Inherent Difference - 12AU7 and a 12AT7

Just because the company switched from an au to an at doesn't mean that you can. I'd bet they changed something or determined that more gain was needed and made the modifications. As Hovland before you even consider it.
As far as lasting 1 year, these tubes should last 3000 to 5000 hours. Unless you are leaving it on 24/7, you should get many years out of these. Even if they are wearing out, they shouldn't get noisy so easily. Usually your dynamics will just flatten out?

I'm sure that it is okay to swap between the AU7 and AT7; Hovland confirmed that for me several years ago; when I asked them what the differences were they said 'try it'and let them know what I heard and liked...

I think that I will just buy one of each and find out for myself. I have used the NOS Mullards from Upscale Audio but again these seem to get noisy way to fast. I may contact the Tube Store and get theirs and try something different.

Have anyone tried the outrageously expensive EAT 12AX7's? I am tempted to try them once; wonder if Music Direct would absolutely stand behind them and take them back if I was unhappy with the performance?

And, wonder why EAT does not make an AX7 or AU7?

Stickman as I mentioned they should work without issue but if you go to the web and look at the tube data you will notice significant differences in the voltage and current characteristics of these two tubes.

Kind of like driving a Porsche with a Chevy engine in it. It may work but it's not how it was designed to run it's best. I wouldn't spend a lot of money on nice tubes just to try it. But that's me.

Maybe just get some nice 12au7's like Rodman mention all he said are nice tubes. I have a friend that uses the EAT tubes and really likes them but I am not willing to fork up the money to try them.

The do make a AX7 Music Direct carries them. $225 a pair. That is what my friend owns.