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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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    Tetrode Tubes with Triode Switch Mod on Dynakit St70

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    immemory


    Posts : 2
    Join date : 2021-11-20

    Tetrode Tubes with Triode Switch Mod on Dynakit St70 Empty Tetrode Tubes with Triode Switch Mod on Dynakit St70

    Post by immemory Sat Nov 20, 2021 12:04 pm

    My question involves the new tetrode tubes I bought for my Dynakit kit st 70 with the triode switch mod (I also have the vta 70 driver mod). I recently bought a set of Electro Harmonix 6CA7's which are tetrodes. Does the triode switch as wired work the same as it does with el34 pentodes? I found that the tubes seem to break in better with the triode switch in the back/off position and it got me to wondering if the triode switch functions the same with tetrodes. It sounds great turned off and Im wondering if the switch should be used at all with the 6CA7s.
    Dave_in_Va
    Dave_in_Va


    Posts : 424
    Join date : 2013-04-02
    Location : Mid. VA

    Tetrode Tubes with Triode Switch Mod on Dynakit St70 Empty Re: Tetrode Tubes with Triode Switch Mod on Dynakit St70

    Post by Dave_in_Va Sat Nov 20, 2021 1:41 pm

    I'm fairly sure a 6CA7 is the same tube as an EL34.
    USA - 6CA7, UK - EL34
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    immemory


    Posts : 2
    Join date : 2021-11-20

    Tetrode Tubes with Triode Switch Mod on Dynakit St70 Empty Re: Tetrode Tubes with Triode Switch Mod on Dynakit St70

    Post by immemory Sat Nov 20, 2021 2:21 pm

    Yes its works the same as the el34 without the mod but when you do the triode mod it might not work the same. There are different triode mods for different tubes. Thats my question. With the Hazen triode mod tetrodes apparently have issues.


    Last edited by immemory on Sat Nov 20, 2021 3:04 pm; edited 1 time in total (Reason for editing : additional info)
    peterh
    peterh


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

    Tetrode Tubes with Triode Switch Mod on Dynakit St70 Empty Re: Tetrode Tubes with Triode Switch Mod on Dynakit St70

    Post by peterh Sat Nov 20, 2021 4:06 pm

    immemory wrote:My question involves the new tetrode tubes I bought for my Dynakit kit st 70 with the triode switch mod (I also have the vta 70 driver mod). I recently bought a set of Electro Harmonix 6CA7's which are tetrodes. Does the triode switch as wired work the same as it does with el34 pentodes?  I found that the tubes seem to break in better with the triode switch in the back/off position and it got me to wondering if the triode switch functions the same with tetrodes.  It sounds great turned off and Im wondering if the switch should be used at all with the 6CA7s.
    6CA7 is a beam tetrode just like 6L6 6550 etc.
    And it will be working in triode mode just like an EL34 BUT DO NOT SWITCH UNDER POWER !
    ( the switches dot't cope well with breaking 500Volt DC )

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