I typically just leave the volume on the integrated amp (which has balanced input; Marantz doesn’t seem to have it) at about 9. It can be controlled from a remote but very ergonomically, so it is simpler to adjust volume from the (great) remote that now comes with the RME ADI-2 DAC FS. I sometimes also adjust balance, a control that my MF M6si does not have. Volume is changed in the digital domain so it’s perfect. Withe the remote you can also dim the display which is a great feature. This DAC is great with my beyerdynamic headphones and IEMs!
I don’t remember my settings for balanced vs RCA but can find out that discussion
https://forum.rme-audio.de/search.php?search_id=657718769
I found it: "I just changed line out reference level to +1dB, as XLR out adds 6dB, to achieve the recommended +7dB"
So for balanced, I use +1 dB out ref level (higher levels were leading to distortions). I don't use line out any more but the ref level was higher. It is important to get this right!
I don’t remember my settings for balanced vs RCA but can find out that discussion
https://forum.rme-audio.de/search.php?search_id=657718769
I found it: "I just changed line out reference level to +1dB, as XLR out adds 6dB, to achieve the recommended +7dB"
So for balanced, I use +1 dB out ref level (higher levels were leading to distortions). I don't use line out any more but the ref level was higher. It is important to get this right!