I have always said that I believe a linear power supply could improve audio. This has not changed. Back in the 1080p days I was skeptical it would improve video. Now for 4k, while still somewhat skeptical about video, I believe there is the potential a better power supply could help video when the underlying display technology is analog (DiLA, LCOS, but not DLP). The improvement might not even be visible at viewing distance though. That is why I add it may help. I do not want to discount it completely, and there may be a visible at viewing distance improvement. People need to test for themselves in their system.Interesting especially (to me) the unexpected jrp positive response about power supplies.
Is there such a thing as a power supply noise generator? ...
There are noise injectors, but I think the time spent would not yield much. Choose a linear power supply. Then compare audio and video using the Radiance Pro digital power brick, versus the linear power supply, and judge for yourself. I can be pretty certain some will say "no difference" and some will say "there is a difference." I believe the people who say they hear/see a difference, and I believe the people who say they don't. It is after all system and listener/viewer dependent.