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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


3 posters

    What is a SCM?

    WntrMute2
    WntrMute2
    WntrMute2


    Posts : 116
    Join date : 2010-11-21
    • Post n°1

    What is a SCM? Empty What is a SCM?

    Post by WntrMute2 Sat Jul 16, 2011 6:37 pm

    I was thinking about this during my build of my ST-120 and a prior post referred to the SCM. I know what it stands for now, but what does it do? While we are on the subject, what does the Quad Cap do? I know I'm slow at times so forgive my basic questions. Thanks.
    Dave
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    Bob Latino
    Bob Latino
    Bob Latino
    Admin


    Posts : 3277
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°2

    What is a SCM? Empty Re: What is a SCM?

    Post by Bob Latino Sat Jul 16, 2011 8:05 pm

    Hi Dave,

    The "SCM" stands for the Supplementary Cap Module. On the ST-120 an extra 165 uF is added at the point of the quad cap where the two output transformers draw high voltage.

    The quad cap is part of the DC high voltage storage system as is the SCM. The quad cap and the SCM provide "power" to drive the two output transformers on the ST-120. The VTA driver board has it's own "on board" high voltage power storage system. The 4 caps on the back edge of the driver board store power to drive the board. On the original ST-70 the quad cap provided DC power storage for the WHOLE AMP - two output transformers AND the driver board. One of the weaknesses of the original ST-70 was the lack of enough DC power storage to run the amp at higher volume levels. No original ST-70 in stock configuration will ever reach its claimed output of 35 WPC. 25 WPC is a more realistic figure of power for the original ST-70.

    Bob
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    WntrMute2
    WntrMute2
    WntrMute2


    Posts : 116
    Join date : 2010-11-21
    • Post n°3

    What is a SCM? Empty Re: What is a SCM?

    Post by WntrMute2 Sun Jul 17, 2011 9:01 am

    Thanks professor.
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    Westy56
    Westy56
    Westy56


    Posts : 58
    Join date : 2011-05-09
    Location : Albuquerque
    • Post n°4

    What is a SCM? Empty Re: What is a SCM?

    Post by Westy56 Sun Jul 17, 2011 10:11 am

    Bob Latino wrote: No original ST-70 in stock configuration will ever reach its claimed output of 35 WPC. 25 WPC is a more realistic figure of power for the original ST-70.

    Bob

    You could probably get the 35 watts at the expense of astronomical distortion. Wink


    Steve
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    • Post n°5

    What is a SCM? Empty Re: What is a SCM?

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