Abstract: An acoustic apparatus comprising a resonator having a resonance radiation unit for radiating an acoustic wave by resonance, a vibrator arranged in the resonator, and a vibrator drive means for driving the vibrator. The vibrator has a diaphragm having a direct radiator portion for directly radiating an acoustic wave, and a resonator driver portion for driving the resonator. The vibrator drive means has a drive control means for controlling the drive condition so as to equivalently reduce or invalidate the internal impedance inherent to the vibrator.

Abstract: Disclosed is a damping member comprising, as main components, a petroleum resin, asphalt and mica. By selecting and using mica as the filler and incorporating mica in an amount smaller than the amount of asphalt, the adhesion follow-up property to a substrate can be improved.This damping material can be attached simply and assuredly to a substrate having a curved surface, such as a tube or pipe, an air-conditioning duct or a part of a building or vehicle by heat-pressing or heat-fusion-bonding, and a product having an excellent damping effect is provided.

Abstract: Method for observation of vibration mode in which a substance inclusive of structures and materials to be observed in vibration mode is vibrated, heat generated by giving vibration is held at the vibrating parts, infrared emission energy emitted from the substance is optically detected to visually display the distribution of temperature change at each vibrating part as thermal imagery.

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: In a magnetic recording medium wherein a metal thin film magnetic layer and a topcoat layer of an organic fluorine compound are formed on a nonmagnetic substrate, the surface of the magnetic layer is plasma treated or plasma oxidized, enhancing the bond between the adjoining layers. A protective film of carbon may be disposed between the magnetic layer and the topcoat, with the surface of the protective carbon film plasma treated. Instead, a protective film of plasma-polymerized organometallic compound may be used.

Abstract: In a magnetic recording medium wherein a metal thin film magnetic layer and an overcoat are formed on a nonmagnetic substrate, durability is improved when the overcoat comprises a plasma-polymerized film and a topcoat of an organic fluorine compound; a plasma-polymerized film, a protective carbon film, and a topcoat of an organic fluorine compound; a plasma-polymerized film containing C, F and H; or a plasma-polymerized organometallic film and a fluorine or silicon-containing topcoat. Oxidation of the upper surface of the magnetic layer with a plasma is also effective.

Abstract: In a magnetic recording medium wherein a metal thin film magnetic layer, a protective film or carbon, and a topcoat layer are formed on a rigid substrate in this order, the topcoat layer is from an organic fluorine compound by gas phase deposition.

Abstract: A sample hold circuit consists of a variable gain voltage-to-current converter and an integration circuit which are connected in series. The conversion gain of the variable gain voltage-to-current converter varies in response to a level of a sampling pulse and one of a follow mode and a hold mode is selected in response to the level of the sampling pulse. In the follow mode when the level of the sampling pulse is high, the conversion gain of the converter is set to the maximum and an output signal of the integration circuit follows up an analog input signal which is inputted into the converter. In the hold mode when the level of the sampling pulse is low, the conversion gain of the converter is set to the minimum and the level of the output signal of the integration circuit is held at a level just before the hold mode is selected.

Abstract: A power amplifier circuit with less harmonic distortion factor and with remarkably high slew rate consists of a drive amplifier, an output amplifier, a distortion cancellation circuit, a negative feedback loop and a primary amplifier. The output amplifier having an impedance load is driven by the drive amplifier and performs the push-pull amplifier operation. The distortion cancellation circuit drives the impedance load with a voltage gain of "1", whereby the distortion cancellation circuit cancels the distortion included in the output voltage of the output amplifier based on the voltage difference between the input and output voltages of the output amplifier. Hence, the apparent gain of the output amplifier is infinite. The negative feedback loop feeds the output voltage back to the primary amplifier as a negative feedback voltage. The primary amplifier drives the drive amplifier based on the voltage difference between the arbitrary input voltage and the negative feedback voltage.

Abstract: A gain-controlled amplifier amplifies an input signal at a gain which varies exponentially in accordance with a control voltage applied thereto and selectively outputs one of non-inverted and inverted output signals substantially identical in characteristic with each other. The gain-controlled amplifier comprises first and second transistor pairs, a common emittor driving circuit and a subtracting circuit. The first transistor pair comprises first and second transistors, and the second transistor pair comprises third and fourth transistors. The emittors of each of the transistor pairs are joined together, and bases of the first and third transistors and bases of second and fourth transistors are joined together, respectively. The two sets of joined bases serve as input terminals of the control voltage. The common emitter driving circuit complementalily drives each of the joined emitters in accordance with the input signal of the amplifier.

Abstract: A gain-controlled amplifier amplifies with reduced distortion an input signal at a gain which varies exponentially in accordance with a control voltage, and has a wide dynamic range irrespectively of the value of the control voltage. The gain-controlled amplifier comprises first and second operational amplifiers, first and second transistor pairs, a bias current control circuit and a subtracting circuit. The first transistor pair comprises emitter-coupled first and second transistors of the same conduction type (PNP or NPN), and the second transistor pair comprises emitter-coupled third and fourth transistors of the same conduction type as the first and second transistors. The common emitters of the first and second transistor pairs are connected to output terminals of the first and second operational amplifiers, respectively. Non-inverting input terminals of the first and second operational amplifiers are grounded.

Abstract: A device for forming a stereophonic sound field in a simulated fashion constructed in the form of a monophonic-to-stereophonic conversion circuit in which a monophonic signal is applied to cascade-connected twin-T circuits having different null point frequencies and an output signal of the twin-T circuits is provided as one stereophonic channel signal whereas an output obtained by substracting the one stereophonic channel signal from the monophonic signal is provided as the other stereophonic channel signal. A low-frequency signal attenuating resistor and a high-frequency signal attenuating filter are provided on the output side of the twin-T circuits to equalize peak values in frequency characteristics of the output signal of the twin-T circuits and thus obtained signal is amplified to be equalized in peak level to the monophonic signal and thereafter is applied to a subtractor together with the monophonic signal.

Abstract: A stereo demodulator capable of demodulating a composite signal without performing a switching operation is disclosed. A subcarrier generating circuit generates a square wave subcarrier signal V1 of 38 KHz which is in turn converted into a triangular wave subcarrier signal V4 of 38 KHz synchronized with the square wave subcarrier signal V1. The composite signal is converted into a current signal i which is then amplified by a voltage-controlled amplifier whose gain varies in accordance with the triangular wave subcarrier signal V4 applied thereto as a control voltage. Since the voltage-controlled amplifier is of such a type that the gain thereof logarithmically varies in accordance with the control voltage, the composite signal is amplified by a gain which varies substantially sinusoidally in accordance with the triangular wave subcarrier signal V4. As an output of the voltage-controlled amplifier is in the form of a pair of currents i.sub.R and i.sub.

Abstract: An amplifier circuit which amplifies an input signal with substantially zero distortion and can stably operate even at high frequencies is provided. A signal proportional to an input signal supplied to an input terminal is applied to an input terminal of a main amplifier. An output signal of this main amplifier is supplied through an impedance circuit to one of input terminals of a differential amplifier the other input terminal of which is supplied with the input signal to be amplified. An output signal of this differential amplifier is fed to a reference voltage input terminal of the main amplifier to determine a voltage potential of the input terminal of the main amplifier when a signal level of the input signal is zero, thereby distortion generated in the main amplifier being canceled.

Abstract: A power amplifier with a low distortion and a high power efficiency includes a first amplifier of the low distortion type for being powered by a first voltage source to amplify an input signal thereto to apply an output signal to a first terminal, and a second amplifier of the high power efficiency type for being powered by a second voltage source to amplify the input signal to apply an output signal to a second terminal. A load is connected between the first and second terminals. The output voltage of the second voltage source is greater than that of the first voltage source. A first feedback path is provided for feeding back the output signal of the first amplifier to an input thereof. A second feedback path is provided for feeding back the output signal of the second amplifier to the input of the first amplifier.

Abstract: A pulse-width modulation circuit of self-oscillation type produces a pulse-width modulated signal having a pulse width corresponding to an amplitude of an analog input signal. An integrator having an amplifier and at least one capacitor produces a triangle-wave signal. A comparator compares the triangle-wave signal with a reference voltage to generate a pulse signal. A delay circuit produces a delayed pulse signal in response to the pulse signal generated by the comparator. A feedback circuit feeds the delayed pulse signal back to an input terminal of the amplifier so that the self-oscillation is effected. The pulse-width modulated signal is derived from an output terminal of the delay circuit.

Abstract: A pulse-width modulation circuit detects a signal level or amplitude of an audio signal by means of an absolute value detecting circuit. The detected level is applied to a control terminal of a voltage-controlled oscillator. The output of the voltage-controlled oscillator is used as a carrier signal of the pulse-width modulation circuit, and the frequency thereof is controlled in such a manner that the carrier frequency is lowered as the audio signal level increases. Higher order harmonics of the pulse-width-modulated output signal both at high and low modulation factors are made substantially the same in amount. Thus, a band width required for the circuit is remarkedly narrowed, and improvement in distortion factor can be attained regardless of a low cost to manufacture.

Abstract: A small signal amplifying circuit suitable for use in a system such as a disc player-amplifier system in which metal contact portions such as connectors are used between a signal source and an amplifier. The small signal amplifying circuit according to the invention is an improvement of a circuit which is designed to eliminate distortion caused by the metal contact portions by transmitting a signal in a state in which the signal is superposed on a direct current. The circuit according to the invention includes a first transistor provided in a signal source and a second transistor provided in an amplifier which constitutes a differential amplifier with the first transistor. By negative feeding-back the output of the amplifier to the base of the second transistor, distortion factor, signal-to-noise ratio and stability in characteristics are remarkably improved.

Abstract: A pulse-width modulation circuit is provided which is simple in circuit construction and is free from the non-linearity of a waveform of a carrier signal. The pulse-width modulation circuit comprises an operational amplifier, a comparator and a feedback circuit. The amplifier has inverting and non-inverting input terminals and an output terminal with a capacitor connected between the inverting and output terminals. An input signal to be pulse-width modulated is applied to either one of the inverting and non-inverting input terminals depending upon whether the amplifier is used as inverting or non-inverting amplifier with respect to the input signal. The output from the amplifier is applied to one input terminal of the comparator, to the other input terminal of which a carrier signal, such as a sawtooth wave, a triangular wave, a sinusoidal wave, or other various periodic waves, is applied for the comparison with the input signal.

Abstract: A gain-controlled amplifier comprises input signal amplifying means; first and second bipolar transistor pairs each having a joined emitter connected to each other and driven by an output of the input signal amplifying means, bases of one transistors of said transistor pairs being commonly connected, and bases of the other transistors of said transistor pairs being commonly connected; and addition means for adding a signal representing a difference between collector currents of said the one transistor of the first transistor pair and said the other transistor of the second transistor pair to a signal representing a difference between collector currents of said the other transistor of the first transistor pair and said the one transistor of the second transistor pair, wherein a control voltage is applied between said two common-connected bases; an output of said addition means is negative-fed back to an input side of said input signal amplifying means; and either one of said signals to be added by said additio