Trio Kabushiki Kaisha

Eijiro Tamura

A power supply circuit having rectifiers and selectable first to n-th power supply voltage terminals for supplying various levels of output voltages. Between respective terminals and an earth, first smoothing capacitors (e.g. C.sub.1 -C.sub.4) are connected. Between i-th terminal and (i-1)-th terminal (wherein, 2.ltoreq.i.ltoreq.n), second smoothing capacitors (e.g. C.sub.5, C.sub.6, C.sub.n, C.sub.n-1) are connected. When i-th terminal is selected, not only capacitance of the first smoothing capacitor connected between the i-th terminal and the earth, but also capacitance of the first capacitor connected between the (i-1)-th terminal and the earth and the second capacitor connected between the i-th and (i-1)-th terminals are utilized for smoothing operation.

Power supply circuit

In a single-ended push-pull power amplifier circuit having a first transistor of a first driver stage, a second transistor of a first output stage where the first and second transistors are Darlington connected, a third transistor of a second driver stage and a fourth transistor of a second output stage, where the third and fourth transistors are also Darlington connected, first and second resistors are connected between the respective emitters of the first and second transistors and a common output terminal, third and fourth resistors are connected between the respective emitters of the third and fourth transistors and the common output terminal, and a bias circuit for providing a bias voltage of a fixed value between the bases of the first and third transistors, the improvement comprising at least two series circuits of resistors and constant voltage sources for passing the base currents of the second and fourth transistors between (a) the emitter of the first transistor and the emitter of the fourth transistor and (b) the emitter of the third transistor and the emitter of the second transistor respectively.

Power amplifier circuitry

A tone control circuit including an operational amplifier having (a) an input circuit or output circuit and (b) a feedback circuit where circuits (a) and (b) are symmetrically disposed with respect to a reference potential such as ground. Circuitry is also provided to compensate for load and/or feedback impedances. Further, circuitry is provided to reduce the number of switches and capacitors needed to vary the high and low cut-off frequencies of the tone control circuit.

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Tokyo, Japan

Eijiro Tamura