A question I suspect reveals a lot of ignorance...

Thanks to all.
Viridian, Herman & Atmasphere - seems like you all agree tube life in Class AB amp service is affected by volume level. Guess I'll look into buying some spare tubes!!

Dpac 996 - Don't know what ill effects cranking things up prior to full warm up might have. BUT I too hear an improvement after things have been running a while. Seems a common experience with tubes - but I also thought that with a solid state receiver I ran in the past - the sound opens up. After 1 hr for sure...but I think after a few hours, there is another step change. No quantitative data to back this up - just an overall impression.

Good listening to all.

Don't tubes draw the same amount of current at all times when they are biased correctly? Otherwise biasing would only matter when the amp is not playing.

Don't know the answer either, but would like to ask whether anyone knows whether or not it is ok to immediately play the amp after switching it on? I seem to recall reading somewhere that a tube amp should be allowed to warm up a few minutes before receiving a signal...

Don't tubes draw the same amount of current at all times when they are biased correctly?

No

whether or not it is ok to immediately play the amp after switching it on

It won't hurt it. It just won't sound right.

My experience with tube amps is that they tend to sound better after some warm up...same with ss amps. One of the things that I always wandered about when I was using tube amps was where in the life of the tube ( power tube) was I listening. I had an ARC and then a Melos and with the Melos, the power tubes would fail often; Sometimes in spectacular fashion. The quality of the tube was a major factor as far as the life and sound of the tube was concerned. With some of the Chinese tubes, the lifespan was maybe a few days or less! One of the issues I still have with tube amps is the heat they tend to throw off, however, after having lived with ss now for more than ten years, I personally am willing to add a tube amp for the difference in performance they provide. But, I still will use ss for my peace of mind.