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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


2 posters

    VTA70 board mod advantage of increased capacitance

    erniegiro
    erniegiro
    erniegiro


    Posts : 22
    Join date : 2020-08-07
    Location : Atlanta, GA USA
    • Post n°1

    VTA70 board mod advantage of increased capacitance Empty VTA70 board mod advantage of increased capacitance

    Post by erniegiro Sat Oct 17, 2020 12:01 am

    Hi, I want to upgrade my ST70 with the VTA70 board. I notice it comes standard with 188uF on board, and one can upgrade that to 400 uF. What would be the advantage of upping the capacitance?

    At the same time I intend to upgrade the quad cap to the 80+40+30+20uF@525v version. Would upgrade that obviate the need for the additional on board capacitance?

    Thanks in advance for your replies

    Ernie
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    Bob Latino
    Bob Latino
    Bob Latino
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    Posts : 3263
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°2

    VTA70 board mod advantage of increased capacitance Empty Re: VTA70 board mod advantage of increased capacitance

    Post by Bob Latino Sat Oct 17, 2020 7:53 am

    erniegiro wrote:Hi, I want to upgrade my ST70 with the VTA70 board. I notice it comes standard with 188uF on board, and one can upgrade that to 400 uF. What would be the advantage of upping the capacitance?

    At the same time I intend to upgrade the quad cap to the 80+40+30+20uF@525v version. Would upgrade that obviate the need for the additional on board capacitance?

    Thanks in advance for your replies

    Ernie

    Upping the capacitance on the VTA driver board will help if you play the amp at high volume levels. Also, the upgraded 100 uF @ 400 volt caps have a slightly lower ESR rating (equivalent series resistance). This means that these caps will discharge and recharge at a slightly faster rate. This lower ESR is important at higher volume levels. Also > Roy and I use Nichicon caps here which are made in Japan. These Japanese made caps are higher quality than Chinese caps and will last longer.

    On an ST-70 type amp, if you have the VTA driver board with 4 X 100 uF upgraded caps and you also have a new 80+40+30+20 quad cap, that is more than enough capacitance to run the amp at any realistic volume level.

    Bob

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    erniegiro
    erniegiro
    erniegiro


    Posts : 22
    Join date : 2020-08-07
    Location : Atlanta, GA USA
    • Post n°3

    VTA70 board mod advantage of increased capacitance Empty Re: VTA70 board mod advantage of increased capacitance

    Post by erniegiro Sat Oct 17, 2020 10:28 am

    Bob thanks for the fast reply! Makes sense to me.

    Is there advantage of the higher capacitance at lower volume levels when the program material hits a loud dynamic peak?
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    Bob Latino
    Bob Latino
    Bob Latino
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    • Post n°4

    VTA70 board mod advantage of increased capacitance Empty Re: VTA70 board mod advantage of increased capacitance

    Post by Bob Latino Sat Oct 17, 2020 11:12 am

    erniegiro wrote:Bob thanks for the fast reply! Makes sense to me.

    Is there advantage of the higher capacitance at lower volume levels when the program material hits a loud dynamic peak?

    The normal capacitance on the VTA driver board will do fine at normal volume levels and will still be OK for louder dynamic peaks. A key thing here is what is the efficiency of your speakers ? Pushing low efficiency speakers (88 dB and below) requires more power out of the amp and I would always recommend the 4 X 100 uF power cap upgrades with lower efficiency speakers.

    Bob

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    erniegiro
    erniegiro
    erniegiro


    Posts : 22
    Join date : 2020-08-07
    Location : Atlanta, GA USA
    • Post n°5

    VTA70 board mod advantage of increased capacitance Empty Re: VTA70 board mod advantage of increased capacitance

    Post by erniegiro Sat Oct 17, 2020 7:14 pm

    Bob I'll be running the amp on Vandersteen 2CE Signature speakers, 86 db per their specs. I ordered the 400 pf upgrade, thanks for the advice!

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    VTA70 board mod advantage of increased capacitance Empty Re: VTA70 board mod advantage of increased capacitance

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