Unveiled at the 1969 NAMM show in Chicago, Ampeg’s 300-watt SVT (Super Vacuum Tube) bass head weighed in at 95 pounds and contained 14 tubes, six of which were big-bottle 6146 output tubes. To heat all those tubes, massive transformers that generated magnetic fields powerful enough to cause genetic mutations were needed. The amps even came with a warning label: “This amp is capable of delivering sound pressure levels that may cause permanent hearing damage.” And what kind of speakers could handle all that power? Nothing less than two cabinets, each weighing over 100 pounds and packing eight 10-inch speakers. And so began the legend of the SVT, which has set the standard for professional bass amplification for a half century.