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STEREO_PREAMP

2017-01-04 17:47  
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STEREO_PREAMP
The output of the audio source is fed to the left and right inputs of the circuit (J1 and J2). Potentiometers R1 and R2 control the volumes of the input signals, while potentiometer R17 is a balance control. The incoming signals are coupled through capacitors C1 and C2 to the noninverting inputs of op amps IC1-a and IC1-b. Because IC1 operates as a single-supply amplifier, its output signal fluctuates above and below half of the supply voltage. The output signals of the op amps are coupled to the bases of two 2N2222 transistors (Q1 and Q2), which further amplify the left and right signals. Then, the outputs of the transistors are coupled to the bases of two more 2N2222 transistors (Q3 and Q4), further boosting the left and right signals. The transistor pairs also act as buffers.