Tube ID - 12AX7s

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Riscchip, Jun 17, 2006.


  1. Riscchip

    Riscchip Member

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    I've been trying to organize my preamp tube stash, and came across a couple of odd ones. My ability to ID tubes is limited to what's printed on them, so maybe some folks who can ID them based on their structure can help. Any clue what these are? Re-branded something-or-elses, I imagine.

    First one has "Garnet" printed on it as well as "7025A/12AX7A", an some largely worn off that looks like "160" over "80K5."

    [​IMG]

    Second one has almost all of the writing worn off of it. I can make out "..ermany" which probably read "Germany" at one point, and someone wrote "12AX7" on the glass with a sharpy.

    [​IMG]

    Thanks for any info.
     
  2. goneracin

    goneracin Member

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    First tube is a mullard. That etching probably reads I60 over B0K5
    2nd tube looks to be a ribbed plate telefunken. Look on the underside, between the pins and see if there is a diamond embossed in the glass.

    Bob
     
  3. rockon1

    rockon1 Member

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    The Garnet seems like perhaps a Mullard if the etch code at bottom of tube actually reads B0K5 The B stands for the Blackburn plant in England.Heres a good like for Philips etch codes.
    http://www.tube-classics.de/TC/Tubes/Valvo/Phlipscode.htm

    The bottom one looks like a ribbed Telefunken to me. Check the glass bottom between the pins. If there is a diamond shape molded into the glass there its a Telefunken. HTH-Bob
     
  4. rockon1

    rockon1 Member

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    Damn beat me to it by a minute!:D
     
  5. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    Well, neither of those are in my collection, but I'll hazard a guess:

    The first is a Philips-style 12AX7A, as identified by the plate structure - especially the round holes in the side of the plates. The only choices I know of for those 12AX7A with tilted getter rings are Valvo and Matsushita. The problem is, that the etch codes you've quoted are not for either of those manufacturers. If it was Matsushita, the second line of etch code would begin with "n" and Valvo's would begin with "D". A second line with "B" would be Mullard's Blackburn plant, but I'm sure there wasn't an "I60" type 12AX7A made there ("I61" and "I63" type only). Bit of a mystery to me.

    The second tube may be a Telefunken ribbed-plate version. Again, I don't have any for a positive I.D., but it kind of seems like that. Confirm (or shoot down my theory) by looking for a "diamond" shape on the bottom of the glass, between the pins.

    Hope these rambling details at least help you get a bit closer. Do you like them in your amp(s)?

    - T

    p.s. best not to believe the printing on tubes - so many were re-branded, you really need to learn to identify the guts to get it right. :AOK
     
  6. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    We were all busy, typing away at the same time!! :crazyguy
     
  7. Blue Strat

    Blue Strat Member

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    We need a head on shot at the plates for the first tube. The way the getter is tilted, it could be the Japanese recreation of a Mullard.

    The 2nd tube could be Siemens or Telefunken. Check for the diamond on the bottom. The way the getter is attached to the support rod looks like the Tele signature.
     
  8. Riscchip

    Riscchip Member

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    Thanks guys! I really appreciate your help on this one! As soon as I get back home, I'll take a closer look at these and see about some more info and another photo or two.

    Again, thanks very much.
     
  9. DEMENTED

    DEMENTED Supporting Member

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    I'll buy them....
     
  10. Jeff West

    Jeff West Member

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    Are you sure the first one isn't actually coded "I63 B0K5"?
     
  11. Riscchip

    Riscchip Member

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    Thanks again guys!

    So I gave these a closer look to answer a few questions. Regarding the second one with "ermany" printed on it. It does have a squarish / diamond shape marking on the base. Here is a pic:
    http://www.riscchip.com/guitars/germany2.jpg

    Regarding the Garnet tube, in response to the code, it's tough to read the third digit in the first number, but it's almost certainly a "163" and not a "160" as I previously thought, but I had to get in there with a mangifier to see this. So it looks like Timbre Wolf and Jeff West were right with that. Also, it's definitely a "B" and not an "8" as I had thought in the second number. BOK5 is the sequence for sure. Here is the sequence as best as I could get it with my camera:
    http://www.riscchip.com/guitars/garnet4.jpg

    I also snapped some shots of the "Garnet" tube from other angles here:
    http://www.riscchip.com/guitars/garnet2.jpg
    The tube has an unusual seam in the top, not sure if that is damage or not (the tube works perfectly):
    http://www.riscchip.com/guitars/garnet3.jpg

    You guys are the best for helping me out here. This is very interesting info about these tubes.
     
  12. Jeff West

    Jeff West Member

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    Yes, I had written a more complete response in the above post but somehow most of it didn't get posted, I must have deleted something right before "submit"(!).

    I agree with Bob R. that it's very likely, I'd say almost certainly a British Mullard, made at the very end of Nov 1970 at Blackburn factory. The gist of what I said was: I've seen a couple of other "Garnet" branded 12AX7s and they were both genuine 1970 Blackburn Mullards, that very year, as it happens. But it would have to be "I63"; "I60" doesn't make sense in any scenario for this tube based on info available (including the "Garnet" brand itself). Contrary to what you might hear, the codes can and do rub off or smear around on these, especially of this particular vintage, they're not nec "etched for life" (in general, Blackburn codes are more resistant than some other Philips though; Heerlen and Munich Siemens are about the worst for disappearing!). Yes, the getter halo is canted more than usual on this specimen, it's a little wierd, but OTOH it does have the bent-at-a-right-angle support rod which would be typical on a '70 Mullard I63. Angled halo/getter Matsushitas and Hamburg Valvos don't have a rod at all, BTW, the halo is welded right to the plate tab. Earlier Blackburn versions have a straight rod and the halo's welded perpendicular to it.

    Two seams molded in the glass at the top appear on all Mullards (four, on earlier ones, and there's some variation), but also on lots of other Philips so that would only be telling if it didn't have the two seams at all.

    I'm assuming that, if you look at the plates perfectly edgewise (not straight on), you do not see any holes on the inside portions of the plates that show grids, or anything else, no circular holes at all. If you do see circular holes on the inside portions of the plates, it's no Mullard. I'm not talking about the rectangular "staple holes" that crimp the plates together, those go through. If you look at the plates head on, there are the folded-at-90 deg half circle holes on the sides of the raised portion in the middle of the plate and outside flat "wings" of the plate, but they shouldn't extend into the inside portion. If they do, could start thinking Japanese or Indian manufacture! But I don't think that's going to be the case here.

    Whew, maybe too much info . . . just enjoy the tube!

    Jeff W.
     
  13. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    Thanks for the details, Jeff. I always learn a little more, and I definitely appreciate the information - never too much for me!

    - T
     
  14. Riscchip

    Riscchip Member

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    What can I say, you guys are the best! Thanks for the information. I guess I should stick these into one of my amps instead of leaving them in the drawer. :nono

    The Garnet / Mullard came out of an ADA MP-1 preamp I sold years ago. Obviously not original equipment. I remember thinking "Garnet? Huh?" (assumed it was crap) and put a fresh Sovtek in there for the buyer. :roll

    Well, for my personal organization purposes, I'll call them a Mullard and Telefunken and call it day.

    Thanks again!
     
  15. BTO

    BTO Member

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    Garnet tubes are rebranded Mullards. I got this info directly from the source...Gar Gillies. He still has boxes of NOS Garnet branded Mullards (12AX7's and EL34's) at his shop here in Winnipeg.
     
  16. Jeff West

    Jeff West Member

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    Cool confirmatory info - we should have just asked you first! "BTO", eh . . . hmm.

    I wonder how long he did that, were the 12AX7s in one big batch? Seems like the few I've seen are all late '70, maybe early '71.

    Someone else just told me he has one (Garnet/Mullard ECC83), I'll ask him to check it . . .

    Jeff
     
  17. BTO

    BTO Member

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    I worked for Garnet assembling combo amps my senior year in high school. A few of my close friends who were a couple of years older than I, did most of the wiring on the chasis'. I had a BTO up until a few months ago, great amp just too damn loud.

    When I was at Gar's shop he had about four, 4 drawer filing cabinets full of individual boxed tubes...some new, most old. He also had some unopened shipping boxes of tubes from the UK that went back to the 70's.
     
  18. Jeff West

    Jeff West Member

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    Thanks for the great info, BTO.

    The other thing I'd be really curious about, if you got a chance to ask sometime, is how the process went to get different logos put on, was that arranged directly through Philips/Mullard and done in England, by third party, etc.?


    Jeff W.
     

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