The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    I rebuilt my ST35

    Share

    corndog71

    Posts : 444
    Join date : 2013-03-19
    Location : It can get windy here

    I rebuilt my ST35

    Post by corndog71 on Fri Jun 17, 2016 12:43 pm

    For the 3rd time I rebuilt my ST35 with a custom layout. The previous version used a large box which I needed to fit the big Clarity TC film caps for the power supply. It worked well but took up a lot of space.

    This year my older brother asked me to build him a tube amp for his office. He wanted a small footprint and every connection and control mounted on top so he can drop the amp into a fancy wood box he's going to build for it.

    I went with the Hammond 12x10x2" box and designed a new layout which incorporated Shannon Parks' driver circuit which uses a 12AX7 voltage amp and 12AU7 for phase splitter for both channels. I also used Dave Gillespie's EFB circuit for improved power and lower distortion, a single bias point for each channel, fuses on the EL84 cathodes, that stepped attenuator everyone here likes and finally 2 inputs with 1 pair of RCA and one 1/8" jack. Everything is wired point to point.

    I initially had some trouble due to a missed wire and higher voltages than expected. I think it was a bad regulator in the EFB along with feedback not being properly set. It's all good now. With inputs shorted it is dead quiet. I was surprised by how good it sounded with my cheap test speakers. Pretty cheap to put together too although there was quite a bit of labor.








    daveshel

    Posts : 148
    Join date : 2011-11-06
    Location : Tucson AZ USA

    Re: I rebuilt my ST35

    Post by daveshel on Fri Jun 17, 2016 10:20 pm

    Nice work. Mine is still in the original chassis - stock except for the external EFB board.

    Is it a good idea to have the OPTs that close together?

    corndog71

    Posts : 444
    Join date : 2013-03-19
    Location : It can get windy here

    Re: I rebuilt my ST35

    Post by corndog71 on Fri Jun 17, 2016 10:30 pm

    Rogue Audio does it.


    daveshel

    Posts : 148
    Join date : 2011-11-06
    Location : Tucson AZ USA

    Re: I rebuilt my ST35

    Post by daveshel on Sat Jun 18, 2016 1:49 am

    Well if Rogue Audio jumped off a bridge...

    I was thinking of the layout of the MKIII, where the PT and the OPT are adjacent, but oriented 90 degrees out of phase for polarity. And on the ST-35 and the ST-70, the OPTs were separated. So that gives rise to the question as to whether you might lose separation or gain crosstalk when they abut.

    zx

    Posts : 194
    Join date : 2011-08-05

    Re: I rebuilt my ST35

    Post by zx on Sat Jun 18, 2016 11:57 am

    Nice work like always..bet sounds sweet.....hhscott...Fisher...others set there output trans like you...or you like them......thanks for the pic....






    thanks for the site Bob.........

    Sponsored content

    Re: I rebuilt my ST35

    Post by Sponsored content Today at 6:34 am


      Current date/time is Sun Sep 25, 2016 6:34 am