The Dynaco Tube Audio Forum

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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

    St35 or St70

    JCR1234
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    JCR1234
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    • Post n°1

    St35 or St70 Empty St35 or St70

    Post by JCR1234 Fri Feb 18, 2011 7:56 pm

    I am going to build one of these kits. I have never built a hi-fi tube amp, but I have built many guitar amps. I have a couple of questions:

    1. I dont usually listen to music very loudly. I am concerned that I will not be able to get the EL34's in the ST 70 loud enough to get them to their sweet spot. Is there any validity to this concern?

    2. I have lots of guitar amps that use EL84's so I already have lots of NOS on hand. I dont have any access to good NOS EL 34's.

    Aside from the issue if I will be able to take advantage of the EL 34 headroom, is there a difference in sound quality between the two kits?
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    DynakitParts
    DynakitParts
    DynakitParts


    Posts : 215
    Join date : 2008-11-30
    • Post n°2

    St35 or St70 Empty Choosing the right amplifier

    Post by DynakitParts Sat Feb 19, 2011 11:22 am


    Hi,
    Your choice may be subject to the speakers you intend to use with
    either of these amplifiers. Keep in mind that the ST-35 is essentially
    half (17.5wpc) of the ST-70 (35wpc). Accordingly, I would suggest matching
    the ST-35 with a fairly efficient (90+ db) pair of speakers whereas with
    the ST-70 (80+ db)should be fine.
    There is no need to crank up the volume to ear bleeding decibels to
    optimize the sound of either these tube types.

    Regards,

    Kevin @ Dynakit
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    Bob Latino
    Bob Latino
    Bob Latino
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    Posts : 3273
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°3

    St35 or St70 Empty Re: St35 or St70

    Post by Bob Latino Sat Feb 19, 2011 6:50 pm

    I agree with Kevin. The ST-35 is $125 to $150 less expensive but has only half the power of the ST-70. The ST-35 has a few other disadvantages.

    1. The ST-35 has no power switch so unless you want to add a power switch or plug the amp into a switched outlet you will wind up having to plug in and unplug the amp every time you want it on or off.

    2. The ST-35 can only use EL84 output tubes while a modern ST-70 kit can use EL34, 6L6, KT66, KT77, KT88 or 6550 output tubes. Each tube has a slightly different sonic signature and you can tailor the sound to your liking by swapping out different types of output tubes.

    3. In stock form the ST-35 has no adjustable bias system. You really need a matched quad of EL84's in an ST-35. As the tubes wear there is no way to compensate for tube wear by readjusting the bias like on an ST-70. That said, Dynakitparts does have and adjustable bias system for the ST-35 that you can add to any ST-35 to alleviate this issue. See link below.

    Dynakitparts ST-35 bias control kit

    Bob
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    • Post n°4

    St35 or St70 Empty Re: St35 or St70

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