Connection between audio equipment

The connection between the various levels of audio equipment is very important. If the connection is not done properly, it will not only affect the playback effect of the equipment, but may even damage the equipment. The following is an insight into the connection between the various levels of audio equipment.

a. Basic requirements for equipment connection

(1) Signal level matching: When connecting audio equipment, you must pay attention to the difference in input and output signal levels between the equipment. If the level of the input signal of the pre-stage equipment is too large, nonlinear distortion will occur. Otherwise, the signal-to-noise ratio of the playback system will be reduced, and even the amplifier of the next stage equipment will not be driven. Therefore, when matching, you must pay attention to the level difference between the equipment. If the signal level is not matched in actual use, the input signal level must be reduced through the attenuation circuit, or the input signal level must be increased through the amplification circuit. For general dynamic microphones, the output voltage is a few millivolts, so a first-stage amplifier circuit is required to amplify the signal and send it to the preamplifier circuit. For record players, CD players and LD players, since their output signal levels are above 0.755~1V, they can be directly sent to the preamplifier.

(2) Impedance matching: In Hi-Fi audio equipment, for example, the output impedance of transistor power amplifiers is low impedance, while the output impedance of tube power amplifiers is high impedance. If the impedances are not matched when they are connected to the speakers, the output power of the amplifier will be unevenly distributed, or the transient characteristics of the speakers will be deteriorated due to excessive damping. There are generally two types of impedance matching connections: balanced and unbalanced. The so-called balanced type means that the impedance of the two-core shielded wires transmitting the signal to the ground is equal. The so-called unbalanced type means that one of the two-core shielded wires is grounded. When the balanced output is connected to the unbalanced input, matching must be performed by adding a matching transformer.

b. Connection method of connector

In Hi-Fi audio equipment, the connection of equipment is completed through various connectors. The commonly used connectors are as follows.

(1) Two-core plug: Mainly used to transmit signals between various equipment and as an input plug for microphone input signals. It is divided into three types according to its diameter: 2.5mm, 3.5mm, and 6.5mm.

(2) Lotus* plug: Mainly used as input and output plug between audio equipment and video equipment.

(3) XLR plug: mainly used for connecting microphones and amplifiers.

(4) Five-pin socket (DIN): Mainly used for connecting cassette recorders and amplifiers. It can concentrate stereo input and output signals on one socket.

(5) RCA plug: RCA plug is mainly used for transmitting video signals in equipment.

(6) F and M plugs: They are mainly used for the input and output of radio frequency signals in audio-visual equipment.