Today there are so many slots and connectors that it is sometimes difficult to deal with one of them. So, often there are problems with buying a new device and connecting some additional devices to it. Today we will learn all about S / PDIF - what it is, why, and why.
The concept
Interestingly, the international standard allows the use of both S / PDIF and S / P-DIF options. He has his own decryption, which allows us to understand who developed this standard. Sony / Philips Digital Interface Format stores a set of protocol parameters with hardware implementation. It has the ability to transmit digital sound from the first audio device to the second.
Considering S / PDIF, we will deal with its physical and systemic part. The physical parameter makes it possible to find out in what way the signal is transmitted and through which channels, and the system parameter - which protocol is used.
Specification
Before we figure out the scope of this interface, we’ll understand what it does. In general, this format allows several types of cables and connectors. So the world has access to digital S / PDIF, coaxial and optical. There are corresponding adapters and adapters for all these options. It is possible to use optical instead of coaxial and vice versa. The only thing that, in addition to adapters, you need an external power supply.
Ancestor
The development of this interface began with the then existing professional AES / EBU standard. The cipher first became known in 1986. Then the Society of Sound Engineers and the European Broadcasting Union worked on it . The revised version began to be used in 1992, after which it underwent changes in 2002 and 2009.
As usual, there is some difference in interfaces. It can be defined using established standards.
Difference
If you do not know anything about S / PDIF, what it is and what you need it for, then most likely you have never heard of AES / EBU. The last standard was invented for DAT and CD formats, which are encoded using pulse-code modulation. The interface uses BMC code. This means that the transmission of information occurs with any indicator of the sampling frequency, and the restoration of the frequency passes through the decryption of data.
The AES standard was introduced in three versions. Everyone worked with a resistance index of 110 Ohms, with a balanced connection, depending on the modifications, a shielded pair or category 5 cable was used. The standard of the connectors also differed, first XLR or D-25, later RJ-45. The signal level is 2-7 V.
Modulation remained unchanged and went through coding. The subcode data is represented by an ASCII ID text. The maximum distance at first was only 100 m, later - 400 m. The resolution reached 24 bits.
Before everyone knew about S / PDIF, what it was and what it was for, an intermediate version of AES3id appeared. He already worked with a resistance of 75 ohms, the connection was unbalanced, the cable was coaxial. The connector format again changed to BNC, and the signal level dropped to 1 V. The maximum distance reached 1000 m. The resolution remained unchanged - 24 bits.
This intermediate option in many respects dictated the specification of the novelty. So, the monitored standard also worked with a resistance of 75 ohms, had an unbalanced connection. The cable was both coaxial and optical, depending on the type. The connector again changed the format: RCA or TOSLINK. The signal level has become half as low as 0.5 V. The subcode data has changed, which is equipped with SCMS copy protection technology. The maximum length decreased and became only 10 m, and the ability to 20 bits optionally showed all the same 24 bits.
Types
As we said earlier, there are three types of this standard. There is optical S / PDIF, digital and coaxial. The first TOSLINK got its name thanks to the developer Toshiba. This is a fiber optic standard. It can often be found in household audio devices, computer sound cards, etc. MiniTOSLINK with a 3.5 jack form factor has recently become popular. They can be found in some laptop models, in which the S / PDIF output is combined with a headset.
The coaxial type has a resistance of 75 ohms, connected via an RCA interface. If ordinary audio cables, which are also called tulips, are not suitable for you, then look at the coaxial standard. To work correctly, it is terminated on both sides, and the input and output impedance are 75 Ohms.
S / PDIF Digital Audio - Third Type, Level-by-Level (TTL). The standard is based on a bipolar circuit for constructing transistors and resistors. Transistor-transistor logic is based on two steps, although not always. First> 2.4 V, second 0-0.4 V. Outputs of this type can be found on sound cards.
There is a simple explanation of the classification, so as not to get confused and normally deal with the fact that this is S / PDIF. This digital sound interface, as we have already discovered, can be digital or optical. If your home has a good audio system or sound center, it is better to connect it through this type of connector. The sound quality is much better than through the standard format.
The improvement is due to the fact that the sound, passing through the high-frequency filling and collecting all the "dirty" pulses, is output not through the analog format, but digital, which prevents the sound from distorting. If you use the optical standard, you can forget about the interference on a common drive.
Application
The reviewed standard was first used in CD players. After they discovered that it can be used as a connector and a sound transmitter in other audio devices. So, this interface began to appear in MiniDisc players and on sound cards for PCs. Some observant drivers might have noticed the standard in car sound. This was especially a find for those who are tired of the mess of a large number of cables. Now the bundle of wires was easily replaced with one fiber optic cable.
S / PDIF can also be found as a digital stream transmitter. Usually in this mode, DVD players work with the input of the AV receiver of a home theater. As a result, all new sound technologies have become available at home. Many users were able to get acquainted with the Dolby Digital and Digital Theater System (DTS).
Of all the options, the most common connector was RCA. He is paired with the S / PDIF standard "located" on consumer audio equipment. The optical type is used a little less often. To use an audio system with active acoustics, you just need to get the S / PDIF output.