Help identifying these 12AX7 tubes

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers T' started by RyanPitch, Jan 8, 2009.

  1. RyanPitch

    RyanPitch Member

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    Can anyone shed light on these tubes? Any info would be greatly appreciated.

    From V1: [​IMG] [​IMG]
    This tube says "Pro/Comm" on it. Never heard of that badge, but I'm guessing the "Made In Germany" can help someone identify it. Approximate age or other name brand equivalent? I assume that bent pin on the left photo is a bad thing...

    V2: [​IMG]
    There's just about nothing left with which to identify this tube. There's a small amount of orange paint left right in the front there that looks like it used to say, "Made..." or something like that. See that M?

    V3: [​IMG] [​IMG]
    Obviously branded "RCA" and it says "U.S.A." Can you tell me anything about it - Longplate, short plate, ribbed, blackplate, etc. Thanks in advance.
     
  2. TweeDLX

    TweeDLX Member

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  3. gldtp99

    gldtp99 Member

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    V1--? odd short folded plates
    V2-- Tungsram (Hungary)--- good tube in Marshalls
    V3-- RCA 7025---- Lo noise version of 12ax7---- grey ribbed plates---one of my favorite tubes in most amps--- i see few RCA 7025's in decent shape so i use more RCA 12ax7a's
     
  4. Timbre Wolf

    Timbre Wolf GoldMember Support Group Gold Supporting Member

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    V1 is RFT - early breakup, rolled-off highs, great for lead playing in bright sounding amps

    V2 is Tungsram - sort of like a short-plate Mullard, but more high-end detail and crunch

    V3 is RCA - excellent bright detail (for a short-plate 12AX7 type), and much more clarity when compared to its identical-looking 12AX7A RCA sibling. Emphasis is on fundamental tones; i.e. not as harmonic-rich as Mullard (and other Philips) short-plate 12AX7A types

    ~ Thom
     
  5. rockon1

    rockon1 Member

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    Elementary my dear Watson! :p Dang! I missed an easy segment of "Name that Tube!" Bob
     
  6. Timbre Wolf

    Timbre Wolf GoldMember Support Group Gold Supporting Member

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    Yeah - I knew that if you'd gotten here first, it'd be all over, and all I could say was "yep." :cool:

    ~T
     
  7. RyanPitch

    RyanPitch Member

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    Thanks for your help. I did some preamp tube testing/swapping today after reading books by Dave Hunter, Gerald Weber, and some other dude. It was the first attempt I ever made to hear the difference between preamp tubes.

    I have a Soldano Decatone and first tried swapping V1 with these three tubes (above), a Groove Tubes 12AX7, and a Sovtek 12AX7LPS (i.e., what came in the Soldano). I only really played on channels 2 and 3 (lead) since that's a lot of what I play. I heard almost no difference between any of the tubes (signal chain was a Gibson SG standard into Decatone, no pedals, and that into a Bogner 4x12 slant cab with Vintage 30s).

    Then Bill Sundt at Soldano said to try swapping V2 since that's strictly dedicated to the overdrive channel. Same results. I heard just about no difference between any of the tubes.

    Weird. I'm just getting into this, but I think the next thing I'm going to try is to bias the amp slightly over and under bias and see what my ears like. Are the differences between preamp tubes only noticeable when you have a less complex circuit between your guitar and speaker? Are the differences more noticeable in single channel vintage amps? Is it harder to discern in hi gain situations?
     
  8. jcs

    jcs Supporting Member

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    imo you will hear more clarity with nos tubes (as a whole) when pushed really hard with od pedals, also listen for more clarity in the lower end.

    as far as nos tubes go, some guitar circuits dont matter as much as others and often times you can find good sounding examples of new production too,you just have to try a bunch and spend some time with them to hear for yourself imo..
     

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