An audio interface is a device that connects audio equipment and acts as a bridge between analog and digital signals. Audio interfaces are typically used with front microphones, line-in, and a range of other input devices. According to the type of transmission signal, it can be divided into analog audio interface and digital audio interface.
Analog Audio Interface
The analog audio interface is a technology that uses changes in voltage or current to represent the strength and waveform of sound signals. It is a simple, intuitive, low-cost, and highly compatible audio transmission method that can transmit stereo or mono signals. Common analog input and output interfaces include: TRS interface (big/small three-core), RCA lotus plug, XLR XLR port, etc.
TRS interface
The meaning of TRS is Tip (signal), Ring (signal), and Sleeve (ground), which respectively represent the three contacts of this joint. What we see are three sections of metal columns separated by two sections of insulating material. The TRS interface can be used to transmit balanced or unbalanced signals, but we can't tell what kind of signal it transmits just from the interface.
There are three sizes of TRS interface: 1/4" (6.3mm), 1/8" (3.5mm), 3/32" (2.5mm). For most people, the 3.5mm TRS interface should be the most commonly used, which is the interface size of most earphones. The 6.3mm connector is more common on many professional equipment and high-end headphones, but now many high-end headphones are gradually switching to 3.5mm connectors. The 2.5mm TRS connector used to be more popular on mobile phone headsets, but it is rare now. The headphone jack is basically "dominated" by the 3.5mm jack.
Advantages of the TRS interface
01.Simple and intuitive, in line with human hearing habits, with a certain degree of reduction and realism.
02.The cost is low, the equipment is popular, the compatibility is good, and it is suitable for various occasions.
03.Balanced or unbalanced signals can be transmitted, improving anti-interference ability and dynamic range.
Disadvantages of TRS interface
01.In the process of recording, transmission, processing and amplification, it is easy to generate distortion and noise, which affects the signal-to-noise ratio.
02.It is not easy to perform complex editing and processing, such as editing, mixing, filtering, etc.
03.It is not easy for long-term preservation and reproduction, and it is easily degraded by environmental factors.
The TRS interface is suitable for scenes that require simple and intuitive, low cost, and high compatibility, such as recording studios, radio stations, record players, etc.
RCA lotus head
RCA lotus head is a technology that uses RCA terminals to transmit analog audio signals. It is named after the English abbreviation of Radio Corporation of America. The RCA lotus head adopts the method of coaxial signal transmission, the central axis is used to transmit signals, and the contact layer around the outer circle is used for grounding. Each RCA cable is responsible for transmitting the audio signal of one channel. Therefore, you can use RCA cables matching the number according to the actual needs of the channel. For example, to set up two-channel stereo, you need two RCA cables.
Advantages of RCA lotus head
01.What is transmitted is an analog audio signal, which does not need to be decoded, and can be directly connected to the post-stage amplification process.
02.It is the most common and basic audio connection method at present, and it is suitable for many occasions.
03.The cost is low, the equipment is popular, the compatibility is good, and the interface is flexible.
Disadvantages of RCA lotus heads
01.Analog audio signals are limited in bandwidth and are lost during transmission, so they are not suitable for long-distance transmission.
02.Only stereo or mono signals can be transmitted, and multi-channel surround signals cannot be transmitted.
03.It may be affected by external electromagnetic interference or ground loop interference, which will affect the signal quality.
RCA lotus head is suitable for scenes that require simple and intuitive, low cost and high compatibility, such as recording studios, radio stations, record players, etc.
XLR Canon port
XLR Canon Port is a technology that uses XLR terminals to transmit analog audio signals. It is a professional balanced audio interface that can effectively suppress noise and interference. The XLR Canon port usually has three contacts, which are positive phase (hot), negative phase (cold) and ground (ground). The XLR plugs we usually see are 3-pin, of course, there are also 2-pin, 4-pin, 5-pin, and 6-pin plugs. For example, in some high-end headphone cables, we will also see four-core XLR balanced connectors.
Advantages of XLR XLR
01.Balanced signals can be transmitted, improving anti-interference ability and dynamic range.
02.With locking design, it can prevent the plug from loosening or falling off.
03.There are high-quality metal shells and contacts, which can ensure signal quality and durability.
Disadvantages of XLR XLR
01.The cost is higher, the equipment is less, the compatibility is poor, and it is not suitable for ordinary consumers.
02.Larger size and heavier weight, not suitable for portable devices.
03.It needs to be used with devices that support balanced audio input and output, not for devices with unbalanced audio interfaces.
XLR canon port is suitable for scenes that require high fidelity and high definition, easy editing and processing, and long-term storage, such as movie theaters, digital music, and webcasting.
Digital audio interface
Digital audio interface is a technology that uses digital means to record, store, edit, compress or play sound. It is a high-fidelity and high-definition audio processing method. In terms of digital audio interfaces, we actually talk more about transmission protocols or standards. From the physical appearance of the interface, it is difficult to tell what type of interface it is. Common digital audio interfaces include: AES/EBU interface, S/PDIF interface, coaxial interface, optical fiber interface, etc.
AES/EBU interface
AES/EBU is a more popular professional digital audio standard. AES/EBU provides two channels of audio data (up to 24-bit quantization), the channels are automatically timed and self-synchronized. It also provides the method of transmission control and the representation of status information (channel status bit) and some bit error detection capabilities. Its clock information is controlled by the transmitter and comes from the AES/EBU bit stream. Its three standard sampling rates are 32kHz, 44.1kHz, and 48kHz, although many interfaces can work at other sampling rates.
There are many physical interfaces of AES/EBU, the most common is the three-core XLR interface, which is used for balanced or differential connections; in addition, there are audio coaxial interfaces using RCA plugs, which are used for single-ended unbalanced connections; and Use fiber optic connectors for optical connections.
Advantages of AES/EBU interface
01.It can transmit high-quality digital audio signals, improving the signal-to-noise ratio and dynamic range.
02.It can transmit multi-channel surround sound signals, which improves the sense of stereoscopic and immersion.
03.There are standard sampling rates and quantization bits to ensure signal consistency and compatibility.
Disadvantages of AES/EBU interface
01.The cost is higher, the equipment is less, and it is not suitable for ordinary consumers.
02.It needs to be used with devices that support digital audio input and output, not for devices with only analog audio interfaces.
03.It may be affected by external electromagnetic interference or ground loop interference, which will affect the signal quality.
The AES/EBU interface is suitable for scenes that require high-fidelity, high-definition, and multi-channel surround sound, such as movie theaters, digital music, and webcasting.
S/PDIF interface
S/PDIF is the abbreviation of Sony/Philips Digital Interconnect Format, which is a civilian digital audio interface protocol jointly developed by Sony and Philips. Due to its widespread adoption, it has become the de facto civilian digital audio format standard. There are generally three types of S/PDIF interfaces: RCA coaxial interface, BNC coaxial interface and TOSLINK optical fiber interface.
The S/PDIF interface can transmit LPCM streams and surround sound compressed audio signals such as Dolby Digital and DTS. In the international standard, S/PDIF needs BNC interface 75 ohm cable for transmission. However, due to various reasons, many manufacturers frequently use RCA interface or even use 3.5mm small stereo interface for S/PDIF transmission. Became a "civil standard".
Advantages of S/PDIF interface
01.It can transmit high-quality digital audio signals, improving the signal-to-noise ratio and dynamic range.
02.It can transmit multi-channel surround sound signals, which improves the sense of stereoscopic and immersion.
03.It has better compatibility and flexibility, and can use different types of physical interfaces.
Disadvantages of S/PDIF interface
01.The cost is higher, the equipment is less, and it is not suitable for ordinary consumers.
02.It needs to be used with devices that support digital audio input and output, not for devices with only analog audio interfaces.
03.It may be affected by external electromagnetic interference or ground loop interference, which will affect the signal quality.
The S/PDIF interface is suitable for scenes that require high-fidelity, high-definition, and multi-channel surround sound, such as cinemas, digital music, and webcasting.
Coaxial interface
The coaxial interface is a technology that uses coaxial cables to transmit digital audio signals. It is a high-fidelity and high-definition audio transmission method that can transmit LPCM streams and surround sound compressed audio signals such as Dolby Digital and DTS. There are two types of coaxial interfaces: RCA coaxial interface and BNC coaxial interface. The appearance of the former is no different from the analog RCA interface, while the latter is somewhat similar to the signal interface we commonly see on TVs, and has a locking design.
The coaxial cable connector has two concentric conductors, the conductor and the shield share the same axis, and the impedance of the line is 75 ohms. The coaxial transmission impedance is constant and the transmission bandwidth is high, so the quality of audio can be guaranteed. However, although the appearance of the RCA coaxial interface is the same as that of the RCA analog interface, it is best not to mix the cables. Since the RCA coaxial cable has a fixed impedance of 75 ohms, the mixed cables will cause unstable sound transmission and degrade the sound quality.
Advantages of coaxial interface
01.It can transmit high-quality digital audio signals, improving the signal-to-noise ratio and dynamic range.
02.It can transmit multi-channel surround sound signals, which improves the sense of stereoscopic and immersion.
03.It has better compatibility and flexibility, and can use different types of physical interfaces.
Disadvantages of coaxial interface
01.The loss of long-distance transmission is large, so high-quality cables and connectors are required.
02.It needs to be used with devices that support digital audio input and output, not for devices with only analog audio interfaces.
03.It may be affected by external electromagnetic interference or ground loop interference, which will affect the signal quality.
The coaxial interface is suitable for scenes that require high-fidelity, high-definition, and multi-channel surround sound, such as cinemas, digital music, and webcasting.
Fiber optic interface
Optical fiber interface is a technology that uses optical fiber to transmit digital audio signals. It transmits digital signals in the form of optical pulses, so it is the fastest transmission speed from a technical point of view. The English name of the optical fiber interface is TOSLINK, which comes from the technical standard formulated by Toshiba (TOSHIBA). Its physical interface is divided into two types, one is a standard square head, and the other is a round head that looks similar to a 3.5mm TRS connector that is common on portable devices.
The optical fiber connection can realize electrical isolation and prevent digital noise from being transmitted through the ground wire, which is beneficial to improve the signal-to-noise ratio of the DAC. However, because it requires a light emitting port and a receiving port, and the photoelectric conversion of these two ports requires a photodiode, there cannot be close contact between the optical fiber and the photodiode, which will generate digital jitter-like distortion, and this distortion is a superposition of. Coupled with the distortion during the photoelectric conversion process, it is much worse than coaxial in terms of digital jitter. Therefore, now the optical fiber interface has gradually faded out of people's field of vision.
Advantages of fiber optic interface
01.It can transmit high-quality digital audio signals, improving the signal-to-noise ratio and dynamic range.
02.It can transmit multi-channel surround sound signals, which improves the sense of stereoscopic and immersion.
03.Galvanic isolation can be achieved to prevent digital noise from being transmitted through the ground wire.
04.Suitable for long-distance transmission, not affected by electromagnetic interference.
Disadvantages of fiber optic interface
01.The cost is higher, the equipment is less, and it is not suitable for ordinary consumers.
02.It needs to be used with devices that support digital audio input and output, not for devices with only analog audio interfaces.
03.It is easy to generate digital jitter-like distortion and affect signal quality.
04.The interface is fragile and easily damaged.
The optical fiber interface is suitable for scenes that require high-fidelity high-definition, multi-channel surround sound, and long-distance transmission, such as movie theaters, digital music, and webcasting.