RCA interface
First of all, RCA interfaces are very common in our daily life, such as speakers, TVs, power amplifiers and other equipment. The RCA interface is named after the Radio Corporation of America, which introduced the interface to the market in the 1940s and used it to connect devices such as phonographs and speakers. Therefore, the RCA interface is also known as the PHONO interface in Europe and the United States, which is also commonly known as the "Lotus interface".
In terms of signal transmission, the RCA interface adopts the method of coaxial transmission of signals, the central axis is used to transmit signals, and the contact layer around the outer edge is used for grounding. Each RCA cable is responsible for transmitting the audio signal of one channel, so users can use the RCA cables that match the number of channels according to the needs of the channels used. For example, if we want to form a two-channel stereo system, we need two RCA cables.
XLR interface
XLR connectors are also known as "cannons" because Cannon Electric, founded by James H. Cannon, was its original manufacturer. Their earliest product was the "cannon X" series, and later the improved product added a locking device (Latch), so an "L" was added after the "X". Later, a rubber compound (Rubber compound) was added around the metal contacts of the connector, so an "R" was added after the "L". Therefore, people later combined these three capital letters and named it the XLR interface.
The XLR plugs we usually see are 3-pin, of course, there are 2-pin, 4-pin, 5-pin, 6-pin. For example, in some high-end headphone cables, we often see four-pin XLR balanced connectors. The XLR interface is the same as the "big three-core" TRS interface, which can be used to transmit audio balanced signals.
Since the balanced signal is mentioned, let's briefly talk about the balanced signal and the unbalanced signal: after the sound wave is converted into an electrical signal, if it is transmitted directly, it is an unbalanced signal; if the original signal is inverted 180 degree , and then the original signal is transmitted at the same time. signal and an inverted signal, then this is a balanced signal. Balanced transmission is to use the principle of phase cancellation to minimize other interferences in the audio signal transmission process (to achieve clearer sound quality). Of course, the XLR interface mentioned above is also the same as the "big three-core" TRS interface, which can transmit unbalanced signals; therefore, if we look at the interface alone, it is basically impossible to see whether it transmits balanced signals or unbalanced signals.
