I am happy to weigh in on this lengthy thread. I swapped the Red for the fuse in my tube preamp and listened to it for a week. Then I swapped back the standard fuse, which turned out to be a Hifi Tuning fuse. Then I did an A/B comparison for a while with familiar music. To my aging ears, there was no difference in sound -- zero, zip, nada. So, for the price of a couple of stamps, I sent it back for a refund. I demo’d SR’s room dots (the little AL plugs arrayed around the room) and had the same experience. Still, they give 100% refund so you may find some merit in their products. I have a bunch of bottle caps from the dozens of Harp beers consumed at my home on St. Paddy’s day and I am gonna glue them all over the wall to simulate the effect of SR’s dots. I am always in search of a cheap tweak, but the SR products so far have not produced any improvement. Cheers.