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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


2 posters

    ST120 with no speakers connected???

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    Rbertalotto


    Posts : 94
    Join date : 2021-02-25

    ST120 with no speakers connected??? Empty ST120 with no speakers connected???

    Post by Rbertalotto Sun Nov 20, 2022 10:27 am

    I have a Tubes4HiFi ST120 Tube amplifier I built a couple years ago. I have a number sets of speakers that I like to audition from time to time. It is my understanding that you are not to disconnect speakers from a tube amplifier while it is running or for some time after you have disconnected power or damage will result?

    Can I build a switch box of some type that would put 8ohm resistors on the outputs with the amplifier still on, while I switched speaker leads from one set of speakers to the other.

    If "yes".....What type of switch or circuit would I build for such a device?



    Thanks
    peterh
    peterh


    Posts : 1689
    Join date : 2012-12-25
    Location : gothenburg, sweden

    ST120 with no speakers connected??? Empty Re: ST120 with no speakers connected???

    Post by peterh Sun Nov 20, 2022 12:19 pm

    Rbertalotto wrote:I have a Tubes4HiFi ST120 Tube amplifier I built a couple years ago. I have a number sets of speakers that I like to audition from time to time. It is my understanding that you are not to disconnect speakers from a tube amplifier while it is running or for some time after you have disconnected power or damage will result?

    Can I build a switch box of some type that would put 8ohm resistors on the outputs with the amplifier still on, while I switched speaker leads from one set of speakers to the other.

    If "yes".....What type of switch or circuit would I build for such a device?



    Thanks
    Any switch box that connects the next speaker BEFORE disconnecting the present .
    "Make before break" as they call it.
    NEVER LEAVE OUTPUT OF A TUBE AMP DISCONNECTED !!!
    avatar
    Rbertalotto


    Posts : 94
    Join date : 2021-02-25

    ST120 with no speakers connected??? Empty Re: ST120 with no speakers connected???

    Post by Rbertalotto Sun Nov 20, 2022 1:24 pm

    I was told that p[utting a 100 ohm resistor across the speaker output terminals would not degrade the sound and would protect the output transformers....??
    peterh
    peterh


    Posts : 1689
    Join date : 2012-12-25
    Location : gothenburg, sweden

    ST120 with no speakers connected??? Empty Re: ST120 with no speakers connected???

    Post by peterh Sun Nov 20, 2022 1:30 pm

    Rbertalotto wrote:I was told that p[utting a 100 ohm resistor across the speaker output terminals would not degrade the sound and would protect the output transformers....??
    Yes, this can be seen as an insurance. But i would still never leave the output open. Shorting
    however is no problem for a tubeamp.
    avatar
    Rbertalotto


    Posts : 94
    Join date : 2021-02-25

    ST120 with no speakers connected??? Empty Re: ST120 with no speakers connected???

    Post by Rbertalotto Sun Nov 20, 2022 1:37 pm

    Thanks! I just ordered two 10w / 100 ohm / 5% wire wound aluminum case resistors.....

    Sponsored content


    ST120 with no speakers connected??? Empty Re: ST120 with no speakers connected???

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