Just wondering where new tubes should be biased at and what brands do people like? Bought a demo model from sweetwater and it did not come with the manual. Also had a problem the lead channel would not work and boost function did not work. Light would come on when switching channels but no sound and clean was perfect. Tried different preamp tubes and could hear a faint sound and static while turning knobs. After a while I realised that mashing on top of cabinet it would cut in. So screwed in the chassis bolts as they were loose! Thought it was working but nope. Scratched head and loosened a bit and found the chasis bolt closest to lead channel if touched with screw driver or finger the channel would work. Took chasis out and everything looked beautiful! Looked at cabinet and part of the foil tape was bent over so layed the tape flat with a finger and bolted it back in and everything works fine. I am guessing that ground/sheilding was necessary to completely switch into the lead channel. The boist also worked after that. Anyone have an idea about that? Debating whether I should keep it as I paid too much if it is going to be troublesome. Played it loud and for 2 hours after fixing so probably be fine. Either way love to hear your opinions.