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Thread: Help me identify some 12ax7 tubes, please?

  1. #1
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    Help me identify some 12ax7 tubes, please?

    I recently got a few old 12ax7/7025s which I would like to determine the origins of.

    I've got 4 that are labelled, and I'm trying to figure out who the actual manufacturer is, here are links to pics of them:

    RCA (you can faintly see in one pic "HOLLAND": vwtweaked.ca - /images/12ax7s/rca/

    Two identical sylvanias (one of which I believe says made in Hungary in pic IMG_5591.JPG its hard to see in the pic but I can make out an H an N and a Y):
    vwtweaked.ca - /images/12ax7s/sylvanias/

    Westinghouse: vwtweaked.ca - /images/12ax7s/westinghouse/

    And then I have this one which I can't make out any label other than 12ax7:
    vwtweaked.ca - /images/12ax7s/unknown/

    Any help in identifying this would be greatly appreciated.

  2. #2
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    1. Philips (I see a Delta mark)
    2. Tungsram Hungary
    3. not sure. Micas make me think RCA, but not positive
    4. I'd guess RCA (octagon, plus residual orange lettering, plus overall appearance, internals(long plates so prob. earlier)

  3. #3
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    Cool, thanks for the info. I was thinking the first one was possibly amperex, being from holland, and rebranded as RCA.. and then I guess I've also read about some tubes being "amperex, a phillips tube company".. Any thoughts?

    Quote Originally Posted by dai h. View Post
    1. Philips (I see a Delta mark)
    2. Tungsram Hungary
    3. not sure. Micas make me think RCA, but not positive
    4. I'd guess RCA (octagon, plus residual orange lettering, plus overall appearance, internals(long plates so prob. earlier)

  4. #4
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    gee, I forget the particulars but Philips owned a lot of factories and had many relationships with other tube makers so there is a big connection with other brands such as Mullard, Valvo and a lot of the 12AX7/ECC83s look very similar. I would google for the history and if it's of interest the Philips tubes factory codes (widely avail. on the web).

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    3 and 4 definitely RCA , 1 and 2 not sure.

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    I contacted steve from thetubestore.com.

    Regarding 1 he said:
    On first glance it looks like an RCA 7025.

    But I see "HOLLAND" printed on the tube and in the second photo I can see an alpha sign on the bottom of the tube. ( on the opposite side of the glass )
    This telling me it is an Amperex 7025

    The way 7025 is printed on the glass is how Amperex printed the tube type.
    RCA would usually print the tube type in an octagon shaped box in dark lettering.
    The tube appears to be made in 1957.

    Regarding the second one he said:
    This tube is labeled Sylvania but was manufactured by Tungsram.
    You can tell a Tungsram 12AX7 by the oval shaped holds in the plates,the thick getter support rods and the square "flag" with a number stamped on it welded to the getter support rod.

    He also said 3 was likely RCA, and that the 4th one is RCA. So I think this is all sorted out for me.

    I'm experimenting with preamp tubes in my orange ad30htc. For my clean channel my favorite combo of preamp & PI tube is the longplate RCA in v1, and the amperex tube in v2, it sounds very nice.

    I'm still not 100% happy with my dirty channel though. Any combination of the other RCA with the Tungsram just seems a bit too thick sounding and honestly almost a bit scooped and too creamy, the amp is already pretty dark so I'm trying to find out what would work good to bring out the articulation of each string when playing chords and maybe be a bit brighter. Maybe I should start a new thread for this, but I'd be interested to hear any suggestions on a couple other tubes to try for my dirty channel.

  7. #7
    Supporting Member Alex R's Avatar
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    Chinese 12AX7 sound good.

    As to tube number one, I think you're probably by now the world authority on whether or not it's an Amperex. Seriously, I suspect that no-one knows any more for sure who made which tubes for whom back in the day - though, of course, there are plenty of people with very definitive views out there. Usually with tubes to sell.

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    Quote Originally Posted by Alex R View Post
    As to tube number one, I think you're probably by now the world authority on whether or not it's an Amperex.
    Why would you say that? I really don't have anything to compare these tubes to, old vintage tubes are a new thing to me.

    After playing around with all of the tubes though, I do like the two tungsrams in my dirty channel the most.

  9. #9
    Supporting Member Alex R's Avatar
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    I mean, you may not get a more definitive answer to your question, and you are probably already in possession of all the available knowledge on the issue. I doubt whether tube manufacturers who contracted some work out would wish that information to be made public, so most of it's going to be lost in the mists of time by now.

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    Quote Originally Posted by Alex R View Post
    I mean, you may not get a more definitive answer to your question, and you are probably already in possession of all the available knowledge on the issue. I doubt whether tube manufacturers who contracted some work out would wish that information to be made public, so most of it's going to be lost in the mists of time by now.
    True enough. Whatever it is, I think I've figured out where I like it in the amp. Figuring out what I liked about these tubes has been a test and listen exercise for me, but it is nice to know what it is I'm actually listening to, just for future reference.
    Thanks again to everyone that's helped in identifying the tubes.

  11. #11
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    tubes are identifiable. It's not some unfathomable mystery, you just have to figure it out. For the 1st one for example, you've got the seams in top, overall bottle shape, plate structure("ladder" which is prob. one of two lengths), presence of etched code, any markings visible, other existing examples, measurable electrical characteristics, etc. Etched code looks like "delta", so Philips, Heerlen, Holland.

    http://www.triodeel.com/images/philipstubecodes.pdf

    It's not a big deal today with the internet because you can get so much data (pictures, codes, personal knowledge from people living in various countries, people sharing info, etc. etc.).

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