The official Western Electric "Blue Glow" in tubes explanation:

[Vortex Joe - N3IBX]

Hello All,
          I found this explanation for the mysterious "blue glow" in tubes from the Western Electric website. Even though the explanation below was for a WE 300B triode, I'm sure it applies to 807's, 1625's and other tubes.

I thought it may be of interest to the AM Community. There seems to be a bit of controversy surrounding the infamous blue glow and this explanation may put it to rest.

Don't throw your 807's or 1625's away just because they have a little blue glow in them!

Regards,
           Joe Cro N3IBX

WE300B Frequently Asked Questions 
Q. I am seeing a blue glow inside my WE300B. Is this bad or a feature?

A. A blue glow may appear in the dome of the WE300B just below the upper mica and the top edge of the plate. The space between the plate and glass is small at this point (less than 1/8 in.) and appears to be the only area of the tube where this phenomenon takes place. The glow is caused by the electrons striking the plate, volatizing the surface, and dislodging atoms of nickel. High speed barium-strontium electrons from the filament collide with the atom, tearing off electrons, ionizing them and causing a deep blue color even in a well evacuated tube. The glow is a function of the plate voltage and the number of gas molecules in the envelope. In a good vacuum there are still billions of molecules. The electrons do not cause trouble because they all return to the positively charged plate. The size of the glow also varies with plate voltage and is not the same for each tube: it can vary from not discernable to very obvious even in daylight. It does not affect tube performance as can be shown by observing the characteristic curves during tube operation.
Dangerous levels of gas will ionize throughout the entire bulb from a high voltage spark. It is pink in color and will cause variations in plate current. Air in the tube will ionize in a similar manner i.e. throughout the entire bulb, but will be more blue than pink. It will oxidize the filament and cause the emission to drop dramatically.
 

[w3jn]

My quad of Reflektor 300Bs in my homebrew stereo amp all do this.... of course rather than the $300 a piece for new WEs they were $8 a piece in Moscow 

[Vortex Joe - N3IBX]

My quad of Reflektor 300Bs in my homebrew stereo amp all do this.... of course rather than the $300 a piece for new WEs they were $8 a piece in Moscow 

John,
      How does your 300B amp sound? Do they put more "snot" than an equal number of 45's? Is your amp in class A?

I've seen Chinese and Rusky 300B's in the $50 range, but $8 each? Holy Cow! That was a bargain. For that price one could build an audio and RF amp out of all 300B's. That would be most FBOM!

Best Regards and hope to BCNU on Saturday!
                 Joe N3IBX

[flintstone mop]

Hi Guys
I heard John's amp while visiting and was shocked at the quality of the audio and it filled with room with undistorted audio. Effecient speakers and a few watts go a long way. I have been impressed by the tube sound.
No need for a high power solid state amp in this house!
Fred

[w3jn]

Thanks for the kind words, Fred 

Yeah, a 300B has a lot more scrote than a 45.  I think a 45 is good for a few watts, a 300B will do 8 watts SE in class A at negligible distortion, mine are running in shove-yank into output trannies from a Heathkit AA-100 (which used 7591s).  Good for about 20-25 watts at < .1% distortion, depending on how they're bi-assed.  I run 'em about 50 mA per tube no signal (I built the thing with a plate current meter).  I have at least a kilohour on this amp and the toobs are still strong.

73 John

[WA1GFZ]

sounds like a little reactor inside an 807. You never see this kind of stuff coming off a FET. 
tubes have the naked lady effect on you while FETs wear a Berka
did I say that....gfz

[Vortex Joe - N3IBX]

tubes have the naked lady effect on you while FETs wear a Berka
....gfz

Frank,
       I positively LOVE that statement and would like your permission to use it. Very very well said!
Joe N3IBX

[Vortex Joe - N3IBX]

Thanks for the kind words, Fred 

Yeah, a 300B has a lot more scrote than a 45.  I think a 45 is good for a few watts, a 300B will do 8 watts SE in class A at negligible distortion, mine are running in shove-yank into output trannies from a Heathkit AA-100 (which used 7591s).  Good for about 20-25 watts at < .1% distortion, depending on how they're bi-assed.  I run 'em about 50 mA per tube no signal (I built the thing with a plate current meter).  I have at least a kilohour on this amp and the toobs are still strong.

73 John

John,
      I thought it was a "no-brainer", that 300B's would deliver quite a bit more skrote than a pair of whimped out 45's in class A. I read somewhere that the two tubes were similar in output and thought the person to be a bit misinformed. Don't get me wrong, there's nothing wrong with 45's, just that 300B's obviously give you a bigger bang for the buck.

I guess you'd compare 300B's to a #50 pube. They develop about the same outpoot in class A, but are just as costly as WE 300B's. 50ma per pube is about the same no siginal cuntrent you'd run an EL34.

Your amp sounds quite interesting, and I like the <1 percent distortion figger. Pretty damn good for a non solid state device! I'd love to hear it sometime.

Not to get off topic here, but tubes do have a certain element of inherint distortion. Solid state devices are largely devoid of this, but offer a rather sanitary sound. I hate to use this "audiophool" word, but your 300B's and other tubes (I'm personally a triode-kinda-guy) have the "tessitura" that solid state devices do not. That's why some mike preamp companies have a 12XA7 in them, to give them a bit of warmth.

Regardz,
           Joe N3IBX

[k4kyv]

A 300B is more like a 2A3 than a 45.  Before  the audiophools latched onto them, a pair or quad of 300B's would make an excellent class-B driver stage.  However, even in the old days they never were that plentiful.  I use a quad of 2A3's in the audio driver stage of my HF-300 rig, at 40 mills per tube, to drive a pair of 810 modulators.

The last time I was at Dayton, the guys selling antique radios at the fleamarket were having to remove the 45 output tubes from broadcast sets and hide them in a safe place to prevent them from getting ripped off.  Evidently, audiophool types were sneaking the AF output tubes right out of the radios.