Plate power dissipation of EL34-B can reach 30W, whereas EL34A is 25W. EL34-B belongs to tetrode tube compared to pentode tude of EL34A. g1 and g2 of EL34-B is not exactly aligned opposite to each other and it is used in linear power amplification. http://www.AnalogMetric.com 20 Analog Metric Lim.
