An audio interface is comprised of a hardware box or unit separate from your computer system that permits the input and output of sound to and from your computer. Part of it may also come with your computer, or be in-built, such as the case of a separate or default sound card. You may also use a hardware box with various kinds of plug-ins, such as quarter-inch phono plugs, RCA connectors for a cassette tape deck, and the more sophisticated XLR connectors used with high-end microphones.
 
The separate hardware unit may also be likened to a mixer, wherein the audio interface works with pre-amps and analog input methods. After the signal passes through the pre-amp, it is transformed into digital data, and transmitted to the computer by way of a digital output. Related software then translates the aforementioned data and sends it back to the audio interface. The interface can then reconvert it to analog format before playback. There are also various kinds of analog to digital and digital to analog conversion units (which were utilized in the signal translation process).
 
Here are some types of interfaces that focus on audio:
 
• the Audio Codec 1997, or AC97, which allows for transmission between ICs (Integrated Circuits) on motherboards from PC systems
• the ADAT interface
• the AES / EBU interface using XLR connectors
• AES47, utilizing the AES3 digital audio format for networks with ATM or Asynchronous Transfer Modes
• Bluetooth using A2DP
• I²S or Inter-IC Sound interfaces for ICs in products for the consumer electronics market
• the Multi-channel Audio Digital Interface, or MADI
• MIDI interconnections for low bandwidths that carry data (but not sound)
• S/PDIF through TOSLINK or co-axial cable systems
• TDIF using the proprietary TASCAM format for D-Sub cabling
 
Digital bus devices, such as FireWire, PCI, and USB-technology powered tools can store information in the digital audio format as well.
 
Digital Audio Conversion
 
What affects sound quality in your audio interface or sound card? Two integral parts of your sound card or audio interface dictate sound output quality. Default software drivers that come with the acquisition of the card is one, while the second is the DAC, or digital audio converter incorporated into the card itself. The microphone pre-amps of your audio interface can also influence the quality of any recorded data.
 
Choosing between an Audio Interface or Sound Card
 
As recent technological developments change sound cards and audio interfaces, many professionals are biased towards one option. Musicians and sound technicians generally go for audio interfaces rather than conventional soundcards. These interfaces may be based on FireWire or PCI technology. The audio interface usually includes a breakout unit or box, which stands separate from the main computer. The audio interface also uses a cable attached to the computer’s PCI card, or a connection made with FireWire or USB-type cables. The breakout box has ports where instrument cables, mixer cables, monitor cables, or microphone cables can be affixed. The standard soundcard is typically located in a PCI slot within the computer, where the cables are at the rear of the said card.
 
A large portion of the sound cards being sold today have decent DAC capabilities. This is a far cry from just some years ago, where a user was required to pay a high price for good digital audio conversion. The evolution of digital audio conversion systems can be compared to compact-disc player technology. The first CD playing systems usually resulted in tinny or hollow-sounding output. Eventually, sound engineers and specialists refined DAC by error correction, interpolation, oversampling, and various methods to hone the sound. Sampling is the nucleus of the digital audio conversion process. The converter decodes the forthcoming analog signal and translates it into data. Once the signal had been completely transformed into information that the system can handle, the computer can then administer it by combining it with separate data, storing it on the hard drive, etcetera.
 
The quality of digital audio conversion is directly proportional to the condition of output from the card. The type of card (be it FireWire, PCI, or USB-based) does not dictate the sound output quality. The technology used simply serves to transport, transmit, or hold the data. The DAC is what actually shapes the sound, if you will. It is the main aspect that influences sound output quality.