Hi all, very new to tube swapping so doing a load of reading. I have a MkV:25 which has a 12AX7 in V6/Driver/Phase Inverter spot. Have any of you guys any opinions/joys/horror stories with replacing the 12AX7 with a 12AT7 in the V6 spot? Just looking for some guidance before I splash out on replacement/backup tubes. Thanks Guys.