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Discussion in 'Electronic Repair Modifications DIY' started by Link555, Jun 18, 2010.

  1. Link555

    Link555 Well-Known Member

    I have never used a 12BH7 before....

    Two questions:

    1) In Urei LA2 they use a 12BH7 in the output drive section instead of 12AX7(more gain I know) or 12AU7, why is that?

    2) Other that the heater current, what is the difference between a 12AU7 and 12BH7?

  2. Boswell

    Boswell Moderator Distinguished Member

    I've never used a 12BH7 either, but here is a semi-sensible discussion of it, including substitution for a 12AU7.

    The data sheet shows it targeted at TV frame circuits, and it looks at first glance to be a low-mu device capable of handling higher currents than a 12AU7. That may mean it is more suitable for driving output transformers (secondary loaded with 600 Ohm), and so could be why Urei specified it in the LA2.
  3. Link555

    Link555 Well-Known Member

    I am not sure if I am mis reading the data sheets, but its appears that the 12au7 mu is 17
    and the amplification factor of the 12BH7 is 16.5

    They are pretty simular
    JJ ECC802-S / 12AU7 Gold

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