Distortions in this test are simulated by creating a
mathematical model of real speaker. This "hiss" is
part of simulated distortions. I would take your point if it's some artifact of real speaker recording, but it's not. It's actual
part of the test and I even think it's correlated with signal (but it's too subtle so I'm not 100% sure)
. Also interesting thing is nobody mention this particular distortion in the thread. Seems like nobody noticed it. I do and it's "invalidates my results". Interesting logic. Sounds like I'm cheating the test or something.
ES9023+O2 amp+dt990. But I can hear it even with my cheap equalized in-ears. I think you can hear it too, just carefully pay attention to first seconds of the track.