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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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    Dyna Mk lll question

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    MarkS57


    Posts : 3
    Join date : 2022-07-18

    Dyna Mk lll question Empty Dyna Mk lll question

    Post by MarkS57 Mon Jul 18, 2022 10:05 pm

    Hi folks,

    New member here, been messing with Dyna's for over 40 years. Recently, I've been working on a set of Mk lll's. One appears to be factory wired. The other no doubt was a kit. I've restored them and kept the stock configuration w/ new PCB's (one of the original boards from the kit was a mess and had to be replaced so I replaced both to keep symmetry). Something I've never seen before- the kit has an original red plug on the original cord; any significance to that?
    Anyway, what current output tubes & rectifier tubes hold up in these guys? Not exactly a low voltage amp.

    Thanks,

    Mark
    peterh
    peterh


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

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    Post by peterh Tue Jul 19, 2022 1:52 am

    MarkS57 wrote:Hi folks,

    New member here, been messing with Dyna's for over 40 years. Recently, I've been working on a set of Mk lll's. One appears to be factory wired. The other no doubt was a kit. I've restored them and kept the stock configuration w/ new PCB's (one of the original boards from the kit was a mess and had to be replaced so I replaced both to keep symmetry). Something I've never seen before- the kit has an original red plug on the original cord; any significance to that?
    Anyway, what current output tubes & rectifier tubes hold up in these guys? Not exactly a low voltage amp.

    Thanks,

    Mark
    JJGZ34 and JJ 6550 work well in these.
    To protect GZ34 of all brands the "yellow sheet mod" is recommended where
    1n4007 diodes are connected in series with the rectifier plates
    WLT
    WLT


    Posts : 173
    Join date : 2013-07-13
    Location : Rochester NY

    Dyna Mk lll question Empty Re: Dyna Mk lll question

    Post by WLT Tue Jul 19, 2022 10:19 pm

    You never stated if you had any of the original tubes. If so the original GZ34 was a Mullard and if they are good they are the ones to use. Depending on vintage they may have GEC KT88 or Tungsol 6550s for output tubes. Those would be great as well. Assuming you have none of these then go with PeterH recommendations for new tubes. If you can find good used vintage original ones at a decent price they are very good. The difficult part is finding good used ones at a reasonable price.
    avatar
    MarkS57


    Posts : 3
    Join date : 2022-07-18

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    Post by MarkS57 Wed Jul 20, 2022 6:56 pm

    WLT wrote:You never stated if you had any of the original tubes. If so the original GZ34 was a Mullard and if they are good they are the ones to use. Depending on vintage they may have GEC KT88 or Tungsol 6550s for output tubes. Those would be great as well. Assuming you have none of these then go with PeterH recommendations for new tubes. If you can find good used vintage original ones at a decent price they are very good. The difficult part is finding good used ones at a reasonable price.

    Hi no I do not have the originals, long gone. I have a set of matched quad Sylvania 6550's from years ago but those are my last resort on anything. I have a few home built 6550 amps where I use SED KT88's & 6550's. Those tubes can handle voltage as most of these amps are higher in B+ than even the Mk lll. Seems over the years Reflector / JJ / Sino never had a good rep for handling voltage, other mfg's I know nothing about. EI was another that could handle voltage but also long gone.
    peterh
    peterh


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

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    Post by peterh Thu Jul 21, 2022 1:45 am

    MarkS57 wrote:
    WLT wrote:You never stated if you had any of the original tubes. If so the original GZ34 was a Mullard and if they are good they are the ones to use. Depending on vintage they may have GEC KT88 or Tungsol 6550s for output tubes. Those would be great as well. Assuming you have none of these then go with PeterH recommendations for new tubes. If you can find good used vintage original ones at a decent price they are very good. The difficult part is finding good used ones at a reasonable price.

    Hi no I do not have the originals, long gone. I have a set of matched quad Sylvania 6550's from years ago but those are my last resort on anything. I have a few home built 6550 amps where I use SED KT88's & 6550's. Those tubes can handle voltage as most of these amps are higher in B+ than even the Mk lll. Seems over the years Reflector / JJ / Sino never had a good rep for handling voltage, other mfg's I know nothing about. EI was another that could handle voltage but also long gone.

    JJ 6550 will work fine in MkIII. Visit Eurotubes.com for matched pairs/quads
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    MarkS57


    Posts : 3
    Join date : 2022-07-18

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    Post by MarkS57 Thu Jul 21, 2022 9:01 am

    [/quote]

    JJ 6550 will work fine in MkIII.  Visit Eurotubes.com for matched pairs/quads
    [/quote]

    OK, I'm going to start with my Sylvania's as a baseline then go to the JJ's. Eurotubes in new to me and it seems they do significant screening.

    Thanks,

    Mark
    peterh
    peterh


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

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    Post by peterh Thu Jul 21, 2022 9:52 am

    JJ 6550 will work fine in MkIII.  Visit Eurotubes.com for matched pairs/quads
    [/quote]

    OK, I'm going to start with my Sylvania's as a baseline then go to the JJ's. Eurotubes in new to me and it seems they do significant screening.

    Thanks,

    Mark[/quote]
    Eurotubes does more, the do perfect matching at high working voltage.

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