12x7 tubes

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.

I have had good luck with military spec sylvania NOS tubes. Actually many companies made NOS military spec tubes for the US and they are just awesome. RCA, GE, Philips, Raytheon. They usually have JAN in the name (Joint Army Navy). Jasonbourne52 is correct on the money. I have had really good sound from JAN 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.