G9 and tube variations

[aclac]

HI, I started build G9 preamp, and wonder that can I use 12AT7 instead 12AU7 (I have one 12AT7- pair at home)? 12AT7 amplification factor is 60 vs. 12AU7 has 20. Does it need some resistor changes or is it already calculated so that amplification can't go too high? I think, that sound should be almost same, or...

 

[okgb]

In  pinch you could temporaily sub them , but the
12AU7 will have a better " current " drive where it's used in
the circuit so in the long run i believe the performance will
not be as good [ subbing the 12AT ] nd so  , not recommended
It'll work  , just not quite as well
I'm sure someone here can add better detail to this explanation

 

[aclac]

THANKS

I'll get the point and order 12AU7 as planned.