So I am the OP. I have SE535s that I had been using for running because, besides sounding really good, the particular foam inserts stayed in my ears. Tonight I tried the DAC for the first time. I registered for Tidal for the 30 day free trial. I am sure I'm using HiFi settings because I signed up for that trial and changed all my settings to HiFi within the app. I downloaded a blues album (Move by Lucky Peterson) and plugged in my SE535s. Turned on the DAC. Now, I am 50 and have a slight to moderate case of tinnitus, and while the sound is fantastic, I can hear no difference between the tracks with the DAC turned on or off and, for that matter, the same album on Spotify sounds the same (on the extreme setting). I guess one parameter I'm using is background hiss. Everything sounds identical for background hiss. I was expecting the hiss to be eliminated. Am I doing something wrong? HiFi audio is new to me.