| 摘要 |
PURPOSE: A vacuum tube bias circuit and audio AMP adopting the same is provided to be a new manner different from conventional fixing bias and self bias. CONSTITUTION: An upper constant current circuit(1) generates a constant current by a positive power supply voltage(B+), a lower constant current circuit(2) generates a constant current by a negative power supply voltage(B-). A constant voltage circuit(3) is connected between a current output terminal of the upper constant current circuit and a current output terminal of the lower constant current circuit. An input resistor(Ri) is connected to a position where the constant current circuit and the constant voltage circuit are connected and an AC signal is applied. A bias voltage is applied to a vacuum tube using a voltage dropped through the input resistor based on a difference of current flowing through the constant current circuits.
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