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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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Jim McShane
Bob Latino
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    VTA ST-120 output tubes showing a "blue glow" photo

    Bob Latino
    Bob Latino
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    VTA ST-120 output tubes showing a "blue glow" photo Empty VTA ST-120 output tubes showing a "blue glow" photo

    Post by Bob Latino Sat Dec 08, 2018 1:56 pm

    VTA ST-120 output tubes showing a "blue glow" photo Jeff-Francis-amp-1080

    VTA ST-120 amp with tubes glowing blue ... Certain types of output tubes will emit a violet/blue glow while the amp is playing. This is perfectly normal and does not mean that the tube has a problem or is gassy inside. The blue glow is actually a type of FLUORESCENCE in which the interior of the glass is hit by stray electrons when the tube is on. The glow is easier to see if your listening room is dimly lit. The photo showing the "blue glow" on a matched quad of Sovtek 6550's was taken by VTA amp customer Jeff Francis from California. He used a Pentax 645Z digital camera at F11 with a 6 second exposure @ ASA 1600 with a 60 mm lens. Nice work Jeff ! Beautiful photo !

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    Jim McShane


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    VTA ST-120 output tubes showing a "blue glow" photo Empty Re: VTA ST-120 output tubes showing a "blue glow" photo

    Post by Jim McShane Sat Dec 08, 2018 6:26 pm

    Great picture - thanks for posting it Bob!

    If you look at that photo carefully you can see the most intense blue glow aligns with the holes in the plate and at the top and bottom of the plate structure - where electrons can escape. And as Bob said - when they contact impurities in the glass it can cause fluorescence.

    So the amount of fluorescence varies with both the amount of impurities in the glass AND the number of electrons that can bombard any given area. That's why some tubes show more of it than others.

    One last thing - the impurities in the glass are not a cause of problems or diminished performance, so there's no need to get a case of "audiophile nervosa" over it!
    pedrocols
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    Post by pedrocols Sat Dec 08, 2018 9:09 pm

    So pretty Cool
    vtshopdog
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    Post by vtshopdog Sun Dec 09, 2018 12:16 am

    Kinda purdy....

    (Jim - if you can find a way to test for this you could probably charge more for tubes with “blue glass”  cosmetics - limited, exclusive, special blue electrons with better sound qualities yadda, yadda)
    sKiZo
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    Post by sKiZo Sun Dec 09, 2018 3:23 pm

    VTA ST-120 output tubes showing a "blue glow" photo Big-bottles-lit-003
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    jasn54


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    Post by jasn54 Mon Dec 10, 2018 1:56 pm

    Gold Lion KT88's.  Galaxy S8, no flash. Perhaps the blue would show even more with a longer exposure?

    VTA ST-120 output tubes showing a "blue glow" photo 20181126-155901

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