Yamaha Corporation

Nippon Gakki Seizo Kabushiki Kaisha

Other

Masayuki Iwamatsu

Kenji Yokoyama

Toshio Maejima

Hirotoshi Tsuchiya

A noise reducing circuit includes a variable low-cut filter disposed at an upstream of a sound signal switching section and has a variable cutoff frequency, and a control circuit which controls the cutoff frequency of the variable low-cut filter to a first cutoff frequency lower than a cutoff frequency of a low-cut filter disposed at downstream of the variable low-cut filter when a switching instruction is not issued from a switching instructing section, and increases the cutoff frequency of the variable low-cut filter to a second cutoff frequency higher than the first cutoff frequency when the switching instruction is issued. The switching of the sound signal switching section is executed after a predetermined period elapses since the switching instruction is issued, and the control section decreases the cutoff frequency of the variable low-cut filter to the first cutoff frequency after the switching of the sound signal switching section is completed.

Noise reducing circuit

An acoustic processing device, includes an inputting section which receives a first audio signal and a second audio signal, a first input signal amplifying section which amplifies the first audio signal at an amplification factor, a second input signal amplifying section which amplifies the second audio signal at an amplification factor, a first initial delayed amplifying section, a first adding section which adds the first audio signal amplified by the first amplifying portion and the first audio signal amplified by the first input signal amplifying section, a second adding section which adds the first audio signal amplified by the second amplifying portion and the second audio signal amplified by the second input signal amplifying section, a first supplying section which supplies an audio signal output from the first adding section to a first sound emitting section, and a second supplying section which supplies an audio signal output from the second adding section to a second sound emitting section different from the first sound emitting section.

Acoustic processing device and acoustic processing method

An amplifying apparatus amplifies an input signal supplied to an input terminal and outputs an output signal from an output terminal. The apparatus includes a high-potential power supply line through which a high voltage is supplied; a low-potential power supply line through which a low voltage is supplied; a control unit; and a power supply in which one of the high and low voltages is a fixed voltage, and which generates, as the other of the high and low voltages, one of a first voltage in which a polarity of the fixed voltage is inverted, and a second voltage which is closer to the ground potential than the first voltage is. The control unit controls the power supply to cause the other of the high and low voltages to be switched between the first voltage and the second voltage in accordance with a signal level of the output signal.

Amplifying apparatus

A signal processing circuit includes a waveform shaping section that applies a first gain to an input signal and generates a first signal when an absolute value of a level of the input signal falls within a first input range from a first level to a second level, a variable gain section that adjusts an amplitude of the first signal and amplifies the first signal by a gain to generate an output signal, and a control section that reduces the gain of the variable gain section so that the output signal is prevented from occurrence of clipping when the amplitude of the first signal falls within a second input range. The second input range includes a range of the level of the first signal output from the waveform shaping section corresponding to the first input range of the input signal.

Signal processing circuit

An audio signal supplying device includes a connection terminal which is connected to a speaker unit and which outputs an audio signal to the speaker unit, a specifying section which specifies a type of the speaker unit connected to the connection terminal, an acquiring section which acquires a parameter corresponding to the type of the speaker unit specified by the specifying section from an outside, a storing section which stores the parameter acquired by the acquiring section, an inputting section into which the audio signal is input, an acoustic characteristic controlling section which adjusts an acoustic characteristic of the audio signal input into the inputting section based on the parameter stored in the storing section, and a supplying section which supplies the audio signal whose acoustic characteristic is adjusted by the acoustic characteristic controlling section to the connection terminal.

Audio signal supplying device, parameter providing system, television set, AV system, speaker apparatus, and audio signal supplying method

An amplifier includes: an operation amplifier including a positive input terminal and a negative input terminal; and a detector which detects that a difference between a voltage of the positive input terminal and a voltage of the negative input terminal is equal to or exceeds a predetermined value and outputs a detection signal.

Amplifier

An amplifier includes: a variable gain unit that adjusts an amplitude of an input signal and outputs a first signal; an amplitude limiting unit that limits an amplitude of the first signal and outputs a second signal set to have an amplitude of a first amplitude value or less; an amplifying unit that amplifies the second signal to output the amplified second signal as an output signal; and a control unit that detects when the first signal has an amplitude of a second amplitude value or more to control a gain of the variable gain unit so that the amplitude of the first signal becomes less than the second amplitude value, the second amplitude value being larger than the first amplitude value.

The amplifier comprises an inverting negative feedback amplifier circuit using an operational amplifier, a comparator for comparing the potential of the negative phase input terminal of the operational amplifier with the reference potential Vref of the comparator, and a low-pass filter. The imaginary short state of the operational amplifier is lost when clipping occurs on the output signal. It is thus possible to detect clipping by monitoring the potential of the negative phase input terminal.

A class D amplifier includes: an amplifier that generates a digital signal for driving a load based on an input signal; an attenuator that attenuates the input signal according to an attenuation command signal; and a clip prevention controller that outputs the attenuation command signal to intermittently attenuate the input signal when the digital signal is brought into a clip state or a near-clip state.

Class D amplifier

On the basis of localization control data, a sound image localization controlling circuit reproduces input audio signals via a plurality of speakers after having applied predetermined delay-involving signal processing to the audio signals, to thereby perform sound image localization processing to localize sound images of direct sounds in a desired range including an area outside a space surrounded by the speakers. The audio signals are also supplied to a sound field controlling circuit after having been delayed by a predetermined time. The sound field controlling circuit performs operations to convolute the audio signals with reflected sound parameters so as to generate reflected sounds. The output signals of the sound image localization controlling circuit and sound field controlling circuit are fed to adders each adding together the signals of same channel. The resultant added signals are then sent to the speakers in a listening room for audible reproduction.

Sound image and sound field controlling device

A sound field control device includes a surround decoder for decoding an input surround encode signal and generating three channel signals of L, C and R to be reproduced in front left, front center and front right and one channel signal of S to be reproduced in the rear, output terminals for outputting the three channel signals, a first reflected sound generation section generating a reflected sound of the signal S, a second reflected sound generation section generating another reflected sound signal of the signal S, a first adder adding the reflected sound signal generated by the first reflected sound generation section and the signal S together, a phase shifting section shifting phase of the reflected sound signal generated by the second reflected sound generation section according to frequency of the reflected sound signal, a second adder adding a reflected sound signal provided by the phase shifting section and the signal S together, and output terminals for outputting signals of RL and RR channels for reproduction in rear left and rear right positions or reverse positions. At least one of the first and second adders adds the reflected sound signal and the signal S together at a rate at which a value obtained by dividing level of the reflected sound signal by level of the signal S will become 0.5 or over.

Sound field control device

An AC-3 decoder output signals of five channels, i.e., main signals of left front, center front and right front channels and surround signals of two channels. A first synthesizing section synthesizes the three-channel main signals and a difference signal between the two-channel surround signals, and the resultant synthesized signals are then fed to a main sound field signal forming section which in turn forms main sound field signals. A second synthesizing section synthesizes the surround signals of the two channels and a difference signal between the main signals of the left and right channels, and the resultant synthesized signals are fed to a surround sound field signal forming section which in turn forms surround sound field signals. A composite sound field forming section synthesizes the main sound field signals, surround sound field signals and original surround signals so as to form composite sound field signals. The main signals of the three channels are reproduced via a set of left-, center- and right-front speakers, and composite sound field signals are reproduced via another set of left- and right-front speakers and left- and right-rear speakers.

Sound field controlling device

A sound field control device for reproducing plural reflected sound signals of a source signal about a listening point includes a reflected sound signal generation section for generating reflected sound signals to be sounded at front left and front right positions of the listening point and a reflected sound signal to be sounded at a rear position of the listening point, a phase shifting circuit for phase shifting the reflected sound signal to be sounded at a rear position and thereby producing a first phase shifted signal and a second phase shifted signal which are different in phase substantially by 180 degrees from each other, a first adder for adding the reflected sound signal to be sounded at a front left position and the first phase shifted signal together, and a second adder for adding the reflected sound signal to be sounded at a front right position and the second phase shifted signal together. Outputs of the first adder and the second adder are used for driving loudspeakers disposed at front left and front right positions of the listening point. A stereophonic sound field rich in presence can be created with only two loudspeakers without using four loudspeakers as in a prior art device.

An input level adjusting circuit used for an input source switching section in an audio device such as a control amplifier comprises an input selector for selecting one of input signals from plural input sources and outputting the selected signal and also outputting information concerning the selected input signal, a level adjusting circuit connected to this input selector for adjusting the level of the selected input signal, a memory for prestoring input level setting offset amounts which are relative differences in an amount of level adjustment for the plural input sources, and a control circuit responsive to the information concerning the selected input signal applied from the input selector for reading out one of the input level setting offset amounts for the corresponding input source and controlling the level adjusting circuit in accordance with the read out input level setting offset amount. The level adjusting circuit is automatically controlled in response to the selection of the input source to adjust the level of the input signal and thereby maintain a constant output level regardless of difference in the input level.

Input level adjusting circuit

A control circuit for controlling reproduced tone characteristics capable of prestoring sound field characteristics to be imparted to a reproduced tone and frequency characteristics of the reproduced tone in combination and reproducing these characteristics simultaneously comprises a sound field characteristics imparting circuit responsive to an input tone signal for producing a sound field effect signal thereby to impart sound field characteristics to a reproduced tone, a frequency characteristics control circuit receiving the input tone signal and outputting the same after controlling frequency characteristics thereof, a memory for storing parameters for setting sound field characteristics to be imparted to the reproduced tone and parameters for controlling frequency characteristics of the input tone signal in combination, and a control circuit for reading out the parameters for setting sound field characteristics and the parameters for controlling frequency characteristics of the input tone signal simultaneously and controlling the sound field characteristics imparting circuit and the frequency characteristics control circuit with the read out parameters to reproduce a sound field.

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Hamamatsu, Japan

Masayuki Iwamatsu