Abstract: An amplification circuit includes a first power supply; a first bipolar transistor whose collector is connected to the first power supply; a first resistor one terminal of which is connected to an emitter of the first bipolar transistor; a second bipolar transistor whose collector is connected to the other terminal of the first resistor; a second power supply; a third bipolar transistor whose collector is connected to the second power supply; a second resistor one terminal of which is connected to an emitter of the third bipolar transistor; and a fourth bipolar transistor whose collector is connected to the other terminal of the second resistor. An emitter of the second bipolar transistor is directly connected to an emitter of the fourth bipolar transistor, thereby becoming an output terminal.

Abstract: An amplification circuit includes a first power supply; a first bipolar transistor whose collector is connected to the first power supply; a first resistor one terminal of which is connected to an emitter of the first bipolar transistor; a second bipolar transistor whose collector is connected to the other terminal of the first resistor; a second power supply; a third bipolar transistor whose collector is connected to the second power supply; a second resistor one terminal of which is connected to an emitter of the third bipolar transistor; and a fourth bipolar transistor whose collector is connected to the other terminal of the second resistor. An emitter of the second bipolar transistor is directly connected to an emitter of the fourth bipolar transistor, thereby becoming an output terminal.

Abstract: A sound signal reproducing apparatus for supplying sound signals of a plurality of channels to speakers via sound amplifier circuits includes: a power supply voltage controller for controlling a power supply voltage to the sound amplifier circuits; a plurality of filter circuits for passing predetermined frequencies of the output signal of each of the sound amplifier circuits in the plurality of channels; a plurality of level detection circuits for detecting levels of output signals of the plurality of filter circuits; an adder circuit for adding output signals of the plurality of level detection circuits; and a comparator circuit for comparing an output signal of the adder circuit with a reference level, so that an output signal of the comparator circuit controls the power supply voltage controller.

Abstract: A sound signal reproducing apparatus for supplying sound signals for a plurality of channels to speakers via sound amplifier circuits includes: power supply voltage control means for controlling power supply voltage to the sound amplifier circuits; a plurality of filter circuits for passing a signal of predetermined frequencies of the output signal of each of the sound amplifier circuits in the plurality of channels; a plurality of level detection circuits for detecting level of output signals of the plurality of filter circuits; an adder circuit for adding together output signals of the plurality of level detection circuits; and a comparator circuit for comparing an output signal of the adder circuit with a reference level, so that an output signal of the comparator circuit controls the power supply voltage control means.

Abstract: Only the standby transformer supplies a current to a control power source while the operation power is off, and supplies a current to a primary power relay when the primary power relay is activated. After activation of the primary power relay, both of the standby transformer and a main transformer supply currents to the control power source and the primary power relay. This makes it possible to reduce the rated current of the standby transformer as well as the standby power.