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


    ST70 input options to replace stereo/mono switch

    Share

    n3ikq

    Posts : 26
    Join date : 2014-10-16

    ST70 input options to replace stereo/mono switch

    Post by n3ikq on Mon Oct 20, 2014 9:46 am

    I was reading an old article from Frank Van Alstine that recommended replacing the stereo/mono circuitry with a bandwidth limiting filter consisting of a .02uf cap in series with a 10k between the RCA + and the board. Additionally a parallel 475k/1uf combination goes from the board input to ground. Has anyone done this or have any opinions one way or the other? Otherwise I can just stick with the old 470k's center pin to ground. As always, thanks for your time!

    GP49

    Posts : 733
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: ST70 input options to replace stereo/mono switch

    Post by GP49 on Mon Oct 20, 2014 1:38 pm

    Sound Values, later known as Sound Valves, thought it worthwhile enough to copy it in their reissue Stereo 70 (they bought Dynaco's parts stock from Tyco at the shutdown). Panor, in their Dynaco Stereo 70 Series II, also copied it. All the copying was done without the permission of the originator, Frank Van Alstine. Some sources say that Panor subcontracted the manufacture of their Series II to Sound Valves, which would explain a lot.

    If you read comparisons of the Panor (with the bandpass filter) vs the original (without it), be aware that the input/phase inverter tubes are different. Panor used the 6GH8, since they could not source the 7199.

    zx

    Posts : 194
    Join date : 2011-08-05

    Re: ST70 input options to replace stereo/mono switch

    Post by zx on Mon Oct 20, 2014 4:24 pm

    Can you tell me where to find the Articles............. more info on this..Have you done this mod?? Has anyone heard this setup in any Dynaco Amps are other tube amps.......
    .thanks..... for your posting







    Thanks for the Site Bob..............

    n3ikq

    Posts : 26
    Join date : 2014-10-16

    Re: ST70 input options to replace stereo/mono switch

    Post by n3ikq on Mon Oct 20, 2014 5:04 pm

    enjoythemusic.com/magazine/manufacture/0902/

    Sponsored content

    Re: ST70 input options to replace stereo/mono switch

    Post by Sponsored content Today at 7:28 pm


      Current date/time is Sun Dec 04, 2016 7:28 pm