PART 4: Single-Ended Tube Power Amplifier #1

The first single-ended tube power amplifier in this series uses a single triode-power pentode vacuum tube, namely the 6BM8/ECL82 or 11BM8/16A8/PCL82. These vacuum tubes were originally developed for vertical deflection and audio frequency amplifiers in television receivers in the 1950's. They all have the same electrical characteristics except for the heater voltage and current.
The prototype of this project is using the miniature 9-pin 11BM8, a Sylvania new old stock (NOS), due to its affordability. The 11BM8 has a heater voltage of 10.7 volts at 0.45A, whereas the 6BM8 has 6.3 volts at 0.78A. The triode section of the tube is used as a voltage amplifier, while the pentode section functions as a power amplifier.