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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


    Tubes for ST-70

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    brian8599

    Posts : 1
    Join date : 2021-06-06

    Tubes for ST-70 Empty Tubes for ST-70

    Post by brian8599 Sun Jun 06, 2021 5:49 pm

    I am brand new to tubes and my new to me ST-70. I just bought one but it's missing the two front center tubes. I have searched but can't seem to find out what specifically goes in there. What tubes should I use and where would I get them? Does anyone have a diagram of an ST-70 with a layout of the types of tubes necessary for proper functioning? I've come across many posts discussing different tubes (which is great when I'm ready to play). Right now, I'm just trying to get it to work. Thank you.

    Tubes for ST-70 St-70_10
    Earl
    Earl

    Posts : 23
    Join date : 2020-05-10
    Location : Arkansas

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    Post by Earl Sun Jun 06, 2021 7:17 pm

    Check the stickies. Lots of information. Check the internet. Lots of information.
    Dave_in_Va
    Dave_in_Va

    Posts : 405
    Join date : 2013-04-02

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    Post by Dave_in_Va Sun Jun 06, 2021 9:52 pm

    If it's an original Dynaco ST70 the two small tubes are 7199 and you will have to check with tube dealers or get them off eBay.
    I believe you can buy adaptors so you can use an easier to find (and cheaper) tube in those two sockets.
    Bob Latino
    Bob Latino
    Admin

    Posts : 3048
    Join date : 2008-11-26
    Location : Massachusetts

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    Post by Bob Latino Mon Jun 07, 2021 7:24 am

    Yes ... You need a pair of 7199 driver tubes. 7199 tubes are not made any more but you can still find them for sale on Ebay. There is no direct replacement for a 7199 but you can use a 6GH8A tube in those two sockets if you get a 7199 to 6GH8A adapter. You can normally get this adapter from Dynakitparts at the link below but they are presently out of stock on this item. (on 6/7/21)

    7199 to 6GH8A adapter

    Look on Ebay for 7199 tubes ...

    Bob

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    arremondo

    Posts : 2
    Join date : 2021-03-11

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    Post by arremondo Sat Jun 19, 2021 9:18 am

    Since it looks like you still have the original bias pots I would be almost certain that you need (2) 7199 tubes or (2) 6GH8A tubes with adapters. I changed out my driver board to the VTA board that uses more common 12AU7's when I built my kit from 1970 in 2020. I still have the never used Dynaco 7199's from the kit since I switched to the VTA board while assembling it.

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    DavidR
    DavidR

    Posts : 139
    Join date : 2017-08-10
    Location : MetroWest, MA

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    Post by DavidR Sat Jun 19, 2021 10:35 am

    You should look into upgrading the driver board as arremondo did.
    MechEngVic
    MechEngVic

    Posts : 92
    Join date : 2019-01-16

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    Post by MechEngVic Sat Jun 19, 2021 10:41 pm

    If you decide to go with the 6GH8 and adapter route, I recommend the Amperex line of 6GH8's. I've tried the RCA's, Internationals, several Japanese brands, and maybe 6 others that I can't remember. Nothing sounds better than the NOS Amperex. There are 2 maybe 3 versions of the Amperex 6GH8: The French version, the British version, and kind of a Holland version (many times labeled a 6GH8 but really a 6BL8). The British ones are Mullard's and are the best. But any of the three will sound better than any other 6GH8 tube IMO.

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