Which tubes can I use with a Rode K2?

Discussion in 'Microphones (live or studio)' started by gunsofbrixton, Feb 17, 2010.

  1. gunsofbrixton

    gunsofbrixton Active Member

    Nov 22, 2009

    I know there's a few forum threads on this topic out there, but none of them quite answers my question. I want to try out a few different types of tubes to replace the standard 6922 tube inside my Rode K2. Do I need to replace this tube with the same type (i.e. 6922 aka ECC88) or can I use different types as well?

    I would assume that the replacement tube should have a gain factor similar to the default tube. Is this correct?

    Here's a list of common preamp tubes and their gain factors:

    12AX7 / ECC83: 100
    12AT7 / ECC81: 60
    12AY7 / 6072: 45
    6922 / ECC88: 33
    12AU7 / ECC82: 19

    From looking at this list, I would assume that I should be able to replace the K2 tube with either 12AY7 or 12AU7. Is this recommended? Also, I found out that the famous Neumann U47 and their clones (e.g. Lawson L47) use EF86 tube types. I don't know their gain factor. Would I be able to use this type in my K2?

    I hope somebody can give me an answer...thanks!
  2. Boswell

    Boswell Moderator Distinguished Member

    Apr 19, 2006
    Home Page:
    The CC in the ECCxx series means double triode. The F in the EF86 means single pentode. You can't replace one with the other. Even within the double-triode series, you have to be careful about swapping between types as the heater connections can be different. All the E series valves have 6.3V heaters, but not necessarily on the same pins - some are centre-tapped and can be run on 12.6V. All this is before you start to consider gains and other operating characteristics.

    I would not change from the fitted type (except perhaps for trying different makes of nominally the same type) without talking first to Rode. They are very human and friendly, and will probably tell you why they ended up with the type they did,
  3. gunsofbrixton

    gunsofbrixton Active Member

    Nov 22, 2009
    ...and fast!
    I wrote them an email today and got an answer within hours. They say that the 6922 / ECC88 type is the only type of tube you can use with the K2.
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