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    VTA ST70 ΚΤ120 tubes

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    kost

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    VTA ST70 ΚΤ120 tubes

    Post by kost on Mon Nov 18, 2013 9:32 am

    Hi

    Is it risky to use the KT120 tubes in my VTA 70 with upgraded transformer?

    thank you

    Bob Latino
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    Re: VTA ST70 ΚΤ120 tubes

    Post by Bob Latino on Mon Nov 18, 2013 9:57 am

    Kost,

    I don't think it is a good idea to use the Tung-Sol KT120 output tubes in a VTA ST-70. You can use KT88 output tubes in a VTA ST-70 but KT120 output tubes will draw even more current than a KT88. At the very least the amp will run noticeably warmer.

    The VTA ST-120, however, has a larger and heavier duty transformer than the VTA ST-70 and you can use the Tung-Sol KT120 output tubes in a VTA ST-120.

    Bob

    arledgsc

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    Re: VTA ST70 ΚΤ120 tubes

    Post by arledgsc on Wed Nov 20, 2013 4:28 pm

    For an EL34 replacement look into the Gold Lion KT77s.  Love them in my 50W Marshall clone amp.  They can though be bright and open on top which is the opposite in my experience with KT120s in the ST-120.  Bass and midrange really good.  But much better clarity than EL34 IMHO.

    deluxmon

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    Re: VTA ST70 ΚΤ120 tubes

    Post by deluxmon on Wed Nov 05, 2014 9:10 am

    Picking up on this old thread.......Bob, will running a KT120 in a VTA ST-70 do any harm or just run hotter and perhaps not take real advantage of what the KT120 can do?  Additionally, is it possible to simply put a ST-120 transformer on a ST-70?

    Bob Latino wrote:

    Mike Matthews of New Sensor has just announced that they will soon be carrying the new Tungsol KT120 tube. The tube is not as yet on their web site but a description of the tube sent to me by New Sensor is below. This tube is plug compatible with a KT88 or 6550 tube. They released some dealer prices to me but figure a retail price in the $45 price range per tube. (Retail prices are now posted on the New Sensor web site with a mid May delivery date)

    [i]"March 25, 2010


    This tube should work fine in any Dynaco Mark III or VTA ST-120. It could also be used with any Dynaco ST-70 or Mark IV as long as you have an upgraded power transformer.


    Bob

    Specifications for this tube > http://www.newsensor.com/releases/KT120TungSol.pdf

    Curves for this tube > http://www.newsensor.com/releases/KT120TungSol-Curves.pdf


    Last edited by deluxmon on Wed Nov 05, 2014 9:15 am; edited 1 time in total (Reason for editing : adding Bob's Quote from 2010)

    Bob Latino
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    Re: VTA ST70 ΚΤ120 tubes

    Post by Bob Latino on Wed Nov 05, 2014 4:57 pm

    I don't recommend the use of the Tung-Sol KT120 output tubes in the VTA ST-70 or the original Dynaco ST-70. KT120 tubes draw more current than KT88 or 6550 output tubes and will stress out the transformer more than a KT88 or 6550 output tube. KT88 or 6550 output tubes are fine to use in the VTA ST-70 but not (IMHO) in a stock Dynaco ST-70.

    Note - KT120 output tube are fine to use in either the VTA ST-120 or the VTA M-125 monoblocks. The power transformer in the latter two amps mentioned has heavier duty wiring and a much higher stack to dissipate the heat better.

    Bob

    deepee99

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    Not to change the subject, but ...

    Post by deepee99 on Thu Nov 06, 2014 8:35 pm

    . . . Has anybody tried the KT-150s yet?

    Bob Latino
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    Re: VTA ST70 ΚΤ120 tubes

    Post by Bob Latino on Thu Nov 06, 2014 11:00 pm

    David,

    I have had one customer use the Tung-Sol KT150 output tubes in a VTA ST-120. He reported that they worked fine and sounded good biased like a KT88. IMHO they will probably offer nothing more in sound quality over the Tung-Sol KT120. They also cost about double the price of KT120 tubes ($90 to $100 for EACH KT150) ..

    Bob

    deepee99

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    Re: VTA ST70 ΚΤ120 tubes

    Post by deepee99 on Thu Nov 06, 2014 11:35 pm

    Bob Latino wrote:David,

    I have had one customer use the Tung-Sol KT150 output tubes in a VTA ST-120. He reported that they worked fine and sounded good biased like a KT88. IMHO they will probably offer nothing more in sound quality over the Tung-Sol KT120. They also cost about double the price of KT120 tubes ($90 to $100 for EACH KT150) ..

    Bob

    Good Lord! For that much cabbage you can get a New Jersey NOS Tung-Sol 6550, back the bias down a bit, and live forever.

    bluerondo

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    Re: VTA ST70 ΚΤ120 tubes

    Post by bluerondo on Thu Nov 20, 2014 11:13 pm

    I just put in some KT88, Electro-Harmonix in my VTA ST70 and they sound really great to me. They look awesome also...About $114.00 for the quad.

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