Audio interfaces transmit audio signals from peripherals to PCs and vice versa. They basically do the same thing as one sound cardwhich is already standard on most PC’s, often as „on board sound“ on the PC motherboardintegrated. This is often enough for streaming YouTube videos or occasionally listening to music that does not have very high demands on the sound. However, the limits of the application possibilities of a simple sound card are quickly reached if music is to be actively produced by oneself. Then it turns out that the sound quality of a sound card is usually not sufficient. In addition, a circumstance often makes disturbing, which bears the name „latency“. This refers to the speed at which audio signals are input or output. Short latency is required when an external audio signal, e.g. From one Keyboard, in the PCarrives and from there on speakeris output. This should be done with inaudible time delay to ensure smooth timing. Standard sound cards are often overstrained and, moreover, usually do not provide enough input / output channels.

Basic operation of a Audio Interface

Audio interfaces are designed for use in the professional or semi-professional field and for high demands on sound quality and miscibility of audio signals. They usually include flexible drivers, high-quality converters and a large number of connection options, with the number of audio inputs usually being higher than the number of outputs. Several external audio sources or audio output devices can be connected and operated simultaneously. The interfaces allow you to record, edit, transform, mix and output audio signals.

The connection to the computer

In general, a distinction is made between internal and external devices. Internal audio interfaces installed in the PC are designed for direct connection to the PCI or PCI Express bus. However, most devices, especially in the high-end segment, are external audio interfaces in their own housing. The data transfer to / from the PC or laptop / netbook takes place via standard connections such as USB, Firewire, PCMCIA / PC Card, and ExpressCard. Solutions with Firewire connection are becoming increasingly popular because this interface is suitable for large volumes of data with good transmission stability. In addition, there are Thunderbold connections to the computer. But they are more of an exception.

Connection options to the periphery

For peripherals such as u. a. Keyboards, guitars, microphones, headphoneand speakers have analog and digital connection ports. The latter can be found especially in professional devices. Frequently encountered interfaces include:

– S / PDIF (Sony / Philips Digital Interface)
Interface specification for both electrical and optical transmission of digitized multi-channel audio signals.

– ADAT (Alesis Digital Audio Tape)
Originally designed for magnetic tape recording, ADAT is now standard in small and medium-sized recording studios for the transmission of digitized audio signals over optical fibers.

– AES / EBU (Audio Engineering Society / European Broadcasting Union) refers to a specification for interfaces for the transmission of digital audio signals in stereo, two-channel or mono technology.

– MIDI (Musical Instrument Digital Interface)
This interface is an industry standard for timing musical control information. Main application area is the connection of keyboards and synthesizers, A connection of other musical instruments is generally also possible, for. As electric guitars, but forms an exception.

Housing designs and operation

The types of audio interfaces are diverse and disadvantageous for different applications. Purely stationary devices are available in 19-inch dimensions for installation in a corresponding rack. Other devices are stationary in a box or box-like housing to operate, which is also portable. Some interfaces have rotary potentiometers on the front and a display for level metering. In addition, there are also hybrid interface mixer designs that offer the advantage of having multiple interfaces in a single enclosure. The same can be done with single devices, since many interfaces are cascadable.

Common features and some hints

Some audio interfaces have their own processor and a hard disk integrated in their case. Stand-alone mixing is possible on some devices. If the number of input / output channels is insufficient, the possibility of cascading can be used with many devices in order to expand the number of channels with multiple interfaces. In such a setup, however, should first check whether the audio program on the PC is compatible, which is not always the case. Generally, it should also be checked before purchasing an audio interface, whether the desired combination of interface, PC chipset, operating system and audio software is executable. Forum pages of the manufacturers often provide information. Furthermore, attention should be paid to the required version of the frequently used ASIO (Audio Stream Input / Output) driver.