Abstract: A sustaining device is described for prolonging the vibration of the strings of a stringed musical instrument, such as an electric guitar having two or three electromagnetic pickups. The pickups are all low impedance transducers that can function either as pickups or driver transducers, depending on whether they are connected to the input of the instrument pickup amplifier or to the output of the sustainer amplifier, respectively. When a transducer is being used as a sustainer driver, it cannot be simultaneously used as a pickup. Different methods of selecting transducers to function as pickups or drivers are described. The transducers, having only hundreds of wire turns instead of the usual thousands of turns for common pickups, have a flat audio frequency response that can be modified to produce a multitude of common pickup sounds by manipulating the transducer resonance frequency, bandwidth, and amplifier gain.

Abstract: A sustaining device is described for prolonging the vibration of the strings of a stringed musical instrument, such as an electric guitar having two or three electromagnetic pickups. The pickups are all low impedance transducers that can function either as pickups or driver transducers, depending on whether they are connected to the input of the instrument pickup amplifier or to the output of the sustainer amplifier, respectively. When a transducer is being used as a sustainer driver, it cannot be simultaneously used as a pickup. Different methods of selecting transducers to function as pickups or drivers are described. The transducers, having only hundreds of wire turns instead of the usual thousands of turns for common pickups, have a flat audio frequency response that can be modified to produce a multitude of common pickup sounds by manipulating the transducer resonance frequency, bandwidth, and amplifier gain.

Abstract: In a stereophonic expansion circuit, the (L+R) sum signal is spectrally modified by increasing the bass and treble frequencies relative to the midrange so as to compensate for a midrange frequency boost in the (L?R) difference signal. The stereophonic expansion effect and manipulation of the signal parameters are produced by active matrixing amplifiers.

Abstract: A peak to peak detector circuit for use in an audio system comprises a first amplifier having an input terminal for receiving an L+R AC audio signal and an output terminal which is serially coupled to a resistor in series with a capacitor for generating a variable dc voltage having a time vs. amplitude relationship corresponding to the input L+R AC audio signal. A clamping diode having a cathode electrode coupled to a reference potential and having an anode electrode coupled to the capacitor operates to limit negative amplitude excursions associated with the variable dc voltage to a predetermined minimal value. A rectifying diode having a cathode electrode coupled to the anode electrode of the clamping diode, and an anode electrode coupled to a second capacitor to charge the second capacitor responsive to the amplitude of said variable dc voltage operates to produce a dc output signal proportional to the peak to peak amplitude of said L+R audio signal.

Abstract: A stereophonic processing system provided with spatial expansion of the stereophonic sound so that a pair of spaced-apart loudspeakers will acoustically appear to be spaced apart further then they actually are. The spatial expansion circuit includes tonal compensation.

Abstract: There is provided an acoustic sound reproducing apparatus for a first audio signal and having an input terminal for receiving a second audio signal, a selector switch and at least one loudspeaker. The at least one loudspeaker is driven by an output signal from one of the first or second audio signal through the selector switch. As a result, the acoustic sound reproducing apparatus, and the apparatus providing the second audio signal, can commonly use a single loudspeaker or set of loudspeakers. When the external audio signal is selected, the internal loudspeaker(s) becomes part of the external loudspeaker arrangement for a surround sound system. When more than one loudspeaker is used, the loudspeakers are connected to each other in series when they are connected to be driven by the external second audio input signal instead of each being driven by their respective amplifiers.

Abstract: There is provided an acoustic sound reproducing apparatus for a first audio signal and having an input terminal for receiving a second audio signal, a selector switch and at least one loudspeaker. The at least one loudspeaker is driven by an output signal from one of the first or second audio signal through the selector switch. As a result, the acoustic sound reproducing apparatus, and the apparatus providing the second audio signal, can commonly use a single loudspeaker or set of loudspeakers. When the external audio signal is selected, the internal loudspeaker(s) becomes part of the external loudspeaker arrangement for a surround sound system. When more than one loudspeaker is used, the loudspeakers are connected to each other in series when they are connected to be driven by the external second audio input signal instead of each being driven by their respective amplifiers.

Abstract: An audio system has multiple amplifiers, each with power supply inputs and audio inputs and outputs, for driving audio speakers according to a selected one of at least two modes of operation in which a selection of the audio speakers and/or a required power output of the audio speakers differ between the modes. The invention is operable, for example, to an entertainment system that has internal and external speakers and associated amplifiers for switching between stereo and surround sound modes. At least two distinct power supply voltage sources are provided for the amplifiers, and a switching element operates upon switching between the modes to couple one or another of the distinct power supply voltage sources to the power supply inputs of respective ones of the at least two amplifiers. This the total audio output of the system from increasing, for example, when switching from two stereo outputs to five surround sound outputs.

Abstract: A sustainer for a musical instrument has at least one vibratory element arranged in a longitudinal direction. The sustainer provides a drive signal to a sustainer driver. The driver has a plurality of flux emitters disposed in an end-to-end relation perpendicular to the vibratory element. The driver emits a magnetic field to apply drive forces to the vibratory element in response to the drive signal. At least two of the flux emitters are magnetized by oppositely polarized permanent magnets. The flux emitters are arranged to narrow a magnetic gap between at least two of the flux emitters having oppositely polarized permanent magnets. The flux emitters are arranged such that they overlap each other in a direction perpendicular to the longitudinal direction in order to improve magnetic drive of the vibratory element when the vibratory element is located near the magnetic gap.

Abstract: A “floating” or “unipolar” DC supply is coupled to a filter comprising a pair of capacitors coupled in series across the supply output. Output voltages developed across the capacitors are applied to the supply inputs of an amplifier having an output coupled via a load to a common connection of the two capacitors. A bias supply, coupled in parallel with the filter, produces an output voltage representative of the relative values of the capacitor voltages which is fed back to an input of the amplifier via a threshold device. Under transient input signal conditions, which would tend to unbalance the filter capacitor voltages, the bias supply renders the threshold device conductive for diverting the transient from the amplifier input thus reducing the supply voltage imbalance and improving the transient recovery time of the amplifier.

Abstract: A sustainer is provided for prolonging the vibrations of strings of a stringed musical instrument. The instrument has at least one magnetic pickup means responsive to the vibrations of the strings. The pickup produces an output signal in response to the vibrations of the instrument strings. At least one control potentiometer provides the capability to control at least one parameter of the output signal. The sustainer comprises a string driver transducer capable of inducing vibrations in the strings, a sustainer amplifier having an input which accepts the pickup output signal, and an amplifier circuit which amplifies the pickup output signal to form a drive signal. The sustainer amplifier also has an output, from which the drive signal transfers sufficient energy to the string driver transducer to sustain the vibrations of the strings. A power supply provides electrical energy to the sustainer amplifier.

Abstract: A stereophonic audio processing system having left and right stereophonic sound channels with respective loudspeakers therefor is presented. The system is provided with spatial expansion of the stereophonic sound so that a first pair of spaced-apart loudspeakers will acoustically appear to be spaced further apart then they actually are. The audio system is provided with provisions for connecting a second pair of loudspeakers which can be spatially located at a distance between the loudspeakers which is larger than the first pair of loudspeakers. The audio system is provided with apparatus for providing stereo sound without spatial expansion when such secondary loudspeakers are used.