Marshall 6550 Quad (4) Power Tubes Model VLVE-000Notes Freshly pulled from a 1980s Marshall bass head. Tubes are in very good condition and fully functional. A Marshall 6550 Quad (4) Power Tubes Model VLVE 000 in Very Good condition! At Evolution Music, we attempt to highlight cosmetic defects (if any) by picturing every angle of every piece of gear so you know exactly what you are getting. We always picture any and all accessories too. What you see is what you will get so please check out the