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    Stock Dynaco ST-70 using 7199, 6GH8A and 6U8 tubes - video

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    Bob Latino
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    Join date : 2008-11-26
    Location : Massachusetts

    Stock Dynaco ST-70 using 7199, 6GH8A and 6U8 tubes - video

    Post by Bob Latino on Wed Sep 04, 2013 2:09 pm

    Below is a video of someone using 7199, 6GH8A and 6U8 driver tubes in a stock Dynaco ST-70 and comparing the distortion levels or each tube. If you have a stock type board and you were thinking of using 6GH8A adapters because 7199 tubes are getting expensive, this would be a good video for you to check out ..

    Bob



    hawaii.ken

    Posts : 157
    Join date : 2012-01-31

    Re: Stock Dynaco ST-70 using 7199, 6GH8A and 6U8 tubes - video

    Post by hawaii.ken on Wed Sep 04, 2013 4:25 pm

    Thanks for posting this, Bob Very Happy


    Last edited by hawaii.ken on Thu Sep 05, 2013 12:51 am; edited 1 time in total

    DarthBubba

    Posts : 81
    Join date : 2012-05-05

    Re: Stock Dynaco ST-70 using 7199, 6GH8A and 6U8 tubes - video

    Post by DarthBubba on Wed Sep 04, 2013 10:15 pm

    It would be nice if he could also test the 6AN8 too, given its use in the other Dyna amps. Dunno if there are any ready-made 6AN8-7199 socket adapters, though.

    Nice find, Bob!

    Jim McShane

    Posts : 154
    Join date : 2011-10-19
    Location : South Suburban Chicago

    Re: Stock Dynaco ST-70 using 7199, 6GH8A and 6U8 tubes - video

    Post by Jim McShane on Thu Sep 05, 2013 8:59 am

    Keep in mind that these tests are not of the tube itself, but how the tube performs in that given circuit. It makes sense that the 6U8 should perform worse in the Dyna circuit since it has the lowest mu triode section and the lowest Gm pentode (compared to the other tubes mentioned). All that translates to lower open loop gain which means less loop NFB - and as a result there is hiigher THD with the 6U8.

    The 6AN8 is getting quite scarce, I suggest it be reserved for the Mk III and such where it was originally fitted. In fact triode-pentode tubes in general are getting hard to come by. There don't seem to be many out there except dribs and drabs.

    tubes4hifi
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    Join date : 2008-11-30

    Re: Stock Dynaco ST-70 using 7199, 6GH8A and 6U8 tubes - video

    Post by tubes4hifi on Sat Sep 07, 2013 7:25 pm

    I've got a box full of 6GH8s that I collected about a dozen years ago, various brands, all used but good condition, anybody want or need any, CHEAP !

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