Tokyo Shibaura Denki Kabushiki Kaisha

Hideki Sakano

Shigeru Todokoro

A method of harmonizing the impedances of an audio amplifier and a loudspeaker interconnected therewith, the audio amplifier including a line amplifier and a positive feedback circuit for compensating for the counter electromotive force of the loudspeaker. A voice coil of the loudspeaker is mechanically driven for generating an electric signal at input terminals of the loudspeaker. Then, the amplification degree of the line amplifier or the positive feedback circuit is adjusted to reduce the signal voltage between the input terminals of the loudespeaker to a minimum, during the circulation of the generated signal through the positive feedback circuit and the line amplifier.

Method of harmonizing the impedances of an audio amplifier and

An audio amplifier having an auxiliary terminal for connection of a feedback line to the grounded terminal of a loudspeaker and including a circuit for protection against voltage overload on the amplifier and loudspeaker if the auxiliary terminal is inadvertently connected to the ungrounded terminal of the loudspeaker, or in case of malfunction of the feedback circuit. The protection circuit includes a signal generator activated by the closing of a power switch for producing a check signal for circuiting through the terminals of the loudspeaker to the auxiliary terminal and a controller sensitive to the voltage at the auxiliary terminal for controlling a switch for disconnecting the feedback line, if the voltage at the auxiliary terminal exceeds a predetermined value.

Audio amplifier

An audio amplifier having an auxiliary terminal for connection of a feedback line to the grounded terminal of a loudspeaker and including a circuit for protection against voltage overload on the amplifier and loudspeaker if the auxiliary terminal is inadvertently connected to the ungrounded terminal of the loudspeaker, or in case of malfunction of the feedback circuit. The protection circuit includes a signal generator activated by the closing of a power switch for circuiting a check signal through the terminals of the loudspeaker to the auxiliary terminal and a controller sensitive to the voltage at the auxiliary terminal for controlling a switch for muting the output of the amplifier if the voltage at the auxiliary terminal exceed a predetermined value.

Growing community of inventors

Iwafunemachi, Japan

Hideki Sakano