| 摘要 |
PURPOSE:To prevent the abnormal operation owing to a positive feedback by connecting diodes between the output terminals of playback amplifiers and sound recording amplifiers having complementary output stages for each of right and left channels and grounding the other terminal of the diodes with a switch interlocked to a sound recording-playback changeover switch. CONSTITUTION:A switch 1 interlocked to a sound recording-playback changeover switch is on the playback side P (sound recording side R) and the emitter mid- point of a transistor constituting the complementary output stage of sound recording amplifiers 17, 18 for right and left channels is connected to the ground via diodes 25, 26 in the stage of playback. The mid-point of the complementary output stage is thus biased to the forward voltage of the diodes 25, 26, resulting in the decreased amplification factor of sound recording amplifiers 17, 18. Diodes 23, 24 are kept connected between the outputs of playback amplifiers 15, 16 of the right and left channels in this stage, but the outputs of the amplifiers 15, 16 are lower than the forward voltage of the diodes 23, 24 are therefore said amplifiers make normal amplification operation to amplify the playback signals from right and left playback input terminals (a), (b) and to output the same to playback output terminals (e), (f). |
