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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

    ST-70 or ST-120 in Kit form

    eminence1963
    eminence1963
    eminence1963


    Posts : 21
    Join date : 2019-06-10
    Age : 61
    • Post n°1

    ST-70 or ST-120 in Kit form Empty ST-70 or ST-120 in Kit form

    Post by eminence1963 Sun Jun 16, 2019 2:03 pm

    Question 1 ST70 or 120 for Hersery 3's? I do like my music loud sometimes. Currently running Prima Luna Dialogue 5 on the 3's. Sounds great low to mid volume, but run it hard and it gives up the ghost starts to scream and music falls apart.
    Question 2 The 120 does not run KT77's reliably or can but shortens the tube life is this true?
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    deepee99
    deepee99
    deepee99


    Posts : 2244
    Join date : 2012-05-23
    Location : Wallace, Idaho
    • Post n°2

    ST-70 or ST-120 in Kit form Empty Re: ST-70 or ST-120 in Kit form

    Post by deepee99 Sun Jun 16, 2019 3:16 pm

    First question to answer your question:
    What's the efficiency of your speaks? I'm guessing being Kliipschs you're at 90 dB or better.
    If >90-91 dB. the ST-70 is all you need to fill a medium-sized concert hall. Another good case for them is their use of 6CA7/EL-34 output tubes, which NOS go for $100-$200 a quad.
    OTOH, the -120, built around the 6550/KT-88, will give you quite a bit more gain but uses the far more expensive KT-88/6550 outputs. (
    Driver tubes are the same for both amps. I use octal 6SN7s in both my ST-70 and ST-120.
    In the purest of all possible worlds, get two ST-70s with a gang of 8 EL-34- 6CA7-type outputs and use them as monoblocks. Those eight good EL-34s will cost you about one-fourth to one-half the price of the Gold Lion KT-88/Tung-Sol 6550 equivalents. Initial expense for the two -70s is higher, but down the road you'll save a fortune in tubes of equal sonic ambrosia.
    Just my thoughts, and I have both of these amps on-line and amply stocked with "pre-blight" outputs.
    Another consideration is your output transformers. The ones Bob uses are superb for the price, but if you're going all-out use Lundahls instead. Another $600 or so, but definitely worth it. I took a flyer on Holger's recommend to do this upgrade and am very glad I did.
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    Bob Latino
    Bob Latino
    Bob Latino
    Admin


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

    ST-70 or ST-120 in Kit form Empty Re: ST-70 or ST-120 in Kit form

    Post by Bob Latino Sun Jun 16, 2019 4:22 pm

    eminence1963 wrote:Question 1 ST70 or 120 for Hersery 3's? I do like my music loud sometimes. Currently running Prima Luna Dialogue 5 on the 3's. Sounds great low to mid volume, but run it hard and it gives up the ghost starts to scream and music falls apart.
    Question 2 The 120 does not run KT77's reliably or can but shortens the tube life is this true?

    The Prima Luna Dialog 5 is a 42 watts per channel amp. If that amount of power does not do it for you, then the 35 WPC VTA ST-70 won't do it for you. I recommend that you use a VTA ST-120 amp in your situation. The 60 WPC from the ST-120 will run your Heresy's up to higher volume levels than the Dialog 5. With the VTA ST-120, I only recommend the use of 6550, KT88 or KT120 output tubes. The Dialog 5 is supposed to be able to also use EL34, KT66, KT77 and 6L6 tubes but these 4 tubes are nearly always used in 35 WPC amps. Yes > If you try to use the EL34, KT66, KT77 and 6L6 tubes in the ST-120, they probably will have a shorter than normal life. They also may not bias properly.

    Bob
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    eminence1963
    eminence1963
    eminence1963


    Posts : 21
    Join date : 2019-06-10
    Age : 61
    • Post n°4

    ST-70 or ST-120 in Kit form Empty Re: ST-70 or ST-120 in Kit form

    Post by eminence1963 Sun Jun 16, 2019 5:43 pm

    Bob Latino wrote:
    eminence1963 wrote:Question 1 ST70 or 120 for Hersery 3's? I do like my music loud sometimes. Currently running Prima Luna Dialogue 5 on the 3's. Sounds great low to mid volume, but run it hard and it gives up the ghost starts to scream and music falls apart.
    Question 2 The 120 does not run KT77's reliably or can but shortens the tube life is this true?

    The Prima Luna Dialog 5 is a 42 watts per channel amp. If that amount of power does not do it for you, then the 35 WPC VTA ST-70 won't do it for you. I recommend that you use a VTA ST-120 amp in your situation. The 60 WPC from the ST-120 will run your Heresy's up to higher volume levels than the Dialog 5. With the VTA ST-120, I only recommend the use of 6550, KT88 or KT120 output tubes. The Dialog 5 is supposed to be able to also use EL34, KT66, KT77 and 6L6 tubes but these 4 tubes are nearly always used in 35 WPC amps. Yes > If you try to use the EL34, KT66, KT77 and 6L6 tubes in the ST-120, they probably will have a shorter than normal life. They also may not bias properly.

    Bob

    Thanks Bob I already ordered up the upgraded coupling caps and attenuator pot upgrade as well already from you this weekend. After reading and searching extensively for my next suitable amp that I can afford It came down to your ST70 ST120. Looks like the 120 is the one I need to buy. That will happen shortly as I waiting for a refund from the amp that I just bought that did not fit my need. If I purchase a amp from you do you sell individual parts for the amp in question. Say I need just a cap or a resistor for instance?
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    Bob Latino
    Bob Latino
    Bob Latino
    Admin


    Posts : 3277
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°5

    ST-70 or ST-120 in Kit form Empty Re: ST-70 or ST-120 in Kit form

    Post by Bob Latino Sun Jun 16, 2019 6:03 pm

    Yes - I keep extra stock of all the parts here for all the VTA amps. You get a 1 year warranty on all the parts in the amp. If you get the tubes from me, there is a (standard tube industry) 90 day warranty on all the tubes.

    Bob
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    • Post n°6

    ST-70 or ST-120 in Kit form Empty Re: ST-70 or ST-120 in Kit form

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