Cryogenic treatments - an experiment.

[Cathode_Ray]

For the benefit of Cathode_Ray - chilling does not make metals hard - it does make them brittle and less malleable - .

Re Pyrex: I stand erected. But in tempering of metals it indeed is a process of heating and controlled cooling - and brittle will equate to hard... And stress relief(something I could use a bit of @ the moment) can be accomplished by extreme cooling followed by graduale return to ambien, uh I mean ambience...
Just thinking outside the box - I'll get back in now.

[JKB]

What about testing the electronic properties of the tube pre and post chilling? It would be interesting to see if there is any measureable difference.

I'm a firm believer in "tune with your ear, not with a scope". However, I'm pretty sure I wouldn't be able to tell the difference two tubes that measured close, but different. That being the case, I'm certain I wouldn't notice a pre-post difference if there was no measureble physical change in the treated tube.

Of course, any audiophile will tell you sound is not governed by physics.