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


    ST120 kit auto bias question (new to forum)

    avatar
    grosen

    Posts : 2
    Join date : 2020-05-10

    ST120 kit auto bias question (new to forum) Empty ST120 kit auto bias question (new to forum)

    Post by grosen on Sat May 16, 2020 1:21 pm

    Hello Everyone.  I'm about to buy a VTA ST-120 kit (will do when they're back in stock) and I've been reading the forum in advance to see what people are up to.  It's an amazing resource, so thanks to everyone who contributes.

    My question:  I'm interested in the auto bias board, and would be especially interested if there were version with the auto bias LEDs on the driver board or visible from above.  I see that someone on ebay has a version of this for the ST-70.  (Seller name zpra-72)  My question is whether something like this exists for the St-120.  I know the possibility was discussed on this forum but couldn't tell whether anything came of it.

    I've built kits and can follow directions, but don't want to improvise too much, so I'd be interested in something designed for this purpose.   Is there such a thing?

    (I'd be especially interested in an ST-120 octal board + auto bias board with auto bias LEDs on top.  I have a box of 6SN7s, so I'd be in a position to play around.  But that's a project for another time. I'll build the 12AU7 version first.)

    Thanks!  -- Gideon
    LeGrace
    LeGrace

    Posts : 335
    Join date : 2016-08-07
    Location : Ontario, Canada

    ST120 kit auto bias question (new to forum) Empty Re: ST120 kit auto bias question (new to forum)

    Post by LeGrace on Sat May 16, 2020 4:55 pm

    Current rev of instructions describe how to relocate on board LED`s to a remote location.
    AmpedUp
    AmpedUp

    Posts : 13
    Join date : 2019-10-26
    Location : Kansas City

    ST120 kit auto bias question (new to forum) Empty Re: ST120 kit auto bias question (new to forum)

    Post by AmpedUp on Sun May 17, 2020 1:04 am

    Welcome Gideon. I also am a fan of the AB boards and have them on my M-125s. I researched the best I could before I made this jump and found some good advise in this forum - noted below. I hope that after reading through the thread on point #2 you will see that what you wish to do can be done.
    Pictures for this on a M-125 are posted by jsl234:

    1) Instructions to install on ST-120= [http://www.wop.cz/files/AB-Q_ST-70_ST120_manual.pdf]
    2) Advice for relocating LEDs = [https://dynacotubeaudio.forumotion.com/t3627p100-auto-bias-board-on-roy-s-website?highlight=Auto+bias]
    3) Advice that I took before I purchased was from Dave = Install the AB boards as you are building your amp when the boards are clean and you don't have to relocate and trace wires.
    4) Note: If you install the AB boards before you build and test your amp per the exact instructions that Bob and Roy provide, be sure that you are confident that you are comfortable to troubleshoot yourself. It is not fair to ask them to diagnose any problems when you/we don't follow their exact/well written instructions.
    5) Someone once noted the best thing about the AB boards is that you can just turn on the amps and just "forget about the bias." This is true if you are on the fence about relocating the LEDs.

    Mike
    AmpedUp
    AmpedUp

    Posts : 13
    Join date : 2019-10-26
    Location : Kansas City

    ST120 kit auto bias question (new to forum) Empty Re: ST120 kit auto bias question (new to forum)

    Post by AmpedUp on Sun May 17, 2020 1:09 am

    Correction: jsl1234 did this on his ST-120 - great pics of his VTA amp. The conversation was about doing this on M-125s. Either way this relocation of the LEDs can be done on either amp. Good luck...

    Mike
    avatar
    grosen

    Posts : 2
    Join date : 2020-05-10

    ST120 kit auto bias question (new to forum) Empty Thanks

    Post by grosen on Sun May 17, 2020 11:54 am

    Thanks, all.   I had seen some of that info but not all of it.  I'm going to order the board along with the kit and decide then whether I'm confident enough to install them both at once.  I appreciate the point that I forfeit the right to troubleshooting help if I go off-script.  Given my (lack of) skill, that sounds like a good reason to keep things simple. — Gideon

    Sponsored content

    ST120 kit auto bias question (new to forum) Empty Re: ST120 kit auto bias question (new to forum)

    Post by Sponsored content


      Current date/time is Mon May 25, 2020 7:14 pm