[dsavitsk]

Saw your note in the blog.  You probably don't want to use it. I use them in a spud headphone amp, and think it's a great tube, but any vibration at all (even turning off the power switch) leads to a tiiiiiiiiiiiiiinnnnnnnnnggggggggg that takes a long time to go away.  Oh, and they cost a mint and are beasts to keep from oscillating. Great for one off DIY, but probably not for commercial or kits. Ditto for 6688, which is too bad as it is cheap and good sounding.  6c45 is cheaper, less prone to oscillation, easier to get, and doesn't tiiiiiiiiiiiiiinnnnnnnggggggg.

[JohnR]

I haven't been following the blog, I wish Jim would post his thoughts here. Nonetheless, my experience with headphone amps (several years ago now) is that you don't want a lot of gain. Can a headphone amp be made out of something like a 12B4? (Just wondering out loud....)

[hagtech]

Can a headphone amp be made out of something like a 12B4?

Probably, but it will need an extra gain stage.  I'm using the 6H30 for my headphone amp.  Everything worked out just right for the topology I chose.

You probably don't want to use it [7788]

This is a tube I've never played with before.  It comes recommended by a friend, who actually suggested using it for a phonostage front end, where microphony is a bad thing.  I hate that "ting" thing.  Thanks for the tip.  I will look at 6C45 as an alternate.  I'm not too worried about the instability, as RF is one of my non-audio specialties.  But microphonics drives me nuts.

jh