Hello new here, so sorry if this is novice territory. I am trying to find a way to more easily control headphone mixes for multiple people while recording, and be able to control different volumes for each headphone. I don't always want to be listening at the same level as the person I am recording. RME comes with the 2 headphone outputs that can't be controlled separately (from what I've heard), so I bought a Presonus hp4 Headphone amp to use. I plugged in a balanced 1/4" TRS into the headphone jack on the RME that goes to a y-split 1/4" TRS into the Presonus, since on the Presonus you have to plug in a left and right, not just one 1/4" TRS like on the Mackie hm-4 or Behringer HA-400. I can barely hear any volume coming from the headphones plugged into the Presonus hp4. I'm guessing it's a cable issue, or the headphone amp in the RME can't handle the boost to the Presonus? I hooked up the Presonus to the 2 monitor outputs (XLR to 1/4 TRS) on the RME and it sounds amazing, but I want to be able to use that for my monitors, while I have the headphone amp going through the headphones output, so I can control up to 4 headphone mixes all separately.

Just wondering if anyone knows if the Presonus hp4 is compatible or not, or if I should try for a different headphone amp that would work while plugged into the RME headphone jack. Also wondering if I'm using the wrong cables.

Adam