I have an RCA blackplate 6L6GB, which is a great sounding tube. It ODs nicely in Champs and tweed Princetons. The "W" designation in tyour tubes stands for ruggedized. The 5881 was an industrial tube, also ruggedized. IIRC, they were used in mobile radios in the US military circa WWII. Those tubes had to be tough. I have a pair of reall 5881s pulled from a hifi amp and they sound glorious in my homebrew tweed Princetons.

Quote Originally Posted by sunvalleylaw
Good to know. I wondered what the tube designation meant. Your description of moving toward BF sound is accurate from what I have read. As I understand it, the brown amphs of the early 60s are in between the tweeds and BFs in terms of tone and headroom. It seems to have lots of warmth to my ear, and to me, that gives a bit more character than the squeaky clean BF sound. But that is based on models I have listened to and played through (Line 6 Gearbox models, etc.), not really experience with the real thing. It seems to have enough tweed in it to make it enjoyable to me.