12at7 with 12ax7 tubes

The 12AT7 is interchangable with the 12AX7, but has slightly more than 30% less gain. ergo: You will have to turn the volume a bit higher to get the same SPL from your system.

Dropping a 12AT7 in for a 12AX7 does more than reduce gain. The cathode and plate resistors should be changed to make the 12AT7 operate in the most linear fashion. The two tubes have very different transconductance and plate resistance.

"The 12AT7 is interchangable with the 12AX7, but has slightly more than 30% less gain"

Rodman - I've heard that about the 12AX7 vs. the 5751, but never the 12AT7. Are you sure you're on track with this?

Sebrof- I guess I WAS off a bit. the 5751 is 30% reduction in gain. These sites have the difference as 40% less for the 12AT7: (http://thetubestore.com/gainfactor.html) (http://cydathria.com/fdm/12AX7_sub.html) and(to me at least)that seems greater than, "slightly more" of a difference(my bad). Both sites mention that the tubes are interchangable. The first site: that they are, "plate voltage compatible".

My thanks to all. I guess my question then is what Gmuffley is stating. I don't want to change components and don't want any damage to boot. I'll check the links given by Rodman99999 and go from there.