Tube glows bright and then dims?
Nov 22, 2008 at 4:37 PM Thread Starter Post #1 of 6

raekwonse

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I just get a pair of Mullard M8100s for my Little Dot MKIII amp. They sound great, but when I first turn on the amp, the left driver tube glows bright, then dims down to about the same brightness as the right tube. Is this okay? Thanks.
 
Nov 23, 2008 at 10:17 PM Post #5 of 6

fran

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Do a search on inrush current and you'll find out more about it. Its no harm. What happens is that when cold the heater elements in the tubes have very low resistance. Loads of current can flow causing them to heat rapidly (and glow brightly) but as they heat, their resistance rises and so less current can flow - and hence they dim and settle to that level. Try turning off your amp and then turning back on before the tubes cool - they don't glow nearly as bright cos the elements are still hot....


Fran
 
Nov 23, 2008 at 11:01 PM Post #6 of 6

punk_guy182

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Mines do the same also and it has nothing to do with sound imbalancement.

Actually, the right tube glows brigther than dims down to the point where it's a little less bright than the left tube.

I had sound imbalanced and thought the tubes were causing this and after purchasing the Sylvania 5654 with round getters and black plates I realized the problem persisted.

I'll have to do some more testing to see what causes sound imbalancement.
 

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