If I turn it on and immediately put on an LP, the soundstage is flat and things are a little lifeless. But after three songs (12-15 mins) it transforms itself and I hear the midrange front and center with a beautiful bloom. After 30 minutes, subtle improvements. After 60 minutes, it stabilizes and I settle in for a glorious listening session.
The Zesto is the same way.
Plus, I have tubes in the REF10 power supply, controller and tubes in the two REF250's in the warm up.
When my tubes need replacing, I'll be applying for a second mortgage.
I drive a Hyundai because I need to save for tube replacements!
As Nelson pointed out, the detail at low volumes with the REF PH2SE is exceptional.