Hi!
You can read those threads:
https://forum.rme-audio.de/viewtopic.php?id=29029
https://forum.rme-audio.de/viewtopic.php?id=29388

In a nutshell: if you don't need analog input, don't bother with a useless preamp between your power amp and the ADI-2 DAC; this machine is a very good and transparent preamp: smooth digital volume control, dynamic loudness, adjustable B/T, EQ corrections, 4 hardware levels automaticaly switchable (Auto Vol Ref), remote etc.

Hi @ashmpatel - there are two quite differing camps on this forum about whether a preamp is necessary in the audio chain from a sound quality perspective.  Some say that if you don’t need analogue inputs, then a preamp just adds unnecessary boxes and distortion.  Others say that the preamp can improve subjective sound quality.  The arguments can get quite heated, so my advice would be to try both suggestions above and see which works for you.

My experience was that I started using a preamp, then started switching back and forth undecided on which sound I preferred, then realised I liked the cleaner more detailed sound without the preamp.

Though your experience might be different.  By all means try the EQ, treble and bass adjustment with a preamp in the chain as what matters most is what sounds best to you.  The the great thing about the RME DAC is that you can adjust to your heart’s content, knowing that you’re using a very high precision instrument.

If you set "Auto Ref Level" to ON (its a switch ON or OFF), then the Ref level (+19 dBu, +13 dBu, +7 dBu, +1 dBu)
if the analog output is being chosen automatically by the DAC depening on your Volume setting to achieve optimum SNR.