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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


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    VTA-70 to VTA-120 conversion

    xlr8
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    xlr8


    Posts : 68
    Join date : 2010-02-09
    • Post n°1

    VTA-70 to VTA-120 conversion Empty VTA-70 to VTA-120 conversion

    Post by xlr8 Tue Mar 30, 2010 10:48 am

    Hello,

    Well folks, I have fallen in love with my 2 70's in triode mode. Almost regardless of the music I'm listening to, I find myself switching back to triode mode and leaving the amps alone. The speakers I built are extremely revealing and the difference between triode and pentode modes is VERY apparent. Although sensitive enough for the 70's, I never really thought I'd run them on just over 15 watts. From what I can tell, it seems that upgrading the transformers, adding another choke and some more caps in the power supply and I've got myself a VTA 120? What am I missing? It may be years before I ever do this...
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    wolverine
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    wolverine


    Posts : 59
    Join date : 2010-02-20
    • Post n°2

    VTA-70 to VTA-120 conversion Empty Re: VTA-70 to VTA-120 conversion

    Post by wolverine Tue Mar 30, 2010 1:06 pm

    Same here in respect to triode mode, I have 4 amps and all 4 are now hard wired in triode. For my ears personally, triode mode sounds best no matter what I want to listen to. I use Klipsch Heresey's and KG-4's, I like the horn loaded mids, seems to add more life. Using these speakers and running in triode mode gives me all the sound I could possible want, I don't miss the 60% drop in power one bit myself. A switch to go between triode and pentode to me is simply not needed, I have no inclinations to listen to the pentode mode of the amps.

    wolverine
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    Bob Latino
    Bob Latino
    Bob Latino
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    Posts : 3277
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°3

    VTA-70 to VTA-120 conversion Empty Re: VTA-70 to VTA-120 conversion

    Post by Bob Latino Wed Mar 31, 2010 6:06 am

    xlr8 wrote:Hello,

    Well folks, I have fallen in love with my 2 70's in triode mode. Almost regardless of the music I'm listening to, I find myself switching back to triode mode and leaving the amps alone. The speakers I built are extremely revealing and the difference between triode and pentode modes is VERY apparent. Although sensitive enough for the 70's, I never really thought I'd run them on just over 15 watts. From what I can tell, it seems that upgrading the transformers, adding another choke and some more caps in the power supply and I've got myself a VTA 120? What am I missing? It may be years before I ever do this...

    Hi,

    To change an ST-70 to an ST-120 you need ...

    1. The three transformers from the ST-120
    2. An extra choke
    3. The SCM (Supplementary Cap Module)
    4. A set of ESL (Equivalent Series Induction) caps
    5. Some changes to the components on the VTA driver board

    You would also have to drill four 9/32 inch holes in a stock ST-70 chassis to accomodate the larger output transformers. If you have one of my chassis you wouldn't have to drill the chassis since they are dual drilled for either the ST-70's or the ST-120's output transformers.

    Bob
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    • Post n°4

    VTA-70 to VTA-120 conversion Empty Re: VTA-70 to VTA-120 conversion

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