VTL 2.5 strange behavior

In my VTL 2.5 pre-amp, I've alway wondered why the gain was so high (for years!). I could only turn the volume up a few notches before the volume became very loud. Recently my left channel started to degrade in sound so I purchase tubes for it.

Well, I can now use virtually the whole range of volume on my VTL 2.5. Now I have to turn the pot slightly less than 1/4 up for near field listening. Funny, I was told that the CV4024 had higher gain than the 6350. The thing is that it doesn't sound bad. It almost seems like the gain is a little on the low side or I'm not used to it. Strange very strange.

I looked up gain via search and most stated that it's primarily the circuitry that controls gain. If that is true, what the hell is going on?

Well, if this is how it should be, the thought that I lived with this HIGH GAIN condition for years just kills me! Ignorance is a terrible thing :) Can someone chime in with their thoughts on this!

Went from:
VTL 6350
Mullard 12AU7

Went to:
CV4024 (12AT7) Mullard

Classe CAM200/VTL 2.5/Wadia 301/Linn LP12/Tannoy D700
I think it depends on which unit you have. Mine calls for the 6350's but some of the others have the 12at7's. I accidentally swapped places (12au7/6350) and the gain was super low. Just make sure the tubes are what is called for and they are in the right place.

On my unit, the 12au7's are closest to the front.