Stereo amplifier circuit with Av=200 (gain) composed of LM1877

As shown in the figure, it is a stereo amplifier circuit with Av=200 (gain) composed of LM1877. Two input audio signals are coupled to the input terminals 6 and 9 of LM1877 by two 0.1μF capacitors respectively, and then output from the 2 and 13 pins after amplification, and sent to the load resistor RL respectively. The amplifier gain is determined by the ratio of the 100kΩ resistor in the feedback loop between the 2 and 7 pins and the 510Ω resistor at the inverting input terminal 7 pin, so the amplifier gain (Av) is about 200. The two 1MΩ connected to the 1 pin are used to set the DC bias operating point of the amplifier, and at the same time, they form an input high-pass filter with two 0.1μF coupling capacitors respectively. The 2.7Ω resistor and 0.1μF capacitor connected in parallel with the two load resistors RL are used to filter out high-frequency noise.