Hi folks! Yesterday my SVP-PRO lost half of its output. It`s not dead silent but can`t compete with drums or guitar anymore. There also appeared slight background noise. Could it be broken tube? I just bought preamp 6 months ago and I thought preamp tubes should last years. I usually prefer overdriven tube sound, so I don`t use –15db patch although I`m using active bass and effects. But the preamp should handle it, shouldn`t it? I`ve been looking for groove tubes for replacement, but they seem to have many sort of 12 ax7 in their catalogue (ax7 M, ax7 C, ax7 R, ax7 R2, ax7 R3) What would be best choice for SVP-PRO? Thanks beforehand!