Why no heated gear?

Herman, thanks for helping me to win a bet with myself. When I wrote:

So why can't we just heat the tube with an external heat source like a heat gun or a heated blanket? Because "tubes" are vacuum tubes - the glass envelope encases the internal elements in a vacuum. No gas (atmosphere), no heat transfer can occur from OUTSIDE the envelope. See what you can learn when you don't sleep through High School physics class?

I just knew that you were going to reply the way that you did. OK, you caught me. I am guilty of a gross oversimplification.

The fact is that the glass heats up when a tube is powered because of radiant heat. But it's an inefficient process, and radiant heating from a high temperature source in close proximity is a very different process than "warming" from a low temperature source from several inches away. Do you possibly believe that you can pre-heat a tube to anywhere remotely close to operating temperature? Actually, that is done (sort of) for certain types of specialized lab gear and of course cold cathode tubes, which operate at a much lower temperature. But it wastes a lot of energy and can't be done except in controlled conditions.

And regarding your last statement that there is no such thing as heat potential in a tube. Really? So you believe that the anode and cathode in a typical vacuum tube are EXACTLY the same temperature? Planck's Constant indicates otherwise. So between your opinion and Max Planck, I'll take Max.

"The entire tube, inside and out, will eventually reach the same temp whether heated from within or from outside."

From that unimpeachable source, Wikipedia:

"Vacuum tubes require a large temperature difference between the hot cathode and the cold anode. Because of this, vacuum tubes are inherently power-inefficient; enclosing the tube within a heat-retaining envelope of insulation would allow the entire tube to reach the same temperature, resulting in electron emission from the anode that would counter the normal one-way current. Because the tube requires a vacuum to operate, convection cooling of the anode is not generally possible unless the anode forms a part of the vacuum envelope (in which case the cooling is by conduction through the anode material and then convection outside the vacuum envelope). Thus anode cooling occurs in most tubes through black-body radiation and conduction of heat to the outer glass envelope via the anode mounting frame. Cold cathode tubes do not rely on thermionic emission at the cathode and usually have some form of gas discharge as the operating principle; such tubes are used for lighting (neon lights and neon glow lamps) or as voltage regulators."

Do you possibly believe that you can pre-heat a tube to anywhere remotely close to operating temperature?

uh, did I ever say that?

And regarding your last statement that there is no such thing as heat potential in a tube. Really?

Despite referencing several textbooks as well as the web I find no mention of the phrase "heat potential" when it comes to vacuum tubes.. I make no apologies if I misinterpreted what you meant when you used unconventional terminology.

So you believe that the anode and cathode in a typical vacuum tube are EXACTLY the same temperature?

uh, did I ever say that?

Granted, the cathode is generally heated to increase electron emission. That in no way negates the fact that keeping the tube warm when it is not in use will decrease warm up time.

You all can ignore what the original poster asked and try to nit pick responses, but the fact remains... if it starts out at a warmer temperature it will reach it's operating temperature more quickly. That is crux of the debate, double speak and patting yourself on the back for clever responses "I just knew that you were going to reply the way that you did" doesn't preclude the fact that any of you who dismissed the reality that preheating the equipment has a positive effect were wrong.

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Drill a hole and use a block heater - this is especially beneficial with diesel amplifiers.

"decrease warm up time" Well are we taking "How long a pre/amp take to sound it's BEST?" or how long it takes to be at operating temperature?
"I" thought we were taking about some slick way (pre heating with external heat) of making the waiting period (til the pre/amp whatever) for optimum sound (which is NOT just until the damn thing is warm). Now my prior amp (Forte 4a) took at LEAST an hour of being on to sound 'better' and nearly a whole day to sound great. Now hat amp was fully 'warmed up' in twenty minutes (far into class"A" operation) but no way did it sound great until it was on a whole day!!!
So i am sort of confused about some saying yeaah, external heat caould do it... no way IMO. Yes it could be 'warmed up' and 'at optimum operating temp' but NOT optimum sound quality from a external heat source.
Anybody care to clarify better?