1. Signal level matching: When connecting audio equipment, it is important to pay attention to the differences in input and output signal levels between each equipment. If the level of the input signal of the previous level equipment is too high, it will generate nonlinear distortion. Conversely, it will lower the signal-to-noise ratio of the playback system and even fail to drive the amplifier of the next level equipment. Therefore, when matching, it is important to note that the level difference between equipment should not be too large. If signal level mismatch occurs in practical use, it is necessary to reduce the input signal level through a attenuation circuit or increase the input signal level through an amplification circuit. For general dynamic microphones, the output voltage is a few millivolts, so a primary amplification circuit is required to amplify the signal and send it to the preamplifier circuit. For recording consoles, CD players, and LD players, the output signal level can reach 0.755-1V or above, so it can be directly fed into the preamplifier.

2. Impedance matching: In HI-FI audio equipment, for example, the output impedance of transistor power amplifiers is low, while the output impedance of electronic tube power amplifiers and other equipment is high. If they do not match the impedance when connected to the speaker, it will cause uneven distribution of output power of the amplifier, or the transient characteristics of the speaker will deteriorate due to excessive damping. There are generally two types of impedance matching connections: balanced and unbalanced. The so-called balanced type refers to the equal impedance of the two shielded wires transmitting signals to the ground. The so-called unbalanced type refers to a two core shielded wire, one of which is grounded. When the balanced output is connected to the unbalanced input, it must be matched by adding a matching transformer