Eeney meeney miney moe . . .

[peacemaker]

There's a sticker inside my Twin detailing what tubes are supposed to go where. It says that some should be 12AX7, 12AX7A, etc. But all three tubes I looked at (V1, V2, V5) were 7025s. Not what they should be according to the diagram in the amp. Does this matter?

[GuitArtMan]

If I remember my tube lore right a 7025 is a slightly lower gain version of a 12ax7. I wanna say if a 12ax7 had a gain of 100, the 7025 would have a gain of 75 but don't quote me. Anyway, you're perfectly safe using a 7025 where a 12ax7 would go and vice versa.

[212Mavguy]

The 7025 is a 12ax7, same gain, has spiral wound heater filamants that reduce hum in situations where the heaters are driven by AC currents. 5751 is similar to 12ax7 but has 70% gain of 12ax7.

[FrankS]

Here is a link to a chart on The Tube Store website that compares pre-amp tubes gain factors.