The XLR inputs of the Lamms are for convenience - to save an owner the expense of new IC's - and not for balanced operation. By definition, single-ended-triode (SET) operation involves amplifying the entire signal with only one output device. A balanced circuit cannot be built this way, but I guess one can always install a shorted XLR input. Why don't most SET's have XLR inputs? Maybe it has to do with the tradition or purist angle.
