The LS2B is not known for warmth and musicality in the first place.
I'll amend my original response, with some agreement with the above statement. I always found the LS2B to be rather cool and detached - and yearned to find warmth there as well. Though the Mullard is a fine tube, and did impart some sense of "warmth", it was only a bandaid - I actually preferred the pre with the more linear/neutral Siemens CCa tube for greater resolution I believe, though thought the Mullard was very nice as well (consistently my second choice). I believe I had the LS2B for a year or two, having tried pairing it with several different amps, and it's one of those components I really don't miss much or remember with much fondness, especially having a whole lot of experience with much better preamps. I used to keep mine on 24/7 per the suggestion by Rrog. I really can't recall it making a night and day difference, but then... it was a long time ago. BTW, I would certainly not consider the tubes being discussed as inexpensive. The Euro 9-pin varietals that are the cream of the crop of E88CC's range from $130 up to the $300+ range per tube from a reputable seller. Fortunately you only need one. Ultimately I'd suggest that if you are highly unsatisfied with the foundational sound signature of that preamp, which I would classify as cool and analytical, sell it and buy something that may suit your tastes better as the improvements, at least in my experience, are not enough to change the basic signature of the pre.
