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


    Is this a good PC3 mod?

    Share

    jocoman

    Posts : 1
    Join date : 2014-12-08

    Is this a good PC3 mod?

    Post by jocoman on Mon Dec 08, 2014 11:22 am

    Hi Folks.
    I'm Jim and I am the proud owner of a ST-70 of unknown origins.
    Picked it up from a pawn shop for $200. Plugged it in and it plays.
    Oh yea.
    I think the sound can be improved, so I have been doing a lot of reading.
    I'm looking at the pc3 board and i see someone has done a few mods.
    The .1 have gone to .2ufs and the .05 have got to .1 uf. I think that is all ok.
    However the 82pf have gone!
    Is anyone familiar with the mod. Just go with it or do some more work here?
    Here is a pic.
    http://i59.servimg.com/u/f59/19/08/04/70/modded13.jpg
    Txs everyone.

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: Is this a good PC3 mod?

    Post by tubes4hifi on Mon Dec 08, 2014 11:59 am

    I'm not 100% sure but I think the 82pF in the old original circuit was part of a low-pass filter to insure stability in the amplifier circuit.
    If it's missing I'd put it back in. Of course I can never mention anything about an ST70 without recommending replacing the PCB with our
    VTA70 board, it will improve the sound about 400%.

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