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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 products

    transformer primary impedance


    Posts : 269
    Join date : 2011-04-04

    transformer primary impedance Empty transformer primary impedance

    Post by sailor on Fri Aug 31, 2012 3:50 pm

    Just checking to make sure I am correct. 2-El84's in push pull need about 8000 ohms primary impedance. If I double the number of output tubes I would then need about 4000 ohms.
    Am I correct?

    Posts : 1661
    Join date : 2008-11-30

    transformer primary impedance Empty Re: transformer primary impedance

    Post by tubes4hifi on Sat Sep 01, 2012 2:13 pm

    that's correct
    another thing most people don't realize is that if you use a different secondary winding the reflected impedance to the primary changes,
    so instead of using the ratio of 8K to 8 ohms, you could connect to the 4 ohm tap using 8 ohm speakers and the primary impedance will be 4K.
    It's the same transformer ratio 4K to 4 ohms.

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