Yamaha Corporation

Nippon Gakki Seizo Kabushiki Kaisha

Masao Noro

Nobuaki H Tsuji

Toshio Maejima

Akira Arai

Akihiko Nozaki

Yasuhiko Sekimoto

Kenichi Yoshinaga

Soichi Takigawa

Kenji Yokoyama

Akira Sogo

Kiyoshi Yamaki

Seiji Hirade

Yasuomi Tanaka

Akihiko Toda

Takahiro Tanaka

Yusuke Yamamoto

Daisuke Suzuki

Takeshi Togawa

Nobukazu Toba

Masamitsu Hirano

Kunihiko Mitsuoka

Yohei Ohtani

Terumitsu Maeno

Yohei Otani

Yuichiro Suenaga

Ryo Kamiya

Kunimasa Muroi

Makoto Kaneko

Masaya Kano

Takayuki Kohdaka

Tatsuya Kishii

Shinya Tamura

Hironari Kawai

Kunito Takahashi

Susumu Ishibashi

Koji Toda

Shoji Yasui

Tsunenori Sano

Eiichi Suzuki

Yoshiki Kasahara

Shin Ito

Yuzo Ishigaki

Takeshi Daishoji

Takanori Shimizu

Kuniaki Morita

Yoshiro Miyake

Hajime Asahira

Masaya Kanoh

Tomonobu Sugimoto

Akihiro Toda

An acoustic apparatus includes a class-D amplifier including a current feedback circuit, and a speaker system including a voice coil driven by the class-D amplifier. The speaker system is configured such that, in a case where the speaker system is driven by an ordinary amplifier having a first output resistance lower than a second output impedance of the class-D amplifier, a Q factor of the speaker system falls below a predetermined lower limit of an ordinary Q factor range of an ordinary speaker system. The current feedback circuit is configured to increase the second output impedance of the class-D amplifier by feeding a current flowing to the voice coil back to an input of the class-D amplifier so as to increase a Q factor as the acoustic apparatus higher than the predetermined lower limit of the ordinary Q factor range and within the ordinary Q factor range.

Acoustic apparatus

In a switching power supply, a rectifying circuit outputs a first voltage. A switching circuit switches the first voltage into a switching voltage. An output circuit generates a second voltage based on the switching voltage. A feedback circuit generates the feedback signal based on the first and second voltages, and includes a carrier wave generation circuit that generates a carrier wave. The carrier wave has a non-linear shape at its rising edge and/or falling edge. A PWM circuit generates a PWM signal based on a comparison between the first voltage and a voltage of the carrier wave. Due to the non-linear shape, as the first voltage is higher, a pulse width of the PWM signal is changeable more greatly based on a change in the first voltage. A low-pass filter generates the feedback signal based on the PWM signal.

Switching power supply

A signal converter includes a magnetic circuit, a diaphragm, a first coil, a second coil, and a variable resistor. The magnetic circuit has a magnetic gap. The diaphragm is disposed over an opening of the magnetic circuit. The first coil is disposed in the magnetic gap and configured to output an electrical signal based on vibration of the diaphragm. The second coil is disposed in the magnetic gap and configured to brake the diaphragm. The variable resistor is connected to a first end and a second end of the second coil and configured to form a closed loop circuit together with the second coil.

Signal converter

Provided is a speaker apparatus including a first speaker having a first surface communicating with an interior and a second surface not communicating with the interior; a second speaker having a first surface communicating with an exterior and a second surface not communicating with the exterior; and a cabinet having boundary surfaces that form an enclosed space. The second surface of the first speaker and the second surface of the second speaker are arranged on the boundary surfaces and are facing the enclosed space.

Speaker apparatus and acoustic system

A speaker controller includes a switch that is inserted on a speaker wiring for supplying a sound signal to a speaker. A switch control circuit can extract and hold an ON/OFF control signal for instructing ON/OFF of the switch from an alternating-current signal supplied via the speaker wiring. A switch control circuit controls ON/OFF of the switch based on the ON/OFF control signal. A power supply circuit can generate a power supply voltage for operating the switch control circuit from the alternating-current signal supplied via the speaker wiring.

Speaker controller, signal supplying device, and speaker system

Provided is an acoustic device with which it is possible to make reproduced sound able to be heard across a wide frequency range, from the front and from the rear. This acoustic device is provided with a flat speakerconfigured to emit sound, from a front and a rear thereof, in a low frequency sound range. Also, provided therein are a first speakerF configured to emit sound, in a direction facing the front of the flat speaker, in a mid-to-high frequency sound range, and a second speakerR configured to emit sound, in a direction facing the rear of the flat speaker, in the mid-to-high frequency sound range.

Acoustic device

Provided is a driving control apparatus that can control relaxation of force in an actuator. The driving control apparatus is provided with: a driving control unit configured to control driving of the actuator according to a driving control signal; and a pressure control unit configured to control, according to a pressure control signal, involvement of the driving control signal in control of pressure to be generated by the actuator.

Driving control apparatus for actuator

A class D amplifier includes a self-oscillating class D amplification circuit that is driven by an output current signal; and a voltage-current converting circuit that outputs an output current signal in response to an input signal voltage and an output signal voltage from a feedback signal voltage.

Class D amplifier

A sensor output device includes a sensor and an output circuit. The sensor includes a piezoelectric element and an output terminal. The piezoelectric element includes porous resin. The output circuit is connected to the output terminal of the sensor and includes a thermistor.

Sensor output device, sound output device, and musical instrument

An electroacoustic transducer includes: a diaphragm having two pairs of longitudinal split tubular surfaces; a converter that performs conversion between vibration of the diaphragm and an electric signal; and a supporter supporting the diaphragm. The two pairs of longitudinal split tubular surfaces form valleys and ridge portions. In each pair of the two pairs of longitudinal split tubular surfaces, one-side portions of the respective longitudinal split tubular surfaces form a valley. Another-side portion of the split tubular surface of each one of the two pairs and an other-side portion of the split tubular surface of the other of the two pairs form a ridge portion. The two pairs of longitudinal split tubular surfaces are arranged in at least one of a state in which the valleys are orthogonal to each other and a state in which the ridge portions are orthogonal to each other.

Electroacoustic transducer

A self-oscillating class D amplifier includes an integration circuit configured to integrate an input signal and output a result of the integration as an integrated signal, a comparator configured to receive the integrated signal at an inverting input terminal and output a pulse width modulation signal by comparing voltages of a non-inverting input terminal being grounded and the inverting input terminal, a switching circuit configured to power-amplify the pulse width modulation signal output from the comparator, a low-pass filter configured to extract an amplified output signal from the power-amplified pulse width modulation signal, a first feedback circuit configured to feed back the output signal of the low-pass filter to the inverting input terminal of the comparator, and a second feedback circuit configured to feed back the output signal of the low-pass filter to the integration circuit.

Self-oscillating class D amplifier

Speaker diaphragm

A power amplifier includes a class-D amplifier and an input signal supplier. The class-D amplifier includes an input portion and a switching device. The switching device is switched according to an input signal that is input to the input portion so that a current is supplied to a load from a power source via the switching device. The input signal supplier supplies the input signal to the input portion of the class-D amplifier, calculates a virtual output voltage to be output from a virtual power source having a prescribed internal impedance characteristic when a current to flow through the load is output from the virtual power source, and adjust an amplitude of the input signal according to the virtual output voltage.

Power amplifier and input signal adjusting method

A power amplifier includes a class D amplification section and a load current feedback circuit. The class D amplification section includes an input section and a switching section serving as an output stage and switched depending on a signal input to the input section, and outputs current from a power source to a load via the switching section. The load current feedback circuit negatively feeds back the current flowing in the load to the input section of the class D amplification section.

Power amplifier

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Hamamatsu, Japan

Masao Noro