Hi, i have a marshall avt 150 half stack and ive noticed i dont have much gain at all when prac at low volumes in the bedroom, but its better when practicing with my band when its much louder. I was thinking maybe the pre-amp tube needs replacing, as i think there should be more gain than im getting.
Im not sure how long ago it was changed as i bought the amp used a few weeks ago. Think the tube is atleast 8 years old.
I was wondering would an electro-harmonix 12ax7 tube be alright to use? And can somone tell me how to change it as i took the back off the amp but seems a bit inaccessible to reach the tube which taking more components out!
Changing the tube won't increase the gain much I fear. While the AVT has a tube in it's preamp, it's more of a gimmick that helps with advertising than anything.

I don't know how well the AVT reacts to boosters and distortion pedals, that's something I'd try in your place.