| 摘要 |
PURPOSE:To eliminate a change in sound volume in normal operation and stereophonic widening operation by applying an (L+R) signal to one-side input terminals of an analog adder and analog subtracter and then by changing a signal applied to other-side input terminals over to an (L-R) signal. CONSTITUTION:Of a TV sound multiplex broadcast signal, the (L+R) signal and (L-R) signal are applied to analog adder 21 and analog subtracter 22. With switch means SW OFF, stereophonic widening opetation is performed and while a (2+ n)L-n.R signal is obtained from the output of adder 21, a (2+n)R-n.L is obtained from the output of subtracter 22. Normal stereophonic sound reproduction is carried out with switch means SW ON and while a 2L signal is obtained from the output of adder 21, a 2R signal is obtained from the output of subtracter 22. Therefore, the whole volume in stereophonic widening mode is (2+n)L-n.R+(2+ n)R-n.L=2(L+R), which is equal to the whole volume 2(L+R) in normal operation, so that a volume change can be eliminated on the whole. |
