The preamplifier is used to shape the music signal to match the power amplifier. The power amplifier can amplify the current of the music signal enough to drive the speaker. For operational amplifiers, this chip was originally developed for analog computers and high-precision instruments, and later used in audio with superior performance. Of course, operational amplifiers can operate and amplify varying voltage signals in various ways. For example, the change law of pointer instrument is often nonlinear and must start from zero. If these instruments are used together with operational amplifiers, the pointer instruments can be completely in the linear range, and can also display the values in the interval range, so as to improve the resolution of the instrument display.