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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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    vta st70 driver board tube option

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    detoxer


    Posts : 10
    Join date : 2011-08-17

    vta st70 driver board tube option Empty vta st70 driver board tube option

    Post by detoxer Wed Dec 05, 2012 10:26 pm

    Would it be possible to sub 6n6p tubes for 12bh7 in the vta st70? confused
    Roy Mottram
    Roy Mottram
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    Posts : 1838
    Join date : 2008-11-30

    vta st70 driver board tube option Empty Re: vta st70 driver board tube option

    Post by Roy Mottram Thu Dec 06, 2012 4:58 pm

    try it, and let us know . . .
    it does require more filament current 750ma VS the usual 300ma of a 12AU7 or 600ma of a 12BH7
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    detoxer


    Posts : 10
    Join date : 2011-08-17

    vta st70 driver board tube option Empty Re: vta st70 driver board tube option

    Post by detoxer Mon Dec 10, 2012 9:33 pm

    will I have to rewire the filament pin out?
    Roy Mottram
    Roy Mottram
    Admin


    Posts : 1838
    Join date : 2008-11-30

    vta st70 driver board tube option Empty Re: vta st70 driver board tube option

    Post by Roy Mottram Mon Dec 10, 2012 10:04 pm

    yes, definitely, the connecting trace between pins 4 & 5 on each tube of the VTA70 driver would have to be cut,
    and these tubes would use a total of 2.25 amps of filament current compared to the 0.90 amps of current for 12AU7s,
    which is also the same 0.90 amps used by the two original Dyna 7199 tubes. Hope you like hot power transformers!
    If you really decide to go for it, I'd recommend adding an extra 6v filament transformer rated at 3 amps,
    or maybe just a 1a one to run the center tube

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