Re: Changing the Tube of an Vox AD15?
I've tried 3 different tubes in mine, and while in some ways they improve things, overall, I've yet to find anything better than the stock EH tube.
The GT 12ax7Cs, Mesa 12ax7, and the Sovtek 12ax7 I've tried have resulted in a entirely too tight/compressed tone and a loss in playing dynamics. The gain is increasdd quite a bit, and the amp gets darker and less 3 dimensional. I can see why these would work great in the pre-amp of a real tube amplifier, but IME they are a poor choice in the Vox modeller.
A speaker change will def improve things..especially on the 30W ADT which is by far the worst sounding of the ADT amps. Stick with the 8" or 12" speaker versions.