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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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    Bias voltage for KT88s on an ST-70

    polarflux
    polarflux
    polarflux


    Posts : 49
    Join date : 2010-02-12
    Location : Alaska
    • Post n°1

    Bias voltage for KT88s on an ST-70 Empty Bias voltage for KT88s on an ST-70

    Post by polarflux Thu Feb 18, 2010 5:50 pm

    What should the bias be set to when using KT 88's?
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    Bob Latino
    Bob Latino
    Bob Latino
    Admin


    Posts : 3272
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°2

    Bias voltage for KT88s on an ST-70 Empty Re: Bias voltage for KT88s on an ST-70

    Post by Bob Latino Thu Feb 18, 2010 6:08 pm

    First of all in an ST-70 you must have an upgraded power transformer (which you do) to run KT88's. KT88's use about 35% more current than an EL34 and can damage the power transformer in an original ST-70 with a stock PA-060 power transformer.

    Bias KT88's at .500 VDC in any VTA boarded ST-70 with an upgraded power transformer.

    Bob
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