| 摘要 |
PURPOSE:To attain the ON/OFF control of the operation of a stereo sound field expansion circuit without increasing the number of terminals by taking notice of ON/OFF operation of the stereo sound field expansion circuit in response to a stereo/monaural discrimination output signal so as to switch forcibly an input signal to a stereo/monaural discrimination circuit externally thereby controlling the output signal. CONSTITUTION:Input signals L, R from input terminals 11L, 11R in a sound field expansion IC 10 are fed to a matrix circuit 14, in which difference and sum of signals are taken and the result is extracted externally via terminals 15, 16 and fed to a stereo/monaural discrimination circuit 20 via terminals 17, 18 through the connection at the outside of the IC. The discrimination circuit 20 discriminates whether the input signal is a stereo signal or a monaural signal in response to the difference signal and the sum signal to apply on/off control to the operation of the stereo sound field expansion circuit 12. Then a changeover switch 31 is inserted between an output signal 15 and an input terminal 17 for the difference signal and the changeover switch 31 forcibly switches the stereo/monaural discrimination output signal thereby applying on/off control to the operation of the stereo sound field expansion circuit 12 substantially. |
