Thanks Wyatt, I do see the use of a standby but it was always explained to me (by electronics "experts") that it was needed with tube amps that had solid state rectifiers to avoid sudden voltage surges (??) and damage to the tubes. It seemed that its secondary use was to power down temporarily when at a gig.
Nik and the other guy both make/design/sell tube amp kits and both say the standby switch isn't needed, but for different reasons! Some players and techies who write for magazines warn of dire problems if an amp is powered up without the standby switch in the "On" positions! Ditto for powering down - do it wrong and your head will explode!! Joking of course, but opinions seem to vary.