Abstract: A power supply circuit of a switching inverter type includes a switching circuit including two switching elements capable of being alternately on-off controlled for converting an input from a dc power source into ac by switching of the switching elements and outputting it, a dc output circuit for full-wave rectifying and smoothing a supplied ac input to provide a dc output, a series resonance circuit provided in series to current flowing from the output terminal of the switching circuit, a parallel resonance circuit provided in parallel to voltage produced at the output terminal of the switching circuit, and a switching control circuit for intermittently turning on the switching elements of the switching circuit.

Abstract: A transformer has a secondary winding with an intermediate tap. Two switching elements are connected in series between terminals of the primary winding. A dc power source is connected between a connecting point of the switching elements and the intermediate tap of the primary winding. By turning on and off the switching elements alternately, parallel resonance is produced by primary self inductance and a capacitor provided on the primary side of the transformer. Series resonance is produced by leakage inductance between the primary and secondary sides and a capacitor provided on the secondary side. Turning on of the switching elements at a zero-voltage state and turning off of the switching elements at a zero-current state are realized. Since this transformer is a push-pull type one, currents flowing through the switching elements are reduced to half of a half bridge type transformer.

Abstract: In a remote control signal repeater, which transmits remote control signals from a remote controller to a main device, having a bandpass filter and a level slicer, the bandpass filter is constructed of a parallel LC resonant circuit and a serial LC resonant circuit connected to each other. The resonant frequencies of the respective resonant circuits are set to the substantially same frequency. A resultant resonant characteristic having two peaks on sides of the original resonant frequency of the parallel LC resonant circuit is obtained and resonance of the serial LC resonant circuit is produced between the two peaks, thereby flattening the portion between the two peaks. The level slicer connected to the bandpass filter includes a class-C amplifier which level-slices output of the bandpass filter, a smoothing circuit which smoothes output of the class-C amplifier and a bias control circuit which variably controls the degree of class-C bias in accordance with a smoothed output of the smoothing circuit.

Abstract: An amplification circuit for power amplification of an audio signal or other signal includes a main power source line for supplying a driving power to a load, a switching element inserted in the main power source line for turning on and off the main power line, a smoothing circuit inserted in the main power line for smoothing an output of the switching element, a switching control circuit for switching the switching element with a variable on-off ratio in accordance with the level of an input signal, an auxiliary power source line capable of responding to changes in the level of the input signal at a higher speed than the main power line to supply power to the load, an auxiliary power supply amount adjusting element inserted in the auxiliary power line to adjust the power supply amount from the auxiliary power source line to the load, and an auxiliary power supply amount control circuit for controlling the auxiliary power supply adjusting element to cause power corresponding to any deficiency of power supplie

Abstract: In a power supply circuit, upon turning on of a switching element, a sinusoidal resonance current flows through a series resonance circuit and a smoothing capacitor of a dc output circuit is thereby charged. This resonance current is reversed after a half cycle and a rectifying diode is thereby reversely biased whereby the resonance path is cut off and the resonance current is automatically ceased. While the switching element is on, exciting of an inductance and charging of a capacitor are made in a parallel resonance circuit, though resonance is not made therein. By turning off the switching element in a current zero state thereafter, a parallel resonance by the parallel resonance circuit is started. The switching element is turned on at a timing when voltage of the parallel resonance circuit has returned to a power source voltage.

Abstract: In an acoustic device for custom installation in which one can listen to music in a zone which is different from a zone where an acoustic device main unit, e.g., an audio amplifier or a CD player, is located, turning on or off of loudspeakers is remote-controlled in one zone. An remote control signal from a remote-controller is received by a remote controller signal receiver in that zone and transmitted to a switch control section (microcomputer). The switch control section identifies the particular zone in which the remote control signal has been produced and switches a transmission on/off switch to turn on or off the loudspeakers in that zone.

Abstract: An acoustic apparatus comprises a cabinet, and a loudspeaker unit and a driving apparatus disposed in the cabinet. The acoustic apparatus is driven by an external power amplifier which normally constant-voltage-drives a conventional loudspeaker. The driving apparatus has a power amplifier circuit and a transfer function control circuit, and drives the loudspeaker unit in cooperation with the external power amplifier. The driving apparatus generates an electric energy corresponding to an increase in energy from that which is required in a normal constant-voltage-driving, the increase being produced by an operation of the transfer function control circuit, and the generated energy is inputted to the loudspeaker unit.

Abstract: An adapter is used in combination with a power amplifier in order to apparently change transfer characteristics of the power amplifier when a loudspeaker is driven by the power amplifier. The adapter comprises a first to forth terminal, a connecting circuit and a feedback circuit. The first terminal is connected to a signal source; the second terminal is connected to a signal input terminal of the power amplifier; the third terminal is connected to an output terminal of the power amplifier; and the fourth terminal substantially directly connected to the third terminal and connected to the loudspeaker. The connecting circuit connects the first terminal with the second terminal. The feedback circuit comprises a current detection means for detecting a current flowing through the loudspeaker through the fourth terminal and positively feeding back the current to the input side of the power amplifier through the second terminal.

Abstract: A driving apparatus for driving an electro-acoustic transducer has a main body portion and a control information storage body which is arranged independently of the main body portion and is selectively separated from or coupled to the main body portion, as needed. The control information storage body stores a real circuit or information for setting electrical characteristics of the driving apparatus. In addition, the driving apparatus has a protection circuit for preventing a disadvantageous result of the driving apparatus and a load caused by an unstable operation and the like when the control information storage body is attached/detached to/from the main body portion or when an inappropriate control information storage body is loaded onto the main body portion.

Abstract: A temperature compensation circuit used in a negative impedance driving apparatus such as an amplifier for driving a speaker as a load. A current flowing through the load is detected by a detection element connected to the load, and fed back therefrom, so that negative impedance driving is effected on the load. The detection element is set its temperature coefficient to be equal to or slightly larger than a temperature coefficient of the load, thereby the positive feedback gain is changed upon changing the temperature of the load so that negative impedance driving state is compensated. In another aspect of the invention, a temperature sensitive element or temperature detecting element for sensing or detecting the temperature of the detection element is arranged to change the positive feedback gain and compensate the negative impedance driving state.

Abstract: A driving apparatus for negative-impedance driving a speaker as a load, comprises a detection element, a positive feedback circuit, a temperature compensation circuit, a sensor element, a control circuit, and an input f characteristic control circuit. The resistor as the detection element connected in series with the load detects a current flowing through the load. The feedback circuit feeds back a detection output of the detection element to an input side of the driving apparatus. The temperature compensation circuit controls the negative-impedance driving state to compensate for an increase in load impedance upon an increase in temperature of the load. The sensor element detects that a temperature of the load reaches a predetermined value. The control circuit stops temperature compensation of the temperature compensation circuit or decreases a degree of temperature compensation in accordance with an output from the sensor element.

Abstract: In an impedance compensation circuit of a speaker driving system, an ideal impedance state of the speaker can be equivalently formed by the equivalent impedance means, and is compared with an impedance state of an actual speaker. On the basis of the comparison result, a positive feedback gain in the speaker driving means is controlled. Therefore, even when the internal impedance of the speaker or the impedance of the connecting cable varies, or when the internal impedance of the speaker is changed upon a change in temperature, the motional impedance of the speaker can always be driven and damped with a constant driving impedance. For this reason, in the negative-impedance driving system, an ideal speaker control state can always be realized.

Abstract: A driving apparatus for driving an electro-acoustic transducer comprises a power amplifier for supplying a drive power to the transducer, and a feedback circuit for generating a negative impedance. The feedback circuit has a main body portion connected to the amplifier and a control information storage body for storing control information for setting transmission characteristics of the feedback circuit. The storage body is arranged to be disconnected/connected to the main body portion. The main body portion comprises a plurality of transducer connection terminals connected to a plurality of transducers, respectively, a plurality of relays and normally-open contacts for selectively supplying an amplifier output to the transducer connection terminals. A transducer selection information is housed in the control information storage body.

Abstract: A driving apparatus for electrically driving a vibrator constituting an acoustic apparatus, wherein the output impedance of the driving apparatus is negative at least one frequency associated with the output sound pressure of the acoustic apparatus among resonance frequencies when the acoustic apparatus is viewed from a terminal for driving the vibrator, and the ratio of the output impedance to the internal impedance inherent in the vibrator never becomes constant over all the acoustic reproduction range of the acoustic apparatus. Then, it is possible to eliminate mutual dependency between resonance systems having the resonance frequencies, design of the resonance systems become easy, and improved performance of sound radiation can be expected.

Abstract: A tempeature compensation circuit used in a negative impedance driving apparatus such as an amplifier for driving a speaker as a load. A current flowing through the load is detected by a detection element connected to the load, and fed back therefrom, so that negative impedance driving is effected on the load. The detection element is set its temperature coefficient to be equal to or slightly larger than a temperature coefficient of the load, thereby the positive feedback gain is changed upon changing the temperature of the load so that negative impedance driving state is compensated. In another aspect of the invention, a temperature sensitive element or temperature detecting element for sensing or detecting the temperature of the detection element is arranged to change the positive feedback gain and compensate the negative impedance driving state.

Abstract: An acoustic characteristics changing device includes a frame member disposed in an acoustic energy field, electro-acoustic conversion means attached to the frame member to constitute at least a portion of the device, variable impedance means connected as an electrical load to the electro-acoustic conversion means, and impedance control means for controlling an equivalent impedance of the variable impedance means. The equivalent impedance is variably controlled, so that an acoustic impedance and then its decrease frequency or decrease amount can be electrically, continuously and finely controlled.

Abstract: A DC-to-DC voltage-increasing power source suitable for use in an audio device mounted on an automobile or a portable type audio device includes a DC power source, a drive pulse generation circuit for generating drive pulses which are in 180 degree phase relationship, a switching circuit of a push-pull connection supplied with operating voltage from the DC power source and driven between an on-state and an off-state in response to the drive pulses, a charge and discharge circuit including capacitors charged by being connected in parallel to the DC power source and discharging a sum voltage by being connected in series to the DC power source and an output takeout circuit for taking out this sum voltage as a voltage-increasing DC output. The switching circuit is constructed of voltage-controlled type elements whose on-state is changed in response to the level of an on-pulse in the drive pulses and the drive pulse generation circuit includes a pulse level changing circuit for changing the level of the on-pulse.

Abstract: An analog-to-digital converter suitable for digitalizing signals used in an automatic track finding mechanism of a digital audio tape-recorder. The A/D converter comprises a sampling clock generation circuit for generating a sample clock in synchronism with an input signal and an analog-to-digital conversion circuit for analog-to-digital converting an amplitude peak value of the input signal at a timing of the sampling clock. The A/D converter is samplified in structure, for the sampling clock for sample holding does not have to be quartz oscillated but only needs to be a signal synchronous to the input signals.

Abstract: A dither circuit for improving linearity in A/D or D/A conversion by adding dither to an input signal of an A/D or D/A converter and subtracting dither from an output signal of the A/D or D/A converter. The dither circuit comprises a 1/2 Fs signal generator for generating a 1/2 Fs signal having a frequency which is 1/2 of a sampling frequency Fs, a noise generator for generating random noise in digital form and an adder for adding the 1/2 Fs signal and the random noise together and supplying a resulting sum signal to the adder and subtractor as dither. According to this invention, a conversion error is reduced with a result that the random noise can be of a small level. Thus, high accuracy requirement in a practical circuit construction is reduced so that the circuit construction is easily performed.

Abstract: An amplifying circuit comprises a voltage-current converter for voltage-current converting an input signal to be amplified and a current-current converter including a first transistor (NPN), a second transistor (NPN), a third transistor (PNP) and a fourth transistor (PNP). Emitters of the first and third transistors are connected to each other, collector and base of the second transistor are connected to each other, collector and base of the fourth transistor are connected to each other, emitters of the second and fourth transistors are connected to each other, bases of the first and second transistors are connected to each other and bases of the third and fourth transistors are connected to each other. Output current of the voltage-current converter is supplied to the emitters of the first and third transistors and a constant current is supplied to the second and fourth transistors.