Abstract: A configuration of audio system components, utilizing standard amplifier components, wherein the audio system remains balanced through the speaker input terminals. For each channel of the system, a preamplifier produces a balanced output signal. Two power amplifiers or similar devices are conventionally configured to accept positive and negative input signals. The negative signal output of the preamplifier is connected to the positive input terminal of one of the power amplifiers, and the positive output signal of the preamplifier is connected to the positive input terminal of the other power amplifier. The negative and ground input terminals of both power amplifiers are connected to system ground. The connections between the preamplifiers and the amplifiers may be effected by a unique cable designed for this purpose.

Abstract: In portable stereo radio receivers and television receivers, the loudspeakers therein may be separated only by a limited amount. This severely restricts the stereo image created by the loudspeakers. A circuit arrangement for creating an expanded stereo image may be incorporated in such receivers. This circuit arrangement includes, for each stereo channel, a first and a second all-pass 0.degree.-180.degree. phase shifter, wherein the first phase shifter shifts the input signal by 90.degree. at a frequency of 10 KHz, while the second phase shifter shifts the input signal by 90.degree. at a frequency of 100 Hz. The output from the first phase shifter in the left channel is combined with the output from the second phase shifter in the right channel to form the left channel output signal. Similarly, the output from the first phase shifter in the right channel is combined with the output from the second phase shifter in the left channel to form the right channel output signal.

Abstract: A method of creating an impression of sound from an imaginary source to a listener. The method includes the step of determining an acoustic matrix for an actual set of speakers at an actual location relative to the listener and the step of determining an acoustic matrix for transmission of an acoustic signal from an apparent speaker location different from the actual location to the listener. The method further includes the step of solving for a transfer function matrix to present the listener with an audio signal creating an audio image of sound emanating from the apparent speaker location.

Abstract: A high output power is obtained for an audio power amplifier using an amplifier circuit topology wherein channels or stages of a multi-channel class AB monolithic integrated circuit are paralleled in order to drive a low impedance dual voice coil speaker. The stages are paralleled by connecting their outputs through isolation resistors. These resistors prevent the differences in output bias voltages from resulting in a short circuit from power to ground. In addition, the resistors are sufficiently small to achieve the correct speaker damping factor, yet large enough to prevent excessive quiescent current. The separate amplifier channels or stages are paralleled through isolation resistors which increases current drive resulting in a higher output power to the loud speaker.

Abstract: A television receiver for automatically determining from a command issued from a controller, the control of power on/off, picture brightness and picture contrast of a video projector using a video projector controller contained in the television receiver and for controlling the deployment and retraction of a screen using a screen controller also contained in the television receiver.

Abstract: The present invention resides in an audio amplifier circuit which includes an output terminal of an IC connected to a power amplifier circuit, a resistor having one end connected to a negative feedback input of the power amplifier circuit and the other end connected to a certain terminal other than the output terminal of the IC, a first capacitor connected between the output terminal and a loud speaker and a second capacitor connected between a wiring connecting the output terminal to the loud speaker and the certain terminal. A reduction of low frequency gain determined by a time constant of the first capacitor and an impedance of the loud speaker is corrected by an increase of of low frequency amplification gain determined by a time constant of the second capacitor and the resistor.

Abstract: An audio circuit for use in a television receiver and the like compensates for the capacity shortage of a speaker box or low frequency characteristic of the speaker to reproduce vivid and voluminous low frequency sound. L and R signals of the audio signal are mixed, and then an arbitrary low frequency band component is extracted therefrom by a filter having an arbitrary frequency characteristic, and extracted component is bisected by a distribution means, and only low frequency band component is added to the original L and R signals to reproduce the audio signal which is voluminous in a low frequency band. With a low frequency band which is difficult to be reproduced by a speaker, the harmonic is stressed by full-wave rectification means to stress low frequency sound feeling, and when a switching circuit is provided, low frequency sound stressing by an amplifier and low frequency sound harmonic stressing by full-wave rectification means can be easily switched.

Abstract: A surround sound converter for home audio systems includes outputs for a left front speaker, a right front speaker, a left rear speaker, a right rear speaker, and an auxiliary output to accommodate a rear auxiliary amplifier. The surround sound converter also includes an input for the left and right channel speaker output of an amplifier, a receiver, or any stereo signal device which has an audio amplifier. At least one potentiometer controls the volume balance between the front and rear speakers. A left and right capacitor are used to drive the left and right rear speakers, respectively. An auxiliary output is provided to accommodate adding a rear auxiliary amplifier. A surround sound converter for vehicle audio systems utilizes an automotive stereo. A left front speaker and right front speaker are connected to the normal speaker outputs of the automotive stereo. The left rear speaker is connected to the left rear signal negative and the right rear signal negative.

Abstract: The present invention relates to sound reproduction apparatus comprising stereophonic amplifier means for amplifying left and right signals from any stereo emission source, and a plurality of loudspeakers disposed in two groups, namely one group on the left of a listening direction and another group on the right thereof, each group respectively receiving the amplified left signal and the amplified right signal. The number of said loudspeakers is even and not less than four, the loudspeakers being situated in pairs on axes that are vertical or substantially vertical, with all of the emission faces of said loudspeakers being placed on a surface of continuous curvature, and with the respective vertical and horizontal distances between said loudspeakers being determined as a function of the size of the loudspeakers and as a function of the listening volume.

Abstract: A bass audio circuit includes a first filter network which receives left and right channel input signals and produces two filtered signals by attenuating frequencies in the input signals above a first cutoff frequency. The two filtered signals are summed to create a first monophonic signal. A second filter network produces attenuated frequencies in either the input signals or in the first monophonic signal that are above a second cutoff frequency which is lower than the first cutoff frequency. The signals from the second filter network are combined and passed through a phase inverter to derive a second monophonic signal. An output stage individually amplifies the two monophonic signals which then either are applied to a dual voice coil woofer, or are electrically summed and applied to a single voice coil woofer. Alternatively, the two monophonic signals are first summed and applied to a single channel amplifier which drives a single voice coil woofer.

Abstract: An apparatus for multiplexing audio signals in a disc-shaped video-song medium which includes a plurality of digital audio channels having stereo accompaniment music recorded therein, and a plurality of analog channels having stereo accompaniment music which includes a singer's singing voice, and playback system thereof, are disclosed. When the video-song mode is established, the apparatus for multiplexing the audio signals adjusts the audio levels of both the stereo accompaniment music and the stereo accompaniment music that includes a singer's singing voice to adequate audio levels by means of an audio level adjustment responsive to a change in the resistances in the variable resistors included in an audio multiplexing section. The apparatus multiplexes the audio signals. Accordingly, the user can effectively practice a video-song in harmony with either the stereo accompaniment music or the stereo accompaniment music that includes a singer's singing voice.

Abstract: A surround-sound system for use with conventional TV sets, using a wireless remote bipolar rear speaker (or two conventional speakers fed out of phase) for the surround (difference) channels. The use of the rear speaker(s) and the mono (left plus right) front speaker on the TV set creates "phantom" left and right front speakers, and allows full surround sound without modification to the TV set or additional amplifiers or speakers.

Abstract: In a mono/stereo input circuit for use in an audio equipment, and more particularly in a circuit for automatically recognizing and receiving mono/stereo audio signals, although a mono connector is inserted into a stereo jack, such an insertion of the mono connector is automatically recognized and then a stereo circuit can operate as a form of a mono circuit. The circuit for automatically recognizing and receiving the mono/stereo audio signals utilizes a fact that one connection terminal of the jack is grounded or not according to a type of the connector such as a mono connector and a stereo connector which is inserted into the jack. Accordingly, a resistor used as a voltage generator generates a generation voltage according to such a connector recognition. Also, using a difference between the generated voltage, the analog switches are turned on or off, to obtain a mono or a stereo audio signal processing circuit according to a type of the inserted connector.

Abstract: The apparatus includes output stage amplifiers for receiving the respective outputs of preamplifiers provided in correspondence to the left and right channels in a stereo system. Negative feedback circuits are provided in the respective output stage amplifiers for reducing the amount of low-band negative feedback. Switch circuits are turned on in response to feedback signals from the respective negative feedback circuits for supplying the feedback signals at the input to the output stage amplifiers.

Abstract: A combination speaker and amplifier unit has speaker located on the front of a cabinet and speaker wire receptacles located in the back of the cabinet for providing speaker wire connections to a stereo unit. Also in the back of the cabinet is a power booster amplifier mounted thereon for amplifying the left and right stereo signals provided by the stereo unit. A power cable extends out the base of the power booster amplifier which is mounted to a cut-out section of the back of the cabinet so as to place the power booster amplifier within the cabinet, The power cable has a cigarette lighter adapter plug allowing the power booster amplifier to by powered by the power supplied to the cigarette lighter socket of an automobile.

Abstract: A single monolithic integrated circuit which may be used with an external audio integrated circuit to provide various analog support functions for the external audio integrated circuit, including, microphone amplifier circuitry, speaker/headphone drivers and power control.

Abstract: An operational amplifier is applied with an audio signal at a non-inverting terminal thereof for amplifying the audio signal. A crosstalk cancelling circuit is provided for reducing the output of the operational amplifier to a level of crosstalk generated at the non-inverting terminal. The output of the crosstalk cancelling circuit is applied to an inverting terminal of the operational amplifier so as to cancel the crosstalk.

Abstract: A circuit for coupling a 2- or 4-channel audio deck to 2- or 4-speakers in a car stereo audio system to increase the signal level output without raising the supply voltage or increasing the noise. The circuit comprises unity gain inverting and non-inverting amplifiers each connected in one of four channels, with the outputs combined to provide left and right channel outputs for series connection, respectively, to the left and right channel speakers.

Abstract: A circuit for directly differentiating stereo and mono signals regardless of whether a pilot carrier signal is present. The circuit generally includes a detection circuit coupled to a control circuit. The detection circuit subtracts the left and right audio signals, and the control circuit compares the resulting difference to a reference signal. When the reference signal exceeds the difference between the left and right signals, the control circuit judges that the inputs are mono. The circuit is advantageously used to automatically disable a repercussion function of a stereo system when a mono signal is received.

Abstract: In an apparatus for reproducing media having a channel 1 including only accompanied signals and a channel 2 including accompanied signals and song signals, a song signal separator which includes a gain adjusting means for inputting signals of a channel 1, a subtracting means for subtracting the output signals of the gain adjusting means from the signals of a channel 2, and a control means for inputting control starting signals, signals of the channel 2 and the outputs of the subtracting means so as to control the gains of the gain adjusting means. A song signal separator which is capable of drawing out songs only even when the recording level of the accompaniments of the channel 1 is different from the recording level of the accompaniments of the channel 2.

Abstract: A pair of amplifiers are coupled to respective loudspeakers. The output terminals of the amplifiers are coupled to each other through a filter network for reducing the effects of time delayed acoustic feedback from the ambient surroundings and from the other displaced loudspeaker on the amplifiers.

Abstract: A vocal sound can be erased by a simple arrangement. An audio reproducing apparatus in which a sum signal and a difference signal of left and right signals of a stereophonic signal are supplied thereto, a left signal and a right signal are obtained from the sum signal and the difference signal and the left signal and the right signal are respectively supplied to a left signal output terminal and a right signal output terminal includes switches (SW.sub.1 to SW.sub.4) for supplying the difference signal to the left and right signal output terminals (T.sub.L, T.sub.R) by switching the left and right signals.

Abstract: A two channel audio switcher includes two analog switches, which may be implemented as a CMOS integrated circuit, receiving at their control input ports a complementary pair of drive signals, typically square wave, so as to toggle their outputs at a supersonic rate, which may be made variable. The switcher may receive as input two channels of a stereophonic source, two independent audio sources or a common monophonic source. The outputs typically drive an audio output unit such as the transmitter of a radio broadcasting system, an audio recording system, or amplifiers, controls and loudspeakers of a sound reinforcement system in an auditorium or studio. The system may be monophonic or stereophonic. In a stereophonic a.m. broadcasting system such as the Kahn independent sideband system, alternate switching allows each sideband to be modulated to full available power, thus allowing an increase in the apparent radiated power.

Abstract: An amplifier for sound signals is made up of an even number of power amplifiers each of which have each an output, wherein each amplifier output can be switched to a first terminal of an associated loudspeaker and in which the second terminals of the loudspeakers can be switched to an output of a buffer amplifier. In order to minimize power losses, the buffer amplifier supplies at its output a DC voltage which is about half the value of the supply voltage of the power amplifiers. In addition, half the power amplifiers supply an output signal that is inverted relative to their input signal.

Abstract: A surround processor includes a time constant processing circuit for smoothing directional information signals from a detector with continuously variable time constants in order to generate one or more control voltage signals. The time constants produced by the circuit are continuously variable and responsive to both the rate of change and the amplitude of the directional information signals, such that as the difference between the controlled voltage signals and the directional information signals increases, the value of the time constants decreases to permit the control voltage signals to closely follow the directional information signals, and as the difference between the control voltage signals and the directional information signals decreases, the value of the time constants increases so that variations in the control voltage signals are smooth. Split-band processing of input audio signals to the processor is also accomplished without the necessity of placing filters directly in the audio path.

Abstract: A bass compensation circuit for use in a sound reproduction device is provided with a second-order positive feedback type high-pass filter. The filter has an operational amplifier and a first positive feedback resistor, a first variable resistor connected to an input terminal for receiving an input signal, coupled with a second variable resistor for volume control, and a second resistor for determining a Q-value and a cut-off frequency of a second-order positive feedback type high-pass filter. The first variable resistor and the second resistor are inserted in series between the first resistor and the ground. Thus, the bass compensation circuit can amplify only low frequency signals which do not serve as a masking sound used in masking middle and high frequency signals and has a low level when the sound volume is low. Moreover, the Q-value and the cut-off frequency of the second-order positive feedback type high-pass filter can continuously be changed by using the second variable resistor.

Abstract: A method and apparatus for generating control voltage signals in a surround sound processor is disclosed which utilizes a one-shot monostable multivibrator for minimizing intermodulation distortion while following rapid directional changes, yet minimizing intermodulation distortion. The apparatus includes a circuit for smoothing the directional information signals derived from audio input signals each with a continuously variable time constant to generate a corresponding control voltage signal, such that each time constant depends inversely upon the magnitude of the difference between the directional information signal applied thereto and the corresponding control voltage signal generated thereby.

Abstract: In a multi-channel audio circuit, a plurality of input signals are supplied to corresponding amplifiers each respectively connected to speakers, at least one of the input signals being inverted. The speaker connected to the amplifier receiving the inverted signal is connected at a polarity opposite that of the other speakers.

Abstract: A volume control circuit in a system including a tuner and a deck which are prepared as separate components and combined together. The tuner has a control purpose audio input terminal, an audio output terminal, and an audio output level variable circuit provided between the control purpose audio input terminal and the audio output terminal. The tuner further includes a controller for setting the gain of the audio output level variable circuit. The deck has an audio output terminal connected to the control purpose audio input terminal of the tuner so as to issue an audio signal from the audio output terminal of the tuner. The controller of the tuner controls the gain of the audio output level variable circuit to vary the output volume.

Abstract: An audio system for a vehicle wherein the feeling of a passenger on the rear seat of the vehicle in listening to sound can be improved only by operation of a sound volume switch of a manually operating section without the necessity of operation of any other switch. A microcomputer detects an attenuation amount from an operating section and outputs to an equalizer, when the attenuation amount is lower than a predetermined value, a medium and high frequency sound region controlling signal for attenuating sound in the medium and high frequency sound regions in a substantially inversely proportional relationship at least to the attenuation amount. A plurality of rear loudspeakers receive the medium and high frequency sound region controlling signal from the equalizer and output sound of an attenuation information signal wherein sound in the medium and high frequency sound regions is attenuated.

Abstract: An amplifying circuit of the invention comprises: a high frequency amplifying circuit for amplifying high frequency; a low frequency amplifying circuit for amplifying a low frequency; input filters which are provided on the input side of the respective amplifying circuits so as to pass the frequency components thereof; output filters having the same characteristics as those of the input filters; and an adding circuit for adding outputs of the output filters. Therefore, an output dynamic range of the whole amplifying circuit is equal to the sum of the dynamic ranges of the respective amplifying circuits, so that a large output which is not distorted even if a sound volume is raised is derived.

Abstract: An audio signal processing channel includes a bias network for deriving a bias voltage which is coupled to a point within the channel from the supply voltage. In order to inhibit audible transients or "pops" due to the rapid reduction of the bias voltage when the voltage supply is deenergized, a diode is coupled between the bias network and the voltage supply so as to selectively decouple a filter capacitor of the bias network from the voltage supply and associated loads when the voltage supply is deenergized. As a result, the bias voltage is gradually reduced at a controlled rate of change which is independent of the impedances of voltage supply and associated loads. Such a "pop" suppression arrangement is particularly desirable when it is not possible or practical to "mute" the output amplifier of the channel.

Abstract: A level control circuit for low and medium sound having an audio signal amplification output circuit, a low and medium sound signal detection circuit, and an amplification output circuit includes a control signal detection circuit for detecting a peak of the output signal and a gain control circuit for controlling a signal gain according to the output of the control signal detection circuit. The level control circuit may drive an exclusive speaker for low and medium sound with controlling the gain of the low and medium sound signal detected from left and right audio signals.

Abstract: An audio system for use with a mobile radio. More particularly, a microprocessor controlled audio system capable accepting multiple audio input signals and providing an amplified audio signal to a local speaker and a remote speaker without the use of transformers or relays, and capable of driving the speakers either individually or simultaneously. The system provides for increased versatility in output configurations, and allows for microprocessor-controlled muting and power output level switching.

Abstract: In a sound system having a sound source for generating sound signals, a low-impedance amplifier for amplifying the generated sound signals, and high-impedance loudspeakers for reproducing audible sound from the amplified sound signals, an impedance conversion device having a step-up transformer section is disconnectably connected between the amplifier and the high-impedance speakers. The output side of the low-impedance amplifier is also connected directly to low-impedance loudspeakers. Thus the sound system can be operated to selectively broadcast either monaural sound or binaural stereo music of high quality.

Abstract: An improvement in the high frequency sound quality of audio circuits using copper electrical interconnections is realized by replacing copper electrical interconnections with interconnections of a material exhibiting a greatly reduced skin depth at audio frequencies. At the moment, without the availability of practical room-temperature superconductors, the most practical method is to use a material possessing a high magnetic permeability. By this means, phase dispersion due to the skin effect is virtually eliminated.

Abstract: A reverberation circuit comprises an amplifier, attenuation circuit, a feedback component, and a delay circuit. The amplifier, delay circuit, and feedback component form a feedback loop. The amplifier amplifies an input signal supplied to an input terminal and outputs an amplified signal to the delay circuit. The output of the delay circuit is fed through a feedback component back to the amplifier. The feedback component controllably varies the feedback amount of the delayed signal to the amplifier in accordance with the desired depth of reverberation. An attenuation circuit is placed in the feedback loop, or before or after the feedback loop. The attenuation circuit selectively attenuates the level of specific frequency component of a signal passing therethrough whose frequency may be different depending on the depth of reverberation or feedback amount.

Abstract: A remote control circuit for remotely controlling a power source and a volume of a main set from a stereo-headphone composed of a remote control transmitting circuit arranged in a headphone, and a remote control receiving circuit arranged in a mainset.

Abstract: A television receiver includes a stereo amplifier having separate bass, treble and gain controls, for driving left and right channel loudspeakers. Separate bandpass circuits supply portions of the respective channel signals for phase inversion and feed back to respective summation circuits in the outputs of the corresponding opposite channel to produce an extended stereo effect. A switch simultaneously activates the syereo extender circuitry and operatively couples the bass and treble controls to the gain control for extending the frequency response characteristic and the volume level of the channels.

Abstract: An acoustic reproduction range expanding apparatus includes a closed or bass-reflex speaker system which has a low-frequency drive speaker and can reproduce a sound to a predetermined lowest frequeny. A port portion adapter consists of a mounting portion attached to an openng formed in a closed cabinet or a bass-reflex port of a bass-reflex cabinet, and a port portion. The port portion constitutes a Helmholtz's resonator together with the cabinet when the port portion is attached to the cabinet, and has a port shape so that a resonance frequency becomes lower than the lowest frequency. A drive portion adapter consists of an amplifier for driving the low-frequency drive speaker, and eliminates or invalidates an internal impedance inherent to the low-frequency drive speaker. The amplifier generates a negative impedance component in an output impedance.

Abstract: An automatic loudness control circuit for automatically controlling the magnitude of boosting of the low-frequency component of an audio signal in accordance with the output signal level of a power amplifier for driving a loud-speaker. The low-frequency component of the output signal from an audio signal source is boosted by a low frequency boosting circuit to prepare a low-frequency boost signal, which is then added to the output signal of the source, and the resulting signal is fed to the power amplifier. The magnitude of boosting by the boosting circuit is controlled according to the output level of the power amplifier and is therefore increased as the output level lowers. Consequently, the circuit assures optimum loudness control at all times, permitting the loudspeaker to produce dynamic sounds.

Abstract: An improvement in the high frequency sound quality of audio circuits using copper electrical interconnections is realized by replacing copper electrical interconnections with interconnections of a material exhibiting a greatly reduced skin depth at audio frequencies. At the moment, without the availability of practical room-temperature superconductors, the most practical method is to use a material possessing a high magnetic permeability. By this means, phase dispersion due to the skin effect is virtually eliminated.

Abstract: An output level control apparatus which operates according to a reproduced signal level from a digital recording apparatus. The output level control apparatus includes a signal level detection device which compares the level of the reproduced signal with a predetermined level to decide if a level of the reproduced signal should be changed. The output level control apparatus further includes a device which attenuates the level of the reproduced signal to a suitable level when the signal level detection device determines that the reproduced signal should be changed.

Abstract: An electronic switching system is presented for use by consumers. Inputs are connected to the circuit which detect which input is producing a signal. The circuit then allows that signal to pass through to be reproduced on output speakers. If both of two inputs are "on," producing two signals, the system toggles between the signals thus reproducing a toggling signal at the speakers. The system may also be adapted to accommodate three or more input signals which would then produce either one output if only one is "on" or a toggling output between those inputs that are "on.

Abstract: In an adjustable power fader device for a loudspeaker system with at least four speakers right and left channel input signals are received by respective power fader circuits. Each power fader circuit has a variable resistor connected across its input terminals and a series of at least two speakers across its output terminals. The sliding terminal of the variable resistor is connected via a capacitor to the mid point of the series of speakers, one of which has good low pitch sound reproduction. The two sliding terminals of the respective power fader circuits are movable together and the level of audio signals applied to the loudspeakers is accordingly adjusted.

Abstract: To enhance low and high frequency components in a sound signal, low frequency components are used to generate new yet lower frequencies (subharmonics), and high frequency components are used to generate new yet higher frequencies (harmonics), the new frequencies added to the original signal thereby increasing the original signal bandwidth.

Abstract: A two-channel audio amplifier for use in a vehicle sound system is provided. Each channel drives a pair of loudspeakers and includes a common amplifier connected to drive one terminal of each speaker. The remaining speaker terminals are connected to the outputs of a pair of additional amplifiers. Signals of one phase are applied to the common amplifier. Signals of opposite phase are applied to the additional amplifiers. Signals in phase with the common amplifier are applied to the inputs of the additional amplifiers through field-effect transistors. Control signals applied to the control electrodes of the transistors control the magnitude of the applied in-phase signal to independently control the output level of the speakers.

Abstract: An audio mixer for combining stereo phonograph, stereo high impedance and low impedance input signals having a means for audio previewing one or more of said inputs simultaneously including a means for visually indicating which signals are being previewed, further including a means for audio previewing said signals in a monophonic signal, further including a means for combining said inputs in the final amplifier stage such that the output signal is in a monophonic state, further including a means for disabling said low impedance input from the final output means.

Abstract: The disclosure relates to an audio signal reproduction system having one or more of the following features: (1) a loudspeaker having (a) a flat frequency response and (b) a predetermined power response; (2) two loudspeakers adapted to be positioned relative to one another so that they reproduce a stereophonic image substantially independent of the listener's position along a listening line spaced from the loudspeakers and nonintersecting a line extending between the two speakers; (3) an improved cross-over network having a substantially constant input impedance as a function of frequency; (4) a power sensor for sensing the power applied to a transducer so that audio signals are transmitted over a first signal path through the system when the sensed power is above a predetermined minimum level, and over a second path when the sensed power falls below the minimum level; (5) a power monitoring circuit to prevent a loudspeaker driver from being overdriven; and (6) a circuit for substantially balancing the signal

Abstract: A circuit for processing an angle modulated signal having amplitude modulation signal components in stereophonic broadcasting systems. An inverse modulation of a signal to be detected is provided over a first signal amplitude range, and a constant signal level is provided over a remaining range for signals having a marginal amplitude level. The discontinuity in the control range avoids noise expansion for high negative amplitude modulator levels for the signal to be angle modulated.