Yamaha Corporation

Nippon Gakki Seizo Kabushiki Kaisha

Shigenobu Kimura

Minoru Ogita

Satoshi Suzuki

Yuichi Nagata

Kiyoto Kuroiwa

Mikio Kitano

Masao Yoshida

Morito Yamada

Masamitsu Yamamura

In an echo effector for imparting an echo effect to an audio signal based on values of a plurality of parameters, a memory is provided for memorizing an interrelationship among the plurality of the parameters which are mutually related to each other. A dial is actuated for independently setting one or more of the parameters to desired values. A microcomputer dependently sets the remaining parameters to appropriate values according to the desired values and the memorized interrelationship. Further, in a sound field effector operative according to a selected program for creating an effect simulative of a sound field in matching with a room situation under which the effector is installed, a program memory stores a plurality of programs which can be selected in terms of types of sound fields and types of room situations. A first switch is operated for designating a desired type of a sound field. A second switch is operated for designating a desired type of a room situation. One program is selected from the program memory according to both of the designated type of the sound field and the designated type of the room situation.

Effector with integral setting of control parameters and adaptive

In an apparatus for amplifying a sound while suppressing a howling noise, a microphone collects a sound and converts the collected sound into a corresponding input signal. An amplifier amplifies the input signal to generate the sound through a loudspeaker. A plurality of equalizers are interposed between the microphone and the amplifier, each equalizer having a variable attenuation frequency for attenuatively filtering the input signal around the attenuation frequency. Detection is conducted for detecting a plurality of noise spectrum peaks of the howling noise contained in the collected sound. Then, an adjustment is conducted adjusting respective variable attenuation frequencies of the plurality of the equalizers correspondingly to the plurality of the detected noise spectrum peaks to thereby remove the howling noise from the generated sound.

Howling remover composed of adjustable equalizers for attenuating

A howling prevention apparatus prevents a howling noise which is generated in a sound amplification system using a microphone and a loudspeaker. The howling prevention apparatus utilizes a plural number of first to n-th equalizers, which have a variable frequency response and which modulate an output of the microphone. A detector detects a frequency point at which a loop gain of the system reaches a peak while supplying a standard noise signal to the loudspeaker to produce a test sound and measuring the sound collected by the microphone through the series of the equalizers. A frequency response of the first equalizer is adjusted to suppress a noise peak at and around a frequency point detected by the detector. Then, a frequency response of the second equalizer is also adjusted to suppress a noise peak at and around another frequency point detected by the detector. Lastly, a frequency response of the n-th equalizer is adjusted by subsequently repeating the above setting procedure.

Howling remover having cascade connected equalizers suppressing multiple

A loudness control circuit for an audio device used in a reproduction circuit for reproducing a music signal recorded on a recording medium comprises one or plural level detection circuits for detecting levels of signal components of low and high frequency regions of a reproduced signal and control circuits for controlling the levels of the signal components of low and high frequency regions of the reproduced signal in response to outputs of the level detection circuits. The level control is made in accordance with a sound-pressure level for each frequency region of a reproduced signal so that an optimum compensation of the level in response to the sound-pressure level becomes possible.

Loudness control circuit for an audio device

A .DELTA..SIGMA. modulation type 1-bit digital-to-analog conversion circuit includes an addition circuit for adding feedback digital data to input multi-bit digital data to provide results of addition, an integration circuit for integrating the results of addition provided by the addition circuit, a quantizer for quantizing output of the integration circuit to provide 1-bit digital data, and a circuit for providing analog data corresponding to the input multi-bit digital data on the basis of the 1-bit digital data. A bit of a predetermined order and bits of orders lower than the predetermined order in the feedback data are respectively made zero and bits of orders higher than the predetermined order only in the feedback data are added by the addition circuit. By feeding back only high order bits of feedback data for addition, the feedback addition is simplified and computation time thereby is shortened.

.DELTA..SIGMA. digital-to-analog converter with bit grouping by

A digital-to-analog conversion circuit capable of preventing a noise produced in a digital system from mixing in an analog output has an input circuit receiving a pulse-code modulated digital signal, a conversion circuit such as a noise shaping circuit for converting the pulse-code modulated digital signal to a pulse wave signal containing analog amplitude information in a time axis direction, a buffer circuit including an electrically insulated coupling circuit such as an optical coupling circuit for transmitting output of the conversion circuit, and an analog output circuit including an analog low-pass filter for delivering out output of the buffer circuit therethrough. A noise generated in a digital system is intercepted by the buffer circuit and is not transmitted further so that mixing of the noise in the analog output circuit is prevented.

Digital-to-analog conversion circuit

A disc playback device capable of automatically adjusting the tone volume of a signal reproduced from a disc comprises a disc identifying circuit for identifying a disc loaded in the device, a tone volume setter for setting the tone volume of a signal reproduced from the disc, a memory for storing tone volume data for each disc set by the tone volume setter together with disc identifying data provided by the disc identifying circuit, and an automatic tone volume adjusting circuit for reading out set tone volume data corresponding to data of the identified disc from the memory when the disc has been loaded in the device and automatically adjusting the tone volume setter to the set tone volume. Data representing an optimum volume for each disc determined by the listener and disc identifying data are stored in the memory. A disc is identified when it has been loaded in the device and the data representing the optimum tone volume corresponding to the identified disc is read out and the tone volume of the reproduced tone signal is controlled in accordance with this optimum tone volume data whereby the tone volume of each disc is automatically adjusted.

Optical disk playback device having automatic volume control

A digital-to-analog converting circuit increases an absolute value of inputted digital data by a bit shift operation when minute digital data are inputted thereto. The shifted digital data are converted into an analog signal, and thereafter, such analog signal is attenuated in accordance with a shift value of the bit shift operation. The bit shift operation and the attenuation operation are performed when the value of the inputted digital data are smaller than a predetermined value for a predetermined time or more. Thus, a conversion accuracy of the minute digital data is raised, and a distortion generation depending on a frequently switching of the bit shift is avoided.

Digital-to-analog converting circuit

A radio receiver comprises a phase locked loop and an automatic frequency control loop which are selectively coupled with a voltage-controlled local oscillator to control a local oscillator frequency. The phase locked loop and the automatic frequency control loop have a common loop filter which supplies the voltage-controlled oscillator with a control voltage. The loop filter is arranged so that its time constant may be switched from a small value to a great value in response to switching of the operation mode of the voltage-controlled oscillator from a phase locked loop control mode for the selection of broadcasting station to an automatic frequency control loop control mode for the maintenance of the local oscillator frequency after tuning of the radio receiver. The radio receiver can be arranged so that the local oscillator frequency may be maintained by the phase locked loop after the tuning of the receiver to a weak broadcast signal when muting control is rendered ineffective by a muting switch.

Radio receiver having phase locked loop and automatic frequency control

A radio receiver comprises a voltage-controlled oscillator acting as a local oscillator, a capacitor to supply a control voltage to the voltage-controlled oscillator, a phase locked loop incorporating the voltage-controlled oscillator and adapted for a preset selection of a broadcast station, a charge/discharge control circuit to charge or discharge the capacitor adapted for automatic or manual selection of a broadcast station, and an automatic frequency control circuit adapted for maintenance of a local oscillator frequency when the broadcast station is received. A control circuit is provided which couples the phase locked loop or charge/discharge control circuit to the capacitor in response to the selection of one of the station select modes and couples the automatic frequency control circuit to the capacitor in response to the reception of the broadcast station in a good receiving condition.

Radio receiver with system for maintaining optimum tuning

A radio receiver comprises a frequency conversion circuit connected between a frequency-variable local oscillator and a divide-by-N programmable counter incorporated in a phase locked loop frequency synthesizer and adapted to continuously change the frequency to be divided by the programmable counter. Owing to the frequency conversion circuit, the local oscillator frequency is permitted to continuously change in the locked state of the phase locked loop so that the intermediate frequency offset adjustment of receivers, that is, the adjustment of the intermediate frequency of each receiver to the center frequency of an intermediate frequency filter used in the receiver can be made easily, and that a reception of such a broadcast station as having a carrier frequency which is not an integral multiple of a channel spacing frequency also can be made.

Radio receiver having phase locked loop frequency synthesizer

A radio receiver comprising a local oscillator, a first counter circuit for computing an algebraic sum of a number corresponding to an oscillating frequency of the local oscillator and a number corresponding to an intermediate frequency, the algebraic sum representing frequency information for a tuned input signal frequency of the receiver, a memory circuit for storing frequency information produced by the counter when the receiver is tuned to a broadcast station in a station search mode, a digital comparator for comparing the frequency information read out of the memory circuit with the frequency information of the counter in a station select mode, and a charge pump and lowpass filter responsive to the digital comparator to control a local oscillator frequency of the local oscillator so that the frequency information of the counter becomes coincident with the frequency information from the memory circuit. A second counter is provided for counting clock pulses in the station search mode. The output signal of the second counter is compared with the output signal of the first counter by the digital comparator. The station frequency information read out of the memory circuit in the station select mode may be programmed in the second counter.

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Hamamatsu, Japan

Shigenobu Kimura