Hi again Killtone,
Wisdom? :roll: It's more like obsessive compulsion disorder, but thanks for your welcome compliment! :wink:
Check out the RCA 12ax7 thread in the tubes section if you haven't yet and take a look at the link to "tube classics" one of the posters included there, I'm sure that will help also. Shredd's posts there are visually and factually illuminating.
Would still enjoy seeing pics of your new tubes, that would be the best if possible (if not too much a pain in the ass for you to do.) That would help, I'm not sure from your description whether you have short or long plate tubes. Short plates are approximately 15mm in length, long plates are 17mm. If a ruler is not handy, the short plates appear to be about equal in length to the width of the bottle, the long plates appear to be longer than the bottle is wide. The ladder with three rungs you mention is called a ribbed plate. The ribs are there to stiffen the plates and hopefully reduce microphonics. Take a look at a Telefunken smooth plate on Ebay, you will see long plates with no ribs.
Yes, there is such a thing as Amperex labeled Mullards. The acid etch tells all. I have several of them. Mine have a slightly fatter sound similar to the Mullard 10m 12ax7's and Philips lableled 12ax7a/7025a's, along with a similar purplish deposit inside the bottom of the (well-used) bottle from the startup flash common to those three types. Most flash marks tend to a silver-gray color in the Amperex, Mullard, and Philips shortplates I have.
Amperex, Philips Miniwatt, Philips, Mullard, and Siemens were all owned by their parent company, Philips at one time. There are subtle differences in the designs, but there is a "Philips family tone" to the tubes with similar constructions. The short plate ones tend to be more lower mid-bassy, the long ribbed plate ones tend to more upper mid-top end detail. Later on, Matsushita purchased the shortplate tooling from Mullard, and made tubes, the "Japanese Mullards" with the 45 degree angled getter flash are VERY well made and have the family tone, although it is brighter on top, even more so than the shortplates coming out of the Heerlen, Holland Amperex family, the Japanese Mullards are one of the great values in vintage tubes today on ebay.
I have also noticed a particular "family tone" in the Raytheon blackplate 12ax7's, 5751, 12at7, and 12au7 as well.
Does the German tube's getter ring have one support or two? Siemens generally have two supports, but not always. Also, I have seen vintage Siemens shortplate 12ax7's on ebay with Mesa silkscreening. The Siemens shortplate types are my faves for tones out of the Philips family of shortplate 12ax7's. Siemens also made a triple mica shortplate top end quality 12ax7 to compete with the Telefunken ecc803s, the Siemens is called e83cc/12ax7wa. Have several in Siemens and Philips labeling. They are spendy, but not nearly as much as the 'funkens that go for 400+ bucks apiece nowadays. I like to think that Siemens might have been pretty cocky about their tubes, as the mathematical "not equal" sign etch code suggests, get it, no equal...
Peace.
