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Blue Glow

archie2

archie2

Addicted Member
I have a matched quad of New Issue Mullard EL34s and just noticed there is a blue glow as well as orange. I assume this is normal? I have about 100 hours on them and couldn't be more pleased with the sound. I still have the original vintage Mullard xf2 EL34 quad and these New Issues are a worthy rival.
 
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I worried about this too with a set of soviet 6BQ5 s From the front view of the amp it is hardly noticeable but get around back and to the side and WOW... Blue glow.

I'm into the 2nd year with them and no problems... Used about twice a week for 2-5 hours ata stretch...

Even left the amp on all night once - foolishly...
 
Celt said:
It's a GOOD sign of the tubes having a tight vaccuum.
Click to expand...

Not sure thats entirely true, but this I do know.
With the electrons flowing so quickly inside the tube there are ions which become detached and are deflected by the glass, when they are deflected there is tremedous friction between the ions which causes the blue light to be emitted.
I read this in an RCA Electron tube designers book (1947)some time ago...........
Im glad I read that bit bacuse I always wondered what caused that too...those books are very tough reading but all the same there are parts which are enlighting.....
 
Since I posted I read up on blue glow and ya'll are right, it's normal and has a number of causes. There are 2 types, glow on the inside of the glass envelope and glow inside the plate. My EL34's have a well defined blue glow inside the plate. So as long as the blue glow doesn't change to purple glow or floating pink glow, no problem.
 
Yes, blue is good...

vta09008s.jpg


VTAtubeglow.jpg


-Vic
 
Very cool, now I know why you tube folks like those amps, not only sound good, but look awesome with the lights out!
 
archie2 said:
I have a matched quad of New Issue Mullard EL34s and just noticed there is a blue glow as well as orange. I assume this is normal? I have about 100 hours on them and couldn't be more pleased with the sound. I still have the original vintage Mullard xf2 EL34 quad and these New Issues are a worthy rival.
Click to expand...

A little off subject but I noticed in your signature you have a Sansui 8080db, how do you rate it among your other receivers.
 
thevic24 said:
Yes, blue is good...

vta09008s.jpg


VTAtubeglow.jpg


-Vic
Click to expand...

Dude!! Thats a really nice couple of pictures.....................Evidence that something is actually happening in there, semiconductors are so boaring, they just sit there looking like nothings going on.
 
How come my tubes don't glow that bright? Is it just how you took the picture? Please tell me it is. I cannot afford to replace all my tubes at this moment....
 
davis419b said:
A little off subject but I noticed in your signature you have a Sansui 8080db, how do you rate it among your other receivers.
Click to expand...

This particular 8080DB was "rehabbed" and wood veneered by Merrylander, a first class job. Taking into account cosmetics, function, and sound quality, I would rate it a very, very close third to my Yamaha CR 2020 and Marantz 4270. A lot depends on which speakers with which I match it. It drives the BA A150 speakers with a better sound than the Yamaha but the Yamaha does a better job with the Polks. I had it upstairs at one point driving a pair of Original Large Advents and found that combination produced excellent, tough to beat sound. I rate it very highly overall and the only unit I have that has a clearly superior sound to my ears regardless of speakers is my Altec 345A amp. Hope this helps.
 
can be caused by a mercury droplet thet vaporises, apparently (or so the all knowing web told me).

I was also told (by the same "web") that it can make the tube look internally dirty when not running. Is this true?
 
aussiedan said:
can be caused by a mercury droplet thet vaporises, apparently (or so the all knowing web told me).

I was also told (by the same "web") that it can make the tube look internally dirty when not running. Is this true?
Click to expand...

This only applies to mercury vapor tubes such as an 83. It does NOT apply to typical audio tubes. When a mercury filled tube cools some of the mercury condenses on the glass and gives it a soiled sort of look.

Also - if you want to see what healthy tubes look like, look at Vic's pictures. The orange-ish glow is the tube heaters, the blue glow is fluorescence - and both are 100% normal.

The relative brightness of the orange glow varies from tube to tube - and is not an indicator of tube health unless the tube has no visible glow and is cold to the touch (there are a few tubes that don't glow or heat, but we rarely see them in audio gear). The glow you see in Vic's pictures is NOT the glow you see from a tube passing too much current - "red plating".

These pictures could save a lot of people a lot of time worrying about how bright their tubes "glow", and save others a lot of time having to answer the same question repeatedly. Thanks Vic!
 
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