Sorry, the RME ADI-2 FS DAC

https://www.rme-usa.com/adi-2-dac.html

Thanks! I also found the ref level setting for my line output (to my tube amp) and set that to +13db.

Thanks!

Really? I found it quickly browsing through the 1st chapters (ch 12.3, p. 23).

Regarding search at tip. It can always be the case that something is not written in the way as you might expect.
Then try with substrings like "power" which should be more likely to be found.
Especially in this case, as you might remember that this is a key feature of ADI-2 DAC and Pro, so information must be there.

Side note: the term/mode "Hi-Power" (as it is called in the menu) is explained / introduced in ch 8.1 about "Extreme Power Headphone Outputs".

"Hi-Power
OFF, ON. Default: OFF. Reference level for 0 dBFS is +7
dBu at the output. With Hi-Power "ON" reference level is 15 dB higher, +22 dBu."

To avoid a misconception for those expecting sound improvements from switching to Hi-Power:

ADI-2‘s headphone amp itself always works on full power.
The Hi-/Lo-Power switch ony changes the analog gain in-between DAC and amp.

This means if you switch to “Hi-“ and don’t use the extra power/level available, you just have to turn down the digital signal BEFORE the DA-chip, and as a result get a lesser SNR / Signal to Noise Ratio.

There’s no “rule” like “Planars” need Hi, and “Dynamics” need Lo, or alike.
It depends on a multitude of factors that might vary a lot.

So, for best results, activate “Auto Ref Level” and let ADI-2 do the switching in case “Hi” is needed.

Only if your ‘phones can break with Hi-Power, like the ones from Focal, stay away from “Auto Ref Level” and set Lo-Power manually.