Surround sound processor with improved control voltage generator

Abstract

A surround sound processor for presenting stereophonic audio signal on a number of loudspeakers surrounding a listening area, comprising an input matrix stage (6), a detector filter (8) and matrix circuit (10), a direction detector circuit incorporating improved filters, a novel detector splitter circuit (14) providing three direction signals from the two direction detector circuit outputs, a novel three-channel servologic circuit (16) with improved variable filters responding selectively to the rates of change of the direction signals and providing six control voltage signals (17) through linearity correction networks to six voltage-controlled amplifiers (18, 20, 22, 24, 26, 28), the outputs of which are combined in an output matrix (30) to provide a number of loudspeaker feed signals through buffer amplifiers (32, 34, 36, 38, 40) to the output terminals of the processor. The detector splitter circuit (14) is configurable to either a forward oriented or a backward oriented mode of operation, corresponding changes being made to the voltage-controlled amplifiers (18, 20, 22, 24, 26, 28) and output matrix circuitry (30). Additionally the detector splitter (14) may be switched to eliminate the third direction signal with corresponding changes to the output matrix circuitry (30).