Tube equipment use in high altitude?

Tubes were used in the radios of World War II aircraft at flight levels of 25 thousand feet or more - the same types now sold as NOS. Also, these were the VT or military spec tubes which were built for the altitudes, vibration and temperature extremes of unpressurized flight. I don't see a problem with good 'ol USA NOS tubes or even Russian military. Chinese tubes tubes, though, I wouldn't trust for many other reasons.

That's a very good point! I had completely forgotten about that aspect of tube history. Thanks.

Like many others, I've used tube equipment here in Santa Fe, New Mexico (7000 ft. elevation) with no problems. You're talking about almost another mile...to test it out, I'd have to haul my amp up to the top of Santa Fe Baldy, but there's no electricity up there (except lightning).

I have heard that amps are effectively less powerful with increasing altitude, or maybe it's that speakers are less efficient. Anybody else care to comment on this? I've had no problems here, although I do admit to fantasizing about living on the coast one day and hearing my system rock out like never before :)

Don't forget that tubes (Red Banks brand) were also used for the guidance systems of earlier American ICBM's (guided missiles). These tubes could withstand a force of over 30 G's that was generated at lift-off, and cruised on a sub-orbital flight path (essentially NO ATMOSPHERIC PRESSURE!). Jfacker, I would think that speakers would be less efficient (not the amps) due to decreased air pressure (density) at higher altitudes. Living on the coast would expose your stereo equipment to corrosive salt air, and large humidity fluctuations, not the best environment for a stereo rig. I have heard that the only potential high altitude operational problems are confined to plasma TV's used above 6000 feet.

Did the tubed ICBM's sound more mellow than the solid state versions on detonation? (sorry)

Gs: The "tubed" ICBM's don't sound quite as "shrill" sounding as they whistle by you... : ) Sean
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i live at over 8000' no problem with the tube equipment