The frame-work of these amplifiers include two fully independent power supplies for the input stage and driver as well as the power section respectively. Either the 6SL7 or 6SN7 for the input section gives great flexibility for gain, and a 6V6GT cathodyne phase-splitter provides high current/high voltage balanced outputs to the power tube grids. The amplifier can use EL34s, KT88s, KT120s and KT150s in Triode or Ultra-Linear mode with variable feedback. Bias switches below the amplifier set the power output and eliminate maintenance as well as having to re-bias the amplifier when the output tubes are switched. In essence, this is the "Universal Push-Pull Amplifier".