S / PDIF - what is it?

To date, there are so many slots and connectors that it is sometimes difficult to deal with one of them. So, often there are problems with the purchase of a new device and the connection to it of some additional devices. Today we learn all about S / PDIF - what it is, what for and why.

The concept of

Interestingly, the international standard allows you to use the option of both S / PDIF and S / P-DIF. He has his own transcript, which gives 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 transfer digital audio from the first audio device to the second.

Considering S / PDIF, we will deal with its physical and system part. The physical parameter makes it possible to find out which way the signal is transmitted and by what channels, and the system one - which protocol is used.

Specification

Before you understand the scope of this interface, we will understand what it does. In general, this format allows several types of cables and connectors. So the world is available digital S / PDIF, coaxial and optical. There are suitable adapters and adapters for these all variants. It is possible to use optical instead of coaxial and vice versa. The only thing is that, in addition to adapters, you need an external power supply.

Ancestor

The development of this interface began with the AES / EBU professional standard already available. Cipher for the first time became famous in 1986. Then the Society of Sound Engineers and the European Broadcasting Union worked on it . The revised version was used in 1992, after which it underwent changes in 2002 and 2009.

As usual, there is some difference in interfaces. It can be determined with the help of established standards.

Difference

If you do not know anything about S / PDIF, what it is and what you need, then you probably never heard of AES / EBU either. The latter standard was invented for DAT and CD formats, which are encoded using impulse-code modulation. The interface uses the BMC code. This means that the transmission of information occurs with any index of the sampling frequency, and the frequency recovery passes through the decryption of the data.

The AES standard was represented by three modifications. All worked with a resistance of 110 ohms, with a symmetrical connection, depending on the modifications, a shielded pair or category 5 cable was used. The connector standard also differed, first XLR or D-25, later RJ-45. Signal level 2-7 V.

The modulation remained unchanged and passed through the coding. Subcode data is represented by ASCII ID-text. The maximum distance was initially only 100 m, later - 400 m. The resolution reached 24 bits.

Before everyone knew about S / PDIF, what it is and what it takes for, an intermediate version of AES3id appeared. It already worked with a resistance of 75 Ohm, the connection was asymmetrical, the cable was coaxial. The format of the connector again changed to BNC, and the signal level dropped to 1 V. The maximum distance reached the mark of 1000 m. The resolution remained unchanged - 24 bits.

This intermediate version largely dictated the specification of the novelty. So, the monitored standard also worked with a resistance of 75 ohms, had an asymmetric connection. The cable was both coaxial and optical, depending on the type. The connector again changed the format: RCA or TOSLINK. The signal level became less than half - 0.5 V. The subcode data was changed, which was equipped with SCMS copy protection technology. The maximum length decreased and became only 10 m, and the ability of 20 bits optionally showed all the same 24 bits.

Types

As we said earlier, there are three types of this standard. There is an optical S / PDIF, digital and coaxial. The first TOSLINK got its name thanks to the developer of Toshiba. This is a fiber optic standard. It can often be found in consumer audio devices, computer sound cards, etc. Popular recently are MiniTOSLINK with 3.5-jack form factor. They can be found in some models of laptops, in which the S / PDIF output is combined with a headset.

The coaxial type has a resistance of 75 ohms, is connected via the RCA interface. If you do not fit conventional audio cables, which are also called tulips, then take a closer look at the coaxial standard. To work correctly, it terminates on both sides, and the input and output impedances are 75 ohms.

Digital audio S / PDIF - the third type, level-by-level (TTL). The standard is based on a bipolar scheme for building transistors and resistors. Transistor-transistor logic is based on two stages, though not always. The first one is 2.4V, the second is 0-0.4V. Outputs of this type can be found on sound cards.

There is a simple explanation of the classification, so as not to be confused and properly deal with what it is - S / PDIF. This digital audio interface, as we have already discovered, can be digital or optical. If you have a good audio system or a sound center at home, it's best to connect it through this type of connector. The sound quality is much better than the standard format.

The improvement is due to the fact that the sound, passing through the high-frequency stuffing and collecting all the "dirty" pulses, is not output through the analog format, but digital, which does not make the sound distort. If you use the optical standard, you can forget about the noise on the general drive.

Application

The surveyed standard was first used in CD-players. Afterwards it was found that it can be used as a connector and transmitter of sound in other audio devices. So, this interface began to appear in MiniDisc-players and on sound cards for PC. Some observant drivers could notice the standard in automotive sound. Especially it has become a godsend for those who are tired of the disorder 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 are used with the AV receiver of the home theater. As a result, all new sound technologies became available at home. Many users could get acquainted with Dolby Digital and Digital Theater System (DTS).

Of all the options, the most common connector is RCA. It is paired with the standard S / PDIF "located" on consumer audio equipment. Slightly less often, the optical type is used. To use an audio system with active acoustics, you just need to get an S / PDIF output.