Abstract: The invention relates generally to transmitting and receiving multiple channels of information, particularly audio information which represents a multidimensional sound field. More particularly, the invention relates to devices and methods which provide signals that are compatible with multi-channel receivers and with matrix decoders such as the decode MP-Matrix used for many motion picture soundtracks. In a multi-channel transmitter, a network prepares intermediate signals which are encoded by signal analysis processors into a signal for subsequent transmission or storage. In a multi-channel receiver, information extracted from the received encoded signal is combined in a network and processed by signal synthesis processors to provide output signals which are compatible with a matrix decoder.

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: A circuit providing a known change in a parameter of a function without interfering with the basic operation of the function is utilized in an audio circuit "loudness contour" control. Bass and treble controls function independently of the volume setting while desired contours are obtained at each volume control setting.