I suspect that the higher filament current of the EML 300B-XLS (1.5 amps per the datasheet at their website), compared to the 1.2 amp spec of the original Western Electric tube (to which the KR tube conforms) is a factor in the very long reported lifespans of the EML XLS that Charles referred to. The higher current draw will result in more voltage drop in the power transformer's filament winding and/or other power supply circuitry, resulting in less voltage being applied to the filament, compared to a 1.2 amp tube in the same application. The reduction in filament voltage would presumably result in greater longevity, and perhaps also contribute to the sonic character of the tube.
In any event, though, as you (Jkull) indicated you should verify that the amp can supply 1.5 amps to the tube without issue, if you want to consider the EML XLS.
Good luck. Regards,
-- Al
In any event, though, as you (Jkull) indicated you should verify that the amp can supply 1.5 amps to the tube without issue, if you want to consider the EML XLS.
Good luck. Regards,
-- Al