How to tell.....

Dear tube experts,

How to tell a TFK diamond bottom smooth plate tube is a 12au7 or 12ax7 if most of the letters are missing?

Thanks!

eugeneli10-17-2006 9:15pm

boa2 Details Discussions Posts This discussion Message User 1,551 posts 10-18-2006 at 02:47am Copy Comment URL Report Comment Edit Delete You could listen to the tube. The 12AX7 will have higher gain. Are you sure these tubes are interchangeable without consequence? I thought not, but I could be wrong.