12x7 tubes

Stellar Quality

Space and military applications required electronics that could operate reliably in extreme environments of high altitude, high acceleration/vibration and even space, where high levels of radiation are present. Incidentally, one of the reasons Russia continued to manufacture tubes was because these thermionic devices are immune to an electromagnetic pulse (EMP), the gamma ray burst that an atomic bomb releases upon exploding—Russian MIG jet fighters were equipped with tube circuitry in their radar systems so that an EMP would not interfere with onboard navigation systems.

Tube reliability was a real and ongoing concern for the US military. You may have seen the initials ‘JAN’ stamped on Philips N.O.S. tubes, which is an acronym for ‘Joint Army Navy’. These are ruggedised tubes manufactured for the military. During world War II the American military initiated a ‘ruggedisation’ program with aim of improving tube reliability in the field. For example, there was concern that delicate electronic comms equipment thrown around in the back of a jeep hurtling along a rock strewn dirt track might not fare too well. To remedy this perceived problem with reliability tubes were designed with shorter, stockier anodes, additional or thicker support micas and a very complex and elaborate tube numbering system evolved along with the numerous revisions of tubes [Getting the Most Out of Vacuum Tubes by Robert B. Tomer pages 72-75]. Reliability of electronics and tubes in military and space applications was of paramount importance.

True some tubes were designed from the ground up for military application, but most were not and were simply tested for shock and vibration by the factory for the military. The internals of these tubes were no different than the tubes released to the civilian market. Further, in most cases, audio considerations didnt exist for military applications, perhaps in some cases noise could be an issue but even this may be a stretch. Now if certain military design concerns necessitated change that influenced the overall tube market back in the day I cant comment to this. To assume that a JAN tube or more importantly a JAN designation indicates a better sounding tube would be a mistake.

audition__audio,

I agree with assuming that military spec product even matters in audio for the intended purpose that the product was made. You would better off reading and understanding say a JAN tube mil. specification before assuming that it would make the best for audio.

 BTW, are talking about 12AX7, AND NOT '12X7' CORRECT?

When I post information, it is about my experience with a product. I don't make blanket statements about what is good or bad. From the tubes I purchased and money I spent I found GE, Phillips and Sylvania NOS Jan tubes to sound very good. Not sure why my opinion would mot be as valid as the next. So my advice, in addition to my experience is that be careful what a salesperson tells you, often times they are very biased and arrogant with their assertions.

@boomerbillone 

NOS Telefunkens sound best, but are pricy. Try anything else to get your amp "on the air."

I like them, a lot. In terms of "pricey", I found four smooth plate that were Dynaco stamped, which costs much less than factory Telefunken stamped tubes. Got four for $380. No regrets for these great tubes.

As far as new, a similar sound signature as the Tele's,  but more grainy and not as smooth, is the Gold Lion gold pin tubes. You can get them for about $40 per.