Good post - although I always thought the assumption had to do with the ruggedness of the tube, not the "sound". Do you think there is, or is not, an actual difference in in the ruggedness of tubes when they carry this designation in their number codes. (European or USA)
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I'll ask my mom and try to post later. She was a utility operator in a Sylvania tube plant in Pennsylvania from 1943 to 1957. As a utility operator she could do all the production jobs along the various assembly lines; and was responsible for training new people.
I can remember her saying they use to throw away perfectly good tubes because of cosmetic defects. No factory outlet stores in those days, Ha! A shame, there would be bigger supply today if they did not toss those tubes.
My understanding is that sometimes (not always)there is a difference in military tubes. If the original use is to use them in Mig fighters or something that is understandable. Sometime it is just quality control too. Generalizations are probably hard to make in this area. I'd be interested in hearing opinions on this point.
There are some good crossreferences such as the bottom of this page. I have a more complete site but can't find it at the monment. I'll post it if I find it.
Here is list that might help newbies too. The first few explain tube numbering which is a bit of a mystery when you start out. The second set are online sources for tube data. The first three (Duncan, Frank's and Triode Electronics) will usually have the info needed.
P.S. Hey Fletch. Nice posts for newbies but you sure use a lot of commas when you write.
Tube Numbering explained:
*) Åkes Tube Numbering: http://w1.871.telia.com/~u87127076/tabeller/index.htm
*) Tube Numbering Systems (Franks site) http://home.wxs.nl/~frank.philipse/frank/tubnum.html
*) Philip, Valvo & Mullard Valve Coding: http://www.cs.helsinki.fi/u/oheinone/valves/pvm-coding.html
*) Tube Numbering (MachMats Site): http://www.machmat.com/info/index.htm
*) Russian encoding system: http://www.arrakis.es/~igapop/russianotes.htm
*) Coding systems: http://www.arrakis.es/~igapop/referenc.htm
*) Phillips factory and tube codes: http://www.triodeel.com/images/philipstubecodes.pdf [Note that all Philips subsidiary companies (Mullard, Valvo, etc) and all factories that made tubes under Philips license used these codes (Ei, Toshiba, Siemens, etc) so it's not limited to European Philips tubes.]
1) Duncan Amps: http://www.duncanamps.co.uk/cgi-bin/tdsl3.exe/searchform
2) Franks Tube Data Page http://frank.nostalgiaair.org/index.html
3) Triode Electronics Tube Data Sheets: www.triodeel.com/tubedata.htm
4) Radau5s tube data sheets: http://www.radau5.ch/valves.html
5) Tubebuilder Tube Data: http://www.tubebuilder.com/tubedata.html
6) Vacuum Tube Valley: http://www.vacuumtube.com/FAQ.htm.
7) Svetlana, Tube Dictionary: http://www.svetlana.com/docs/dictionary.html
8) Audiomatica, Tube Directory: http://www.mclink.it/com/audiomatica/tubes/home.htm
9) National Valve Museums list of Equivalents: http://www.valve-museum.org/
10) 4Tubes. http://www.4tubes.com
11) Tube Collectors Association: http://www.tubecollectors.org/
12) Mach-Mat: http://www.machmat.com/sheet/index.htm
13) Kytelabs Tube infobase: http://www.qsl.net/dl7avf/roehren/roehren.html#TOC
14) An Intro to NOS tubes: http://www.soundstage.com/tubeor/tube.htm
15) Western Electric Archives: http://www.westernelectric.com/spec_sheets/we_spec_sheets.htm
16) Tom Jennings: http://www.wps.com/archives/tube-datasheets/index.html
17) Åkes TubeData: http://www.tubedata.com/
18) Magic Sound of Tubes (NOS): great pictures of NOS tubes. http://spazioinwind.libero.it/themagicsound/index.htm
19) Bills (NJ7P) Database: http://hereford.ampr.org/cgi-bin/tube?index=1
Newbie In some contracts, the specs for the tube, accounted for this. The tube, then, had a special construction(such as stabilizing rods, extra mica etc) This is when the tube, was different, and it had a different designation usually. But it only takes to look at a tube, and see the same internal construction, to know that there are no differences.
said above by Fletch >>>"But it only takes to look at a tube, and see the same internal construction, to know that there are no differences>"
Can you really do this????
If you can just look at a tube and do a visual inspection and see there is no difference then why go to the trouble of an electronic tube tester and matching?
There can be small differences in tubes of the same type and even the same run. This is just part of what they are and the tolerances involved and the production process. My understanding is that some tubes used in some critical military applications (Mig fighters etc...) were subject to much higher testing and Q control. I was also told that one reason that some old tubes are so good is that they threw so many away in the QC testing. Making tubes was apparently a process where a good portion of the runs went straight into the bins. This makes a certain amount of sense.
To the extent it is true I cannot say.
It may also be true that for some/many audio applications it may not make a big difference.
One of the dirty little secrets of tube use in audio gear is that one of the primary, make that the primary, consideration is audible noise.NOS manufacturer grading of tubes generally has nothing to do with noise. Likewise, the conventional testers that we use - I have both a Hickock 752 and a TV-7DU - check for filament, transconductance and/or emission. I don't really think that any of these parameters is going to say anything about noise. All we can really do is tell if a tube is outside of its operating specs or match tubes. Without listening, we can say that a tube is bad, but probably not how quiet it is in an audio circuit.
I can't understand why in this day and age there isn't a manufacturer of new tubes that can manufacture tubes that the audiophile community would want. With the ridiculous amounts of money we are willing to spend to get every last note out of our systems you think it would be a gold mine for some manufacturer.
said above by Hiwaves>>> "The owner had JAN tubes recently installed. The amps sounded OK, but when i replaced the tubes with Amperex tubes, the amps sound incredible, they just SING !!!
So much for the "sound quality" of JAN tubes."
I don't know what the sound quality of JAN tubes is, or if there is one such thing, but I do not agree that you can reach that conclusion from listening to one set of tubes in one circuit.
If tubes are anything like semiconductors (which I have 20 years experience with) the "differences" have to do with testing and traceability. Military semiconductors come off the same line as the standard devices do, but are subjected to a specified barrage of tests. Commonly referred to as "shake and bake" the military testing weeds out devices that may fail early on. The other significant difference is the paperwork that follows military devices through the factory and test floor, keeping a log of the measured specs as the part goes through the cycle. The parts that pass the military testing are sold under different part numbers and sell for a considerable mark up, anywhere from 10x to 40x the standard device pricing. Just to make things more confusing there are several levels of military screening: 883C, JAN 38510, and Level S (space level, for aircraft and space applications).
Bottom line is they come from the same production line as the chip sitting in your coffeemaker but are tested to insure longevity and consistent quality. Is it worth the premium? They are more rugged so they will last longer, other than that, no.
I honestly have never thought that certain tubes sounded better than others, solely because they were the military versions. There are just some types of tubes where the military versions just happen to sound the better. Others do not.
I was never aware of there even being a myth that the military tubes were automatically better. Makes me feel like some folks went for a sales pitch from someone selling those tubes.
I've always know those Amperex tubes were one of the best of those types. I never thought to considered whether they were military or not. It really did/does not matter to me.
The military tubes are just more durable. This is true of all things, even the military vs consumer model of the Hummer vehicle.
I don't know why or where this "myth" originated, but there are instances where, at least from my experience, the military version of a tube far outclassed the civilian variant: the Sylvania 6SN7 JAN CHS VT-231 and the RCA JAN 2A3 grey plates.
From what I understand, JAN tubes are manufactured to a military specification - not necessarily for the military. One of the most important parameters these tubes must meet is resistance to failure in high vibration environments and manufacture to tighter tolerances. For an audio application, this could mean a less microphonic tube. Not only that, but the mil-spec also dictated how they're packaged, shipped and stored - which means that the tubes found today probably had a better chance of surviving long term storage. Are they all better? Can't really make that blanket statement - because many of the commercial RCA/Sylvania/Ken-Rad/Philco/National tubes already met Mil-specs. But some specific variants ARE a different tube.
I had some experience with 6dj8 family tubes: Amperex(Holland made), Siemens(German made), Philips(US made), and Sylvania(US made).
From my experience, on Amperex and Siemens, 6dj8 sounds the best, more air and warmth as well as frequency extension, compared to 6922 and 7308 version of same makers. 7308 sound the worst, bright, tinny, little harsh. And 6922 being in between 6dj8 and 7308. Funny thing is that 7308 is supposed to be the best in specification and 6922 is spec'ed for military use with long life compared to 6dj8. I guess best spec don't always yield best sound. On Amperex and Siemens, you can identify 6dj8 from 6922/7308 from their construction and date code.
One the other hand, Sylvania and Philips, both JAN 6922 and normal 6dj8 sound almost same if not same. Would it because they were all produced in same line but different label???