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ACME 300B matched pair - different blue glow intensity - new in amp world

Hi, I bought new pair matched ACME 300B. 

Everything is perfect, but between tubes there is small difference in blue glow intensity (photo in attachment). Amp socket swap, doesn't change that. One is brighter that second one.

I know the basics (from where is this effect and why), but I don't have a practice..

Due tubes where quite expensive, I just wanna be sure that everything its fine, or this difference in blue glow intensity, mean something that I should worry about ?

Thanks for help

https://postimg.cc/gallery/dT5SNg0

wiaderko
ghdprentice
6,966 posts
 

So, I believe what the photos show is that one tube has the blue glow and one doesn’t and the tube that glows switches sockets… showing it is a characteristic of the tube and not the amp.

 

Yes, I would be concerned. Whenever, I have detected a difference in the look of a tube it has indicated something wrong. While it has not happened often. 
 

I would contact the dealer you bought them from. There has to be a difference in vacuum or the components inside or something. I do not consider myself a tube “expert”, although I run 40+ tubes and have used them in one or more components for well over 20 years.

wiaderko OP
2 posts
 

So, I believe what the photos show is that one tube has the blue glow and one doesn’t and the tube that glows switches sockets… showing it is a characteristic of the tube and not the amp.

yes, exacly. I swapped them to check that is not socket issue.

I will ask the dealer. Thank you.

If anybody would like to add a penny, you are welcome

dekay's avatar
dekay
5,559 posts
 

I've experienced the blue glow (floating on the glass) on numerous 300B tubes to varying degrees and never found a correlation between such VS sound quality or longevity.

The only high failure rate 300B's I used were from Svetlana St. Petersburg, though I did have one pair make it beyond 600 hours of usage while still testing as new.

The blue glow, to varying degrees, was evident in 300B's from China, Russia, Eastern Europe and 2 pairs of WE's manufactured well before the late 90's.

The color I did see prior to failure was increased amber/orange, but it was internal from the grid wires and it did not coat (float on) the glass envelope like the blue did.

What was interesting about the "failing" Svetlana's was that if they did not completely fail they still worked (sounded fine) at much lower SLP's (even though maybe half of the grid wires were glowing/operational).

Testing them on a tube tester @ that point (TV7/539C) would put them out of their misery.

This said, I agree with ghd's advice as they are new tubes form a vendor.

 

DeKay

 

 

 

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