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在高传真音响放大器中,最近又发展了两种新颖电路,以增加放音效果,使音响更能逼真悦耳,其一是现场音感控制电路,另一是音源面立体效果控制电路。为了使扬声器放出的乐曲听上去犹似乐队呈现眼前、身历其境,必须特别对2～3千赫的中音频加以提升。图1就是这种现场音感控制电路,利用频率负反馈网络使2千赫的中音频得到提升。当电位器W转至上端时,由于电路中R_1～R_33和C_1～C_9所组成的桥T网络对2千赫的中音频吸收,使反馈至晶体管基极信号中的2千赫成分大大减少,于是放大器对2千赫的信号增益加大。当电位器W转至下端时,反馈电压经R_4反馈至基极,所以频响曲线比较平坦。图2是现场音感控制电路的频响曲线,图中曲线1为电位器W转至上端时的曲线,曲线2为转至中点位置时的曲线,曲线3为转至下端位置时的情形。
In the high-fidelity audio amplifier, two new circuits have recently been developed to increase the playback effect and make the sound more vivid and pleasant. One is the live audio control circuit and the other is the stereo effect control circuit of the audio source. In order for the speaker to release the music sounds like the band appeared in front, experienced, must be especially for 2 to 3 kHz in the audio to be enhanced. Figure 1 is the scene of the audio control circuit, the use of frequency negative feedback network to 2 kHz in the middle of audio is enhanced. When the potentiometer W goes to the upper end, the 2 kHz component fed back to the base signal of the transistor is greatly reduced due to the mid-tone absorption of 2 kHz by the bridge T network consisting of R_1-R_33 and C_1-C_9 in the circuit, The amplifier then amplifies the signal gain of 2 kHz. When the potentiometer W goes to the lower end, the feedback voltage is fed back to the base via R_4, so the frequency response curve is relatively flat. Figure 2 is the frequency response curve of the audio control circuit in the field. In the figure, curve 1 is the curve of potentiometer W going to the upper end, curve 2 is the curve of going to the midpoint, and curve 3 is going to the lower end.