I've been using a recently produced Theorem for a few hours and the hiss is unbearable. It doesn't matter if it is a LCD-3, Shure SE846, or a NAD Viso HP-50. I tried another Theorem from a friend with the same results. We're both returning our products. I just don't get it. I noticed a little bit of hiss with a Cypher Labs CLAS -db/Duet combo and it was't much of an issue. This hiss is ridiculous - even worse than the ALO MK3. Compared to the non-existent noise floors of other companies, how does any company put out a product that ruins any music with silent parts? A non-existent noise floor should be a minimum standard that amp manufacturers should be held to. I understand that this is a personal preference, but all the rest of the sound seems irrelevant when I feel like there is a dang mosquito stuck in my earpad.