So a while back I had a problem with my MT-15 but then fixed with with new pre amp tubes. Thought it was going to be okay to play cranked at my friends house again but when I did bring it over it couldnt even play cranked but it was playing all volumes just fine at my house. Now it seems to be stuck on one setting of volume and wont turn up any louder whatever position the volume knob is at. All tube have been replaced too and the problem still persists. Anyone have any idea on what i can do or what the fix is for this.