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1.输入电路 录音时,各种信号源阻抗和电压幅度都不同。例如内接驻极体电容话筒,在额定声压下。平均输出电压约0.5毫伏。收音检波输出约100毫伏。录音机或音频放大器的线路输出信号可高达1伏。对录音前置放大而言,首先要解决的是电平平衡问题。为了考虑小信号的灵敏度,录音放大器的增益都是按话筒信号进行设计的,因此录音前置放大器也可称为话筒放大器。对高电平信号,一般是采用电阻分压器、减少放大器级数或放大器加深度负反馈来实现。电阻分压器的优点是可以自由选择衰减量,如图3-9(α)所示。用电阻分压器衰减的方法,由于增加了信号源阻抗,影响录音的信
1. Input circuit recording, a variety of signal source impedance and voltage amplitude are different. For example, the electret condenser microphones are connected at the rated sound pressure. The average output voltage is about 0.5 millivolts. Radio detection output of about 100 millivolts. Recorder or audio amplifier line output signal can be up to 1 volt. Preamp amplification for recording, the first problem to be solved is the issue of level balance. In order to consider the sensitivity of the small signal, the gain of the recording amplifier is designed according to the microphone signal, so the recording preamplifier can also be called the microphone amplifier. For high-level signals, the resistor divider is generally used to reduce the amplifier stages or amplify the negative feedback of the amplifier to achieve. The advantage of a resistor divider is the freedom to choose the amount of attenuation, as shown in Figure 3-9 (a). Decay method with a resistor divider, due to increased signal source impedance, affect the recording of the letter