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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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    Setting bias on Mk 3 -- speaker connection required?

    jrethorst
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    jrethorst


    Posts : 39
    Join date : 2009-02-01
    • Post n°1

    Setting bias on Mk 3 -- speaker connection required? Empty Setting bias on Mk 3 -- speaker connection required?

    Post by jrethorst Sat Jul 31, 2021 9:32 pm

    Not knowing much, I'd thought that SS amps had to have speakers connected when you turned them on, while tube amps with output transformers did not. I just read that tube amps do need speakers connected, otherwise the output transformer may become damaged.

    No worries if tube amps need speakers connected before you hit the power switch, but what about when you're biasing the amp? The Mk 3 instructions say turn on the power with the rectifier tube not installed, etc. No mention of a speaker. I ask because when my amps are set in the cabinet where the speaker wires can reach them, they're not in a convenient place to work on.

    Thanks,
    John R.


    Last edited by jrethorst on Sat Jul 31, 2021 9:35 pm; edited 1 time in total (Reason for editing : clarification)
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    Bob Latino
    Bob Latino
    Bob Latino
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    Posts : 3277
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°2

    Setting bias on Mk 3 -- speaker connection required? Empty Re: Setting bias on Mk 3 -- speaker connection required?

    Post by Bob Latino Sun Aug 01, 2021 7:39 am

    jrethorst wrote:Not knowing much, I'd thought that SS amps had to have speakers connected when you turned them on, while tube amps with output transformers did not. I just read that tube amps do need speakers connected, otherwise the output transformer may become damaged.

    No worries if tube amps need speakers connected before you hit the power switch, but what about when you're biasing the amp? The Mk 3 instructions say turn on the power with the rectifier tube not installed, etc. No mention of a speaker. I ask because when my amps are set in the cabinet where the speaker wires can reach them, they're not in a convenient place to work on.

    Thanks,
    John R.

    Hi John,

    You should have your speakers connected every time you turn the amp on with all tubes installed. Yes - if you don't have the rectifier installed, it won't cause a problem if no speakers are attached. On some tube amps if you don't have speakers attached, it may be difficult to set the bias. Some tube amps will give an unsteady, "wandering bias" with no load (the speakers) on the output transformers.

    Bob

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