I've been using JJ tubes for years, I was convinced by all the positive reviews that they were the best, I was also skeptical of the unbranded "Preferred Series". Who makes them? Where do they come from? Took a chance and ordered the "Premium Package". What a revelation! These tubes are all that thetubestore claims they are and more, I couldn't be more pleased with the beautiful sounds emanating from my amp, as well as the complete absence of background "hiss" these tubes allow my amp to realize its full potential! Awesome!!!