Ten minutes warm up time. Although I have some routines like getting up going downstairs, turning on my equipment, brushing teeth, get coffee, sit down and listen, so warm up time happens without a hassle... but the gear sounds great immediately, but does improve over ten or fifteen minutes.
I would say if given the choice of either Luxman or ARC, which ever you choose, it would be highly advantageous to go all that brand. I am and have been completely in synch with where Audio Research is going over the last 40 years, it has just taken me a long time to realize it, afford it, and for them to introduce a really reliable, auto biassing tube amp. I don’t want to fiddle.