Four Hour Tube Amp Warm-Up

I’m becoming more open to the idea that sound quality could improve up to 4 hours, which seems to be around the amount of time for the big transformers & their potting to fully warm up. However, it is very difficult to separate any such sonic differences from psychoacoustic explanations (without 2 of the same amp), and I still posit that if an doesn’t sound good within 10 minutes of power up, something might be wrong or "off" with it.

4 hours -- wow. So, tube life is, in effect, one quarter of their expected life for good listening? That will sound like an argument for solid state to many.

@hilde45  As per above, I would never wait 4 hours to start enjoying the amp. And as for solid-state, there’s another thread floating where a very well regarded SS amp blew and took out the unlucky owner’s JBL speakers. I think tube amps are a lot more reliable than many audiophiles give credit to, and SS are not the infallible devices either, perhaps with even more potential for downstream damage (direct coupling!). A lot can go wrong with transistors; they’re mechanically robust but don’t take electrical trauma well - the reverse of tubes!!

I'll try to be more precise in my warm up time for this post. Much of the warm up time has to do with amp, tube and parts replacement. New tube components, or new tubes or parts in well burned in tube equipment never bloom in initial phases or hours of burn in. Over time, at somewhere between 50 and 100 hours blooming will often take more warm up time, this may be as much as 4 hours, as burn in progresses warm up time decreases until a consistent warm up time of aprox 1 hour at full burn in.

My 300b monoblocks are undergoing this  repeated progression at this very moment, recently replaced all coupling caps with Duelund Cast, getting up into 60 hour range and blooming is coming in starting around 3 hours and progressing from there. Between changing out tube components, parts and tubes for nearly thirty years now this is entirely common occurrence.

@mulveling "However, it is very difficult to separate any such sonic differences from psychoacoustic explanations"

This is the Achilles' heel for many discussions. Obviously, the OP knows his own mind best, and we have to stipulate to what he's hearing. That said, 4 hours is a very long time, certainly an outlier in terms of what others report and what the equipment should be able to do. (Imagine a car that took a full 60 seconds to reach 60 mph --- that would obviously indicate a problem or bad design.)

As for your comment about the fallibility of SS -- good point. Tangentially, I'll confess that my Pass XA25 takes about as long as my KT88 tube amp to sound decent, and it sounds great after it's been on a long, long time. 

bigtwin wrote: "I'm not aware any any manufacturer that suggests leaving equipment powered up 24/7?  I would think you are only shortening the eventual life span of things doing this?  Just asking."

When I bought my Pass Labs XP17 phonostage I called Pass and asked if it would be OK to leave it on 24/7.  I was told that it was designed to be left on all the time and that is why the only off/on switch is located on the back of the component.