A 30W pushpull amplifier based on the 300B direct heated triode output tube. Fully differential driver stage topology, no global feedback, fixed bias amplifier with full voltage regulation. Audio tube complement is a pair of 300B, 6SN7 differential driver stage, and 6SL7 input stage. Topology is long tailed pair. Inputs may be operated in fully balanced or unbalanced mode with no degradation in performance. The power supply features tube regulated B+ and bias supplies. Potential builders should have moderately advanced construction skills, and at least a good DVM for successful construction and debug. Scope and audio generator recommended. This amplifier will drive conventional modern speakers systems quite well. This design was originally featured in a VTV article 10yrs ago.
