Yeah, it's a neat little setup. Maybe someday I'll pick up a pair of M3's. I still have to go through the box of tubes and other parts Dad had in his office. Hopefully there is some sort of manual in there for the amps. I will need to learn about biasing, etc. At least I think I will. I believe most tubes need to be biased when installed. From the look of the tube boxes, they are as old as the amps. I think he said once he bought the spares from an electronics shop that was closing down. I do remember that my old tube bass amp (Mesa Boogie Bass 400) had like 8 6550 output stage tubes and a few 7ax7 (?) preamp stage tubes. When I got the tubes changed, the bill had "biasing" as a line item. Now I'm sure the output tubes on these aren't anything near a 6550 or even a 6L6 or EL34 (common tubes in guitar amps) but I haven't really looked yet. Just been listening. Hope the spares last a good long time, though. They are Sylvanias, and from past experience with the bass amp I know quality tubes are getting hard to come by. The replacement tubes for my bass amp were "matched" Sovtek tubes. The local amp wizard (every reasonable-sized town has one of these guys who lives on the edge of town in a little house on a bunch of land and seem to know everything there is about every amplifier ever made) said the Sovteks are good tubes but you have to go through them individually to sort out the bad ones then match sets together before installing them. This is due to the legendarily bad QA in Soviet-era factories.
