What is it about the AC30/6 TB.....

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by TimmyP, Feb 24, 2012.

  1. TimmyP

    TimmyP Member

    Messages:
    2,453
    Joined:
    Nov 1, 2007
    Location:
    Indianapolis
    ....that causes EL84s to go microphonic? I don't have this problem with any other amp model (including the Chinese AC30CC). I will admit that our (day job) AC30s get a lot more use than any other EL84 model we have, but it seems odd that I have to replace more microphonic EL84s than 12AX7s in these things.
     
  2. WaltC

    WaltC Member

    Messages:
    2,130
    Joined:
    Feb 21, 2006
    Location:
    Northern CA (Sacramento area)
    Those EL-84s in AC-30's are working a *lot* harder than the 12AX7s. Even though "modern day" AC-30s aren't run nearly as hot as older JMI AC-30s, they still push the power tubes pretty hard and much harder than the pre-amp tubes.
     
  3. Science Amps

    Science Amps Member

    Messages:
    74
    Joined:
    Nov 13, 2011
    Location:
    Portland, OR
    I'll hazard a guess if it's a vintage AC30. Those amps have infamously poor heat dissipation and the tubes get HOT. The elements are more likely to become loose inside the glass envelope because of the excess heat. Next, you play the rock and roll, and the those little loose elements vibrate and get amplified to holy hell. JM2C.
     
  4. Doug's Tubes

    Doug's Tubes Member

    Messages:
    9,789
    Joined:
    Oct 12, 2004
    Location:
    NY
    Well, the combination of the most harsh environment known to tubes(the AC30/6TB combo amps) and current production EL84's which aren't that great lately either.
     

Share This Page