Signal processor for sound image enhancement

Abstract

A signal processor for sound image enhancement of stereophonic signals provides fluctuating coherence between the left channel and right channel outputs by crossfeeding a high pass portion of the left channel to the right output and a like portion of the right channel to the left output. Preferably, the crossfeed path includes a high pass filter to eliminate crossfeeding of lower frequency range components which are often reproduced monaurally in prerecorded materials. The filtering is compensated for by a shelving filter introduced in the respective channel input to boost the power of the lower frequency components to be added with the crossfed signal to produce the channel output. In the preferred embodiment, an automatic gain control varies the gain of the crossfeed in accordance with the stereo content in the input channels. In addition, the gain control includes a control for user variation of the amount of coherence to be generated at the output. Furthermore, the present invention also provides a stereo detector circuit.