I’ll look into that line noise eliminator. Some audio equipment vendors also have devices purported to do this (Shunyata has their inexpensive Venom Defender which simply plugs into a spare socket on the same circuit as your audio gear).
Regarding the Audiosciencereview video, he also tested bands within the audible range and presented it as proof that the PS Audio PP-12 actually makes the sound worse. I read another report he did “proving” that Audioquest’s Niagara 1200 was utterly useless, and even as a surge protector was not well-designed.
Regarding his theory that our brains trick us into hearing the improvements, well my initial finding of the Niagara 5000 with the NRG-1000 cable sounding worse in the mids and uppers hopefully suggests that I lean at least to a more objective assessment of the sound. I honestly don’t have any strong faith that the Niagara or Torus conditioners when paired with a high end Dragon power cord will do anything for me. I’ll admit I WANT them to work though!
Another example - I just recently realized that my Audioquest Diamond USB cable between my Innuos streamer and my InnuOS reclocker sounds inferior to the generic cable that came with the reclocker, with the generic cable sounding a tad more open and detailed! Note that without the reclocker and plugging the USB directly into the DAC, this is not the case and the AQ USB cable wins. But just goes to show that ears can seem to be objective in some cases too.