FWIW, I used an AI 2C for many years and found the Svetlana 6n1p to be the smoothest (least harsh) tube type of any that I tried. AI warns against using the 6n1p for performance reasons, however, for me, it was consistently the preferred choice in my system. They're relatively cheap and so might be worth a shot... (Note that this tube is listed as a recommended choice in "Joe's Tube Lore" referenced in a post above..).
Just got Audible Illusions L1, but it sound harsh
I just got a Audible Illusions L1 preamp to replace my Rotel RC 1070. I can hear it is much more detail, it sounds more forward and bigger sound stage. But I also found it too harsh. Especially in vocal, the "s" sound is very loud and quite alloying. I don't have it in my RC 1070, but at the same time, it doesn't sound as musical. It is just like sing behind a curtain. I don't hear that detail, but also, those annoying "s" sound is "filter" out. Is it a characteristic of this preamp? Is there any thing I can do? I am using a Rotel RB 1080 amp. Should I try another preamp? Or try another amp?