Thank you for the link above, showing the objective FFT 100kHz broad-spectrum noise data, showing that the Noise Harvesters don’t subtract much noise, and even adding a little of its own noise at 88kHz.
That said, however, I think they’re pretty cool as AC line noise detectors - I own five of them.
I’ve found that BITs are the ONLY way to go, and are especially effective when plugged into the AC duplex outlet of my P20, with a five-conductor “balanced” AC cable to power my front end components. Not surprisingly, the Noise Harvester does NOT blink at all, when plugged into my BITs, which is absolutely wonderful and reassuring that the BITs doing their job admirably.