Question is why do alternate forms of inputs besides the instrument damage the tubes on tube amps? I assume this applies to bass amps as well, but this question is derived from our guitarist saying he didn't know why, but he knew you can't put vocals through his marshall jcm 2000 tube amp. What's causing the damage to these tubes? Second, what about loop pedals and such. Some of those come with factory presets with bass and drums etc on them. Would those damage the tubes as well? I would assume if they did they'd put a warning on the manual but my jamman doens't say anything of that sort (from what i see).