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    Rectifier Tube Option?

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    t8ter

    Posts : 10
    Join date : 2010-01-03
    Location : Calgary, Alberta

    Rectifier Tube Option?

    Post by t8ter on Tue Feb 21, 2012 11:27 pm

    I was reading an ad for rectifier tubes and the seller stated that a direct replacement for a GZ32,GZ34,5AR4,5U4G, with a slower soft start was a 274B. Has anyone used a 274B, or is a 274B a good replacement tube for a GZ34? I am sure Bob could give me the low down on this tube if no one else can.

    tubes4hifi
    Admin

    Posts : 1286
    Join date : 2008-11-30

    Re: Rectifier Tube Option?

    Post by tubes4hifi on Wed Feb 22, 2012 12:36 am

    you'll probably learn alot more doing a 15 second google search than waiting for answers here,
    but the quick answer is that the 274B is closer to a 5U4G than anything else, and it has several specific requirements for use. It is a directly heated rectifier, and it is only good for about 150ma max current, compared to a 5AR4 which is good for 250ma. Thus, it might be fine in a MK3 amp for example, but definitely not in an ST70 or ST120 amp, as both use much more current. It also requires the first capacitor to be 10uF or less.

    GP49

    Posts : 733
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: Rectifier Tube Option?

    Post by GP49 on Wed Feb 22, 2012 12:40 am

    The specifications say that functionally, the 274B could be a substitute for a 5AR4, except that it actually looks to
    be closer to a 5U4 than a 5AR4; it will drop the B+ more than a 5AR4.

    There is a page with information about the ORIGINAL 1930s-era Western Electric 274B here:

    Western Electric 274B

    However, with prices for original 274B (they date from the 1930s) reaching four figures, WHY would one want to use one?

    There is supposed to be a modern reproduction from China but I (and others) suspect it is actually a "rebottled" and relabeled
    5U4.

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