Four Hour Tube Amp Warm-Up

Pretty much in agreement with the above, this with many tube, both push pull and SET over many years. I notice as the amps age magic time can lessen to around two hour mark, also depends how hard I run them, running them hard further lessens time. I do always give at least hour lower volume prior to kicking things up. I also use boutique caps over much of my system, the physically huge caps I run in speaker crossovers need the hard running time.

By far the most incredible listening session happened two days ago after the PL's had been accidentally left on for 7 hours. Technically, the Sophia EL 34 power tubes may not be "fully" broken in yet, but they have about a 100 hours on them of playing time.

I can agree that full transformer saturation may explain a lot. The solid state cd transport and DAC are of course kept on all the time. The Primaluna pre and power tube amps are not in the interest of tube life. If they didn't sound so good I would probably go back to a full solid state system.

Dozens of tube components later, the only ones I ever had concerns about a warm-up time longer than (say) 15 minutes were the hybrid electrostatic amps with lots of high-voltage transistor CCS on their outputs.

Never really experienced that with any pure tube components. They should sound really good very quickly. Unlike transistors, tubes need heat to operate at all, and they have filaments for that very purpose - which efficiently heat up so the tube operates at spec very quickly. Transistors are however affected by heat, and can take a relatively long time to reach their final stable operating temp - because heat sinking is used to pull heat out to keep them at a safe operating temp under maximum load conditions. There’s no such heat tug-of-war with tubes, so they get stable quick.

The only aspect of tube amps that has a slowly heat-accumulating element would be the transformers, and maybe silicon rectifiers and voltage regulators in the PSU. Though only large transformers should take hours to fully warm up. I don’t know if that significantly affects their performance - maybe. That could be the "4 hour warm-up" in your case.

My experience mirrors Tablejockey 

I always enjoyed the process of hearing things open up- I'd say 45 minutes is sufficient for the Lamm ML2 SETs and a couple or three sides of LP for the cartridge to really come into its own (after initial settle in which could vary depending on cartridge). My small vintage system running old Quad IIs with period glass (GEC KT 66s!) and restored Quad 57s is pretty much the same on warm up time. And you can clearly hear when these systems just bloom- everything opens up. 

I've been using various tube amps and preamps since the early '70s and can't say my experience decades ago is much different using then current ARC tube gear, but my sonic memory isn't that good.