -30 to -6 depending on the source material. No need for a sperate monitor controller, preamp or other analogue volume control.

Ah, ok.

Thank you so much for posting this. I have an ADI-2 DAC FS. i also have normal age-related hearing loss and therefore I'm always looking for ways to get more (music) detail, bass, etc., from my system at lower volume levels. I generally listen to music between 65-70 dB. By trying scenario 1, I'm now getting a lot more music detail and punch at lower volumes as opposed to running the ADI-2 at negative values. I use an SPL meter for matching both scenarios to make sure that I'm not simply hearing louder music with the RME volume set to 0.

I was already super-impressed with this DAC, but am now even more so. Amazing.

Thanks. I'll give these settings a try! Right now I've got bass gain set to +2 and treble gain to +4. I'm actually letting my amp do most of the EQ function because it seems to impact the music more than the ADI-2. It's also a 5-band EQ. (McIntosh MA352).

Unlike Bass and Treble gain, the loudness range is 20dB and fix (in the manual it's explained why).

So, if you set Low Vol Ref …

Case a) … to -30, then the loudness starts with -10.5 and has its maximum Bass/Treble Gain at -30

Volume (-)            0----5---10---15---20---25---30
                                            |--------20dB fix-----|
Loudn.-Gain B/T                    min                    max
                                            -0.5                     -30
Low Vol Ref                                                     -30

Case b) … to -20, then the loudness starts with -0.5 and has its maximum Bass/Treble Gain at -20

Volume (-)            0----5---10---15---20---25---30
                             |--------20dB fix-----|
Loudn.-Gain B/T    min                    max
                            -0.5                     -20
Low Vol Ref                                     -20

As you use the volume starting with 0 and wanted to get loudness quicker starting at -0.5 if I remember right,
the Low Vol Ref had to be reconfigured to -20 so that loudness kicks in at -0.5 and has its maximum at -20 (Case b)

See manual ch 8.5, it's all nicely documented there. Tip: use the search function of your PDF viewer.

https://www.rme-audio.de/downloads/adi2dacr_d.pdf
https://www.rme-audio.de/downloads/adi2dacr_e.pdf

8.5 Loudness

Another legacy of HiFi amplifiers: there has not been a single one missing a feature called Loudness. It tries to address the changes in frequency-dependent hearing sensitivity over different volume levels. If one listens to music loud, then drops the level by at least 20 dB, sound loses punch and glitter. HiFi amps tried to fight this effect by adding more bass and treble the lower the volume was set. Unfortunately that never worked as intended, and just became an additional bass/treble booster. Reason: the manufacturer of the HiFi amp could not know what volume any position of the volume knob equals at the customer’s home. Room size, room dampening and efficiency of the used speakers are all unknown.

But the effect of loss in perceived sound exists (read about the Fletcher-Munson curves), and can be easily reproduced with any serious gear by comparing normal volume and DIM state (usually -20 dB). The ADI-2 DAC offers Loudness for the analog stereo outputs, and probably is the first time that Loudness works as intended. The user can decide how much maximum gain in Bass and Treble should occur at lower volume settings. The user also sets the Low Vol Reference, where maximum gain is achieved. After extensive tests a 20 dB range has been defined as range for maximum gain to no gain while increasing volume. That seemed to be the perfect definition of the range that needs to be addressed by Loudness.

Here is an example on how it works: the user’s typical lowest level listening volume is at -35 dB at the unit. This value is now set by the user as Low Vol Ref in the Loudness menu. Then Bass and Treble Gain can be set between 0 and +10 dB. Default is +7 dB for both. Increasing the volume by turning the Volume knob causes the gain in Bass and Treble to be lowered smoothly over a range of 20 dB. So when Volume is set to -15 dB, the music is not only quite loud, but Loudness’ Bass and Treble are then at 0 dB gain. See chapter 31.6 for graphs.

No matter how sensitive the connected phones or speakers are, no matter how much increase in Bass and Treble are desired – with the ADI-2 DAC one can finally adjust it to meet the personal hearing and taste. Loudness finally works as it should have worked from the start - another unique feature in the ADI-2 DAC.

Note: Loudness works best in Auto Ref Level mode due to the seamless dBr scale of the volume control. Without Auto Ref Level active, manually changing the Ref Level will change the volume without changing the VOLume value (dB). As Loudness is referenced to a 'Low Vol Ref' setting it then might no longer work as intended, and needs the Low Vol Ref value to be adjusted.

KaiS made you proposals, I only reacted to your questions to explain Loudness.

Its your choice how you configure dynamic loudness.
Wondering why you ask again.

I copy/pasted you from the manual and there is the answer to your last question.

"Here is an example on how it works: the user’s typical lowest level listening volume is at -35 dB
at the unit. This value is now set by the user as Low Vol Ref in the Loudness menu."

My proposal aims for your special case: needing a touch more extension at the frequency extremes.
This is to counteract subjective losses due to home-compatible listening level being lower than producer‘s.

I kind of re-target the Loudness function, as it has perfectly parameterized preset EQ settings, instead of using it’s original function like described in the manual.

In cookbook manner, try the settings I purposely proposed.
Use ADI-2’s volume just to dose the amount of this spice.

Lower ADI-2 volume setting = more spice.
0 dB volume = original unchanged flavor.
If -5 dB volume gives too much of it, try -3 dB e.g.
Final listening level is still set with your analog amp then.

As you need only minor volume changes, ADI-2’s full dynamic range advantage stays intact, preserving the sound that you said you liked.