Help me ID this Mullard Tube

Discussion in 'Amps and Cabs' started by tonesurfer, Dec 20, 2009.

  1. tonesurfer

    tonesurfer Senior Member

    Messages:
    1,196
    Joined:
    Sep 19, 2009
    Location:
    Richmond, VA
    The logo is mostly worn off.

    It had a white shield and has a made in great britain on the bottom.

    I'm trying to find out exact ID info about this tube so I can find another from the same batch because it sounds damn good!

    [​IMG]
     
  2. tonesurfer

    tonesurfer Senior Member

    Messages:
    1,196
    Joined:
    Sep 19, 2009
    Location:
    Richmond, VA
    I found the code on the bottom of the tube: B2A4 (no code above it though)

    So would that mean this tube is from the 4th week of January, 1972?
     
    Last edited: Dec 20, 2009
  3. Jeff West

    Jeff West Member

    Messages:
    857
    Joined:
    Mar 26, 2003
    Location:
    Houston, TX
    No, this one was made late January 1962. Other code if you could find it would be "I61".

    Happy holidays-

    Jeff W.
     
  4. tonesurfer

    tonesurfer Senior Member

    Messages:
    1,196
    Joined:
    Sep 19, 2009
    Location:
    Richmond, VA
    May I ask how you can tell it's I61? The I6X code is definitely missing!
     
  5. Jeff West

    Jeff West Member

    Messages:
    857
    Joined:
    Mar 26, 2003
    Location:
    Houston, TX
    Hi Mike- Yeah, the type codes are more vulnerable to disappear on these from wear, for some reason. On Blackburn-made Mullard 12AX7 shortplates the I61 type/batch code was used from their first appearance in about 2/59 until spring/summer of 1964 (all dates going by the factory/date manufacture etch codes). There were a few Blackburns coded "I62" in April and May '64, maybe by mistake, but they switched around then to "I63" for the remainder of Blackburn production of these, through the '60s and most of the 1970s. Note that "I61", "I62", "I63" as well as other "I6" type codes also were etched on shortplate 12AX7s made by several other Philips factories during the '50s-'70s, sometimes overlapping with Blackburn and sometimes not.

    There are several clues for students of Philips tube minutiae that can tell you that the one you pictured with that code is '60s not '70s, inc logo, getter arrangement, etc. but the easiest dead giveaway in that photo that can account for all the variance by itself is the bright copper of the grid rods protruding above the mica. In Blackburn Mullard short plate 12AX7s those rods were copper from about 1/60 through earliest months of 1966, I61 versions earlier in '59 as well as I63s from early '66 on invariably had silver colored rods. It's also a way to tell Mullard ECC83s from ECC82s in this early '60s period if the type codes and labelling are gone, the 12AU7s had silver rods throughout. In the case of 12DW7/7247s from this period, the 12AX7 side has copper, and the 12AU7 side has silver!

    Most importantly, glad that's a good sounding one to you. I can definitely, um, relate to the idea of getting spares with the same codes when you discover a great sounding specimen, but take it from me they don't always sound identical even when made in the same factory in the same week. Couldn't hurt to try though!
     
  6. tonesurfer

    tonesurfer Senior Member

    Messages:
    1,196
    Joined:
    Sep 19, 2009
    Location:
    Richmond, VA
    Thanks for the info! I have some early 70s mullards and they just don't sound very good to me. This one however sounds very special. I was thinking maybe the 60s ones in general sounded better or in particular this I61 variety. Bummer if it's a crapshoot though at least I found a great one.
     

Share This Page