[irishpatrick33]

I've read the reasons as to why tubes glow blue.

I am trying to get tubes glow blue.... or are more prone to glowing blue.

I am guessing make or type makes a difference.

[lumendog]

I have tung sol kt-66's that phosphoresce blue. They always have. there is still the orange glow to the filaments, but there is a pretty blue haze that also occurs.

[DaveC113]

I have read that SED tubes glow blue because of the metallurgy, I have some =C= el34s that glow blue. My TS re-issue 6550s started glowing blue after a while, which bothers me because glowing tubes can also be caused by a vacuum leak, which is bad and will kill the tube, and maybe damage your equipment. The TS 6550s show some getter wear, not much, but that's also a possible indication of a gassy tube. Maybe others have a bit more detailed explanation?...

[irishpatrick33]

Yes, I am specifically looking for the blue glow. I should have mentioned the tube will be used in a Decware Zbox tube buffer. Which means 12AX7, 12AT7, and12AU7 are the common tubes used. Though you can use others. I was hoping I would be able to find a tube for this that glows blue.

[JoshK]

One way to get blue glow is add mecury rectifiers.