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
Bob Latino
6 posters
VTA ST-120 output tubes showing a "blue glow" photo
Bob Latino- Admin
- Posts : 3271
Join date : 2008-11-26
Location : Massachusetts
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 !
edman44 likes this post
Jim McShane- Posts : 237
Join date : 2011-10-19
Location : South Suburban Chicago
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!
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- Posts : 162
Join date : 2014-11-24
Location : Western MA
So pretty
vtshopdog- Posts : 155
Join date : 2015-07-11
Location : UT, USA
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)
(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- Posts : 1530
Join date : 2013-04-01
Location : Michigan USA
jasn54- Posts : 51
Join date : 2015-04-13
Gold Lion KT88's. Galaxy S8, no flash. Perhaps the blue would show even more with a longer exposure?
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