Professional audio knowledge

- May 16, 2020-


Audio interface RCA analog audio

RCA connector is often called lotus head. Using RCA cable to transmit analog signal is the most common audio connection mode at present. Each RCA cable is responsible for transmitting the audio signal of one channel, so a pair of cables is needed for stereo signal. For multi-channel system, it is necessary to match the same number of cables according to the actual number of channels. For stereo RCA Audio Interface, the right channel is generally marked in red, and the left channel is marked in blue or white.


Audio interface - S / PDIF

S / PDIF (Sony / Philips Digital Interface) is a digital audio output interface jointly developed by Sony and Philips. This interface is widely used in CD player, sound card and household appliances. It can improve the sound quality of CD and give us more pure hearing effect. The interface transmits digital signal, so it will not be interfered like analog signal and reduce the audio quality. It should be noted that s / PDIF interface is a standard, and coaxial digital interface and optical fiber interface belong to the category of S / PDIF interface


Audio interface digital coaxial

Digital coaxial is an interface that uses S / PDIF interface to output digital audio. Coaxial cable has two concentric conductors, conductor and shielding layer share the same axis. Coaxial cable is a copper conductor isolated by insulating material, with impedance of 75 ohm. Outside the inner insulating material is another layer of circular conductor and its insulator. The whole cable is wrapped by PVC or Teflon sheath. The advantages of coaxial cable are stable impedance, high transmission bandwidth, and guaranteed the quality of audio. Although the standard connector of coaxial digital cable is BNC connector, RCA connector is widely used in the market.


Audio interface optical fiber

Optical fiber transmits digital signal in the form of optical pulse, and its material is mainly glass or plexiglass. The optical fiber also uses S / PDIF interface output, which has high bandwidth and small signal attenuation. It is often used to connect DVD player and AV power amplifier, and supports PCM digital audio signal, Dolby and DTS audio signal.


Audio interface XLR interface

Unlike RCA analog audio cable, the balanced analog audio interface uses two channels to transmit signals with the same signal and the opposite phase. The receiving device subtracts these two groups of signals, and the interference signals are cancelled out, so as to obtain high-quality analog signals. XLR interface and big three core interface are usually used in balanced analog audio. XLR, commonly known as XLR head, consists of three pin plug and locking device. Thanks to the locking device, the XLR connection is quite secure. The big three core interface adopts a plug with a diameter of 6.35mm, which has the advantages of wear resistance and is suitable for repeated plugging. Balanced analog audio connection mainly occurs in advanced analog audio equipment or professional audio equipment

This paper introduces the current mainstream audio interface: RCA analog audio, S / PDIF, digital coaxial, optical fiber, XLR interface use and connection. I hope it can help the readers in need.