The A-100 provides a minimum of 90 watts (45 wpc), power output from 4, KT-88's in UL-push/pull operation driven with a direct coupled cathode follower. The cathode follower and voltage amplification stage is directly coupled to form a triple stage combining a variable self-biasing system and a zero voltage control system. The bias system used is an advanced active biasing circuit. This system compensates for fluctuations in bias voltage as supplied to the output stage by detecting cathode current and output level demand. This bias control implementation improves linearity and performance of the output stage by maintaining optimum voltage control. The innovative zero voltage control system stabilizes the cathode follower DC output level to improve operation of directly-coupled circuit components. This occurs in an end to end process from the driver stage to the output stage. Both of these circuits combine to improve the stability and the clarity of the amplifier's output.