Box marked RCA 12AU7

Discussion in 'Tube Audio' started by Trojan4Life, Jan 13, 2018.

  1. Trojan4Life

    Trojan4Life AK Subscriber Subscriber

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    But the tube is Amperex.

    Amperex.jpg

    Another one looks different, has the gettering on the side of the tube.

    RCA Clear.jpg

    Is this an error, or did someone use the wrong box? These tubes are from the tube collection I was given late last year. I've been trying to categorize the tubes, put the same number tubes together and add them to a spreadsheet.
     
  2. Blue Shadow

    Blue Shadow I gotta get me a new title

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    A box is a box. It doesn't specify what is inside unless it has never been opened and contents removed, leaving the empty box as a home for either the removed tube or some other tube that doesn't have a box.

    Probably gonna need to test the tubes to see if you have something or just used tubes. Hopefully you have a couple nice ones there, put into boxes because they are the good ones.
     
  3. jaymanaa

    jaymanaa AK Subscriber Subscriber

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    You got lucky if that BB tests good. I had the same thing happen at a garage sale once, picked up a tungsol 12AX7 box and it had a BB in it. I think the old guys weren't sure if some tubes were good or bad (maybe the tester was back at the shop) and stuck the tube they replaced in the box from the new tube.
     
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  4. Trojan4Life

    Trojan4Life AK Subscriber Subscriber

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    Some background: These tubes were given to me late last year by my neighbor who recently retired from JPL. At the time, I owned two tube amps. He was an EE who was into tube amps (guitar and audio amps) and his hearing went bad.

    My question is based on the majority of these boxes look like they have never been opened, or haven't been opened for decades. I am testing many of the output tubes and some of the driver tubes, don't have any amps right now that use these particular tubes and just wanted to get more info.

    I just don't know why or if RCA would have ever put Amperex tubes in their boxes? Why does the tube with gettering on the side look different from the others? (The rest have gettering on the top). Did RCA make some 12AU7 tubes that looked like this?

    Thanks for your help, Blue.
     
  5. mroboto

    mroboto Super Member

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    The tube with clear top is called " Clear top" , RCA made clear top tube.

    RCA didn't boxed an Amperex Buggle Boy in their box.

    But someone afterwards use this box because the original (If it has one) was lost and there was an empty RCA box available..
     
    Last edited: Jan 13, 2018
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  6. Trojan4Life

    Trojan4Life AK Subscriber Subscriber

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    Ok, thanks for your reply. I found 24 of these Amperex tubes in RCA boxes and 64 of these clear top RCA tubes in the tubes I was given.
     
  7. mroboto

    mroboto Super Member

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    Weird.
     
  8. Trojan4Life

    Trojan4Life AK Subscriber Subscriber

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    It is...

    This tube collection dates back to the early 1960s. No telling what happened. It's difficult to communicate with the original owner because he can't hear very well, even with his hearing aids. I'm going to send him email...
     
  9. FlaCharlie

    FlaCharlie Active Member

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    It was common practice for techs to put the tube that was replaced into the box of the new tube that they had used to replace it with. Lots of tubes that were replaced were not necessarily bad, although many tested weaker than the new replacement. Also, some techs were known to replace an extra tube or two in order to make a little extra money. RCA also made some clear top versions of 12AX7s. Test them and see if they're good enough to be usable. I've bought many batches of tubes and I've found many boxes with tubes inside that are obviously used and often a different brand.
     
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  10. sKiZo

    sKiZo Hates received: 8641 Subscriber

    ... be more unusual here to find any of my tubes in the RIGHT boxes - or in boxes at all come to think of it.

    PS - refresh my memory. Amperex was Mullard (Holland), right?
     
  11. Tom Bombadil

    Tom Bombadil AK Member

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    You were given 88 12AU7 tubes? How many tubes in all? That's quite a gift.
     
  12. Duke58

    Duke58 Well-Known Member

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    Tom- my neighbor gave me nearly 800 tubes. And two tube testers, although one is out for repair and calibration. Includes output tubes, rectifier tubes, tubes that start with 5, 6, and 12. There are lots of 5687, 6201, 5U4G, 5Y3GT, 5881, 6L6 metal and glass, 6V6, EL34, 8068, 6BG6, etc. Most of the tubes are RCA with a mix of Sylvania, Mullard, Raytheon, Amperex, Toshiba. I even have dozens of boxes of matched tubes from Tektronix with serial numbers on them, Siemens 6922, 5687, 5751, CK5814, EL84, 6U8A and those are just the tubes I'm familiar with.

    And yes, I've taken him out to dinner at least twice, go over and see if he needs anything. He's hard of hearing and it's difficult to talk to him in person. My wife will cook him a meal and I take it over.

    I recently bought a tube amp from AK member Primosounds. I can roll several different tubes through the amp. Listening to it right now with EL34 outputs, 5AR4 rectifier and a 6SL7GT driver installed, using my Cornwall speakers. Sounds great!

    Normally, I wouldn't have gotten into tube rolling, but with all these tubes, what would you do?
     
  13. Dswankey

    Dswankey Super Member

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    Last edited: Jan 13, 2018
  14. MannyE

    MannyE Exterminate! Subscriber

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    That's nice. I bet he might enjoy seeing/maybe hearing that setup. Put in some ear plugs and blast some music for him one day when the wife is away. I bet he'll get a kick out of it. :)
     
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  15. Andyman

    Andyman Scroungus Stereophilus Subscriber

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    Well, the Bugle Boy Amperexes are probably more valuable than the RCA , especially if they have certain getter and plate qualities, like a foil D getter. The RCA cleartops are probably worth less than blackplates, but both are said to be nice sounding tubes.

    Looking at your list, that's a very respectable haul of tubes, many could be of above average values, especially EL34, glass 6L6 and the variants, 5881, 5751, 6V6 and EL84. The 6U8, 5U4 are not expensive, and while Kegger likes the 6BG6's sound, they rarely bring $10/each.

    That was quite a gift!
     
  16. PakProtector

    PakProtector AK member

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    If you have matched 12BY7's the Citation II folks will find them quite useful. For that matter, those are quite useful for LTP( though pentodes rarely get used in LTP's ). In E-Linear circuits they are quite fine; it saves finding pairs from a pile of singles...:)
    cheers,
    Douglas
     
  17. gadget73

    gadget73 junk junkie Subscriber

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    Thats the later RCA logo, so these don't date from the early 60s. I think that logo was '68 or so. Early 60s was still the "meatball" logo.

    but yeah, someone probably swapped a tube and put the Amperex in the RCA box. It happens.
     
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  18. Trojan4Life

    Trojan4Life AK Subscriber Subscriber

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    It happened 24 times. Someone (former owner) swapped 24 Amperex tubes into RCA boxes.

    They all tested "good" on my B&K Model 707.
     
  19. kward

    kward AK Subscriber Subscriber

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    I have a set of these and want to use them for something worthwhile in a scratch build. For a LTP do you run them triode strapped or as pentodes?
     
  20. PakProtector

    PakProtector AK member

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    Depends on the app...like for a linestage, I would probably run triodes( my LTP linestage actually runs triode EL84 ). For a plate-to-grid FB amp, either E-Linear or resistive, pentodes for sure. The key things with this stuff is that the g2 get ref'd to the cathode node. NOT ground, even if the signal on the cathode node is quite small in comparison to the g2 voltage.
    cheers,
    Douglas
     

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