要重视改善前置放大器音质的设计.在设计前置放大器时,应考虑有较大的动态范围、较好的线性,失真要尽量小,信噪比要尽量高.本机的前置放大器包括射极跟随器、音调控制、平衡调节、音量控制和响度补偿等部分. 由于射极跟随器1BG_1的输入阻抗高,动态范围大,输出阻抗低,故可向后面的负反馈音调控制电路提供足够低的输出阻抗.在音调级中1BG_2、1BG_3组成差分式放大级,经放大后的信号由1BG_3的集电极同相输出,直接与1BG_4耦合.1R_(22)(33欧)为1BG_4提 Should pay attention to improve the design of the preamplifier sound quality.In the design of the preamplifier, should consider a larger dynamic range, better linearity, distortion should be as small as possible, the signal to noise ratio should be as high as possible.This unit’s preamplifier includes Emitter follower, pitch control, balance adjustment, volume control and loudness compensation etc. Since emitter follower 1BG_1 has a high input impedance, a large dynamic range and a low output impedance, it can provide enough negative feedback pitch control circuit Low output impedance. In the pitch class 1BG_2, 1BG_3 form a differential amplification stage, the amplified signal from the collector of the 1BG_3 output in phase, directly with the 1BG_4 coupling .1R_ (22) (33) for the 1BG_4 mention