A method and circuit for supplying power from a constantly available power source (20) to an audio power amplifier (14) for a speaker (12) utilizing input leads (16,18) having an audio signal. A pre-amplifier (24) is used for amplifying the audio signal having a difference in potential between the input leads (16,18). A switch (58) powers the audio power amplifier (14) and pre-amplifier (24) from the power source (20) in response to a control signal. The method and circuit is characterized by se...

An audio amplifier whose operating point and supply voltage can be change in response to a level of an input signal. The audio amplifier includes a delay circuit for delaying an input signal, an amplifier circuit having an amplification device for amplifying an output signal of the delay circuit, the amplifier circuit having a variable operating point, a power supply circuit capable of changing a supply voltage to the amplifier circuit, and a control circuit for detecting a level of the input si...

An audio full range speaker which achieves the propogation of a peaked wavefront from the diaphragm instead of generating a substantially planar wavefront as in the case of the common speaker construction utilizing a diaphragm driven as a piston. The speaker has a substantially planar, thin, flexible film forming the diaphragm mounted within a frame. The diaphragm is driven by a driver which imparts motion to the diaphragm at a small source area, the motion being imparted in a direction normal t...

A cable for use in carrying electrical signals in the audio frequency range. The cable includes an elongate metallic core which can be positioned at the center of the cable. In the case of the coaxial cable, a sleeve of a dielectric material is positioned about the core and a metallic shield is located outwardly of the sleeve and coaxially with the core. The cable also includes a layer formed of ferrite positioned between the sleeve and the shield which substantially increases the inductance of ...

An audio amplifier comprises a first current mirror having an input coupled to an output of a cascade differential pair and an output coupled to an output of a first constant current source. A second constant current source (Q16, Q18, CC10) supplies the voltage reference (Q15) of the first constant current source. Hitherto a resistor has been used instead of the second constant current source to reduce noise. However, using a resistor results in the amplifier having a relatively low power supply...

Audio equipment designed for use at widely varying ambient noise levels allows an audio signal to be amplified to enhanced levels under noisy conditions without added distortion near the high-amplitude end of its dynamic range. Detected or anticipated ambient noise conditions trigger a dynamic range controller to boost the gain of the audio signal to an extent inversely related to the audio signal amplitude. Thus, low-volume audio will be boosted to a great extent while the high-volume end of th...

An audio reverberator system having a piezoelectric transducer filter circuit for outputting selected audio vibrational frequencies having selected amplitudes responsive to inputs from an amplifier. The audio reverberator system includes a piezoelectric transducer having an intrinsic capacitance coupled to an additional circuit element to form a low-pass type filter circuit for attenuating higher frequency inputs to the transducer to provide a desired flat frequency response for an audio vibrati...

An audio encoder, generating a stereo signal based on a multi-channel signal, includes a downmix unit for downmixing a multi-channel signal exceeding two channels to a two-channel stereo signal, a first coding unit for generating a first coded signal by coding the downmixed stereo signal, a second coding unit for generating a second coded signal by coding information to restore the downmixed stereo signal to a multi-channel signal, a code size calculating unit for calculating a code size of the ...

An arrangement for adjusting the volume of a played-back signal by a microprocessor from an audio system, in which the volume is increased incrementally by a pulse generator. The instantaneous level of volume is tested constantly to determine whether it is equal to or higher than an previously-stored threshold. Further increase in volume is inhibited after the threshold has been attained, so that the current volume level is retained independent of actuation of volume controls. By actuating a swi...

A pre-amplifier for musical instrument audio signals which utilizes a solid state programmable logic device to control a plurality of solid state switches for routing the audio signals in preselected manner through successive stages of vacuum tube amplification.