Without a doubt, the audio interface is one of the most important recording tools, as it is, next to the audio computer, the central element of a modern recording studio. Whether mobile recording, live recording, home recording or band recording, project studio or bedroom production - audio interfaces play a major role as a bridge between analogue and digital, not only in technical terms but also in terms of sound.
The question is: How much audio interface do you actually need? There are audio interfaces in a wide variety of performance and price classes - as external rack and desktop devices or as sound cards for installation in an audio computer, for different interfaces and as complete solutions with an extended range of functions such as monitor controller, digital mixer, on-board DSP effects, audio network. But it doesn't always mean that the most expensive has to be the best audio interface. And before you spend too much money and buy performance that you may not need, you should check which features you really need for your recording applications and which range of functions an audio interface really has to offer for daily work.
One thing should be remembered in any case: Audio computers come and go, but an audio interface is usually used for much longer. The power of current computers is constantly increasing. Every two years or so, a new system comes onto the market that far surpasses the performance of the old generation. At the same time, the performance requirements of music software are also growing. More DSP power, more memory, faster data transfer - all factors that DAWs and VST plug-ins like to use for even better sound characteristics of effects and instruments. Therefore, when buying an audio interface, you should keep compatibility in mind: Will an audio interface also be up-to-date when switching to a new audio computer? If you change your computer platform, will the interface be compatible with it? An example would be FireWire - although the port is aging, it is still in use. But hardly any current computers are equipped with it, so you have to resort to adapters and similar solutions if you want to continue using the old interface.
USB audio interfaces are currently the most common - from the mini version for on the road with stereo inputs and outputs to the multi-channel interface with 16 inputs and more. The American manufacturer MOTU has even broken the previous limit of 16 audio channels with USB 2.0 drivers for its current audio interfaces. Nevertheless, USB 2.0 is already one of the older standards. Current interfaces such as USB 3 and especially Thunderbolt are much more powerful. But you only need an audio interface like this if you need to be able to stream a lot of audio at the same time. This is the case if you want to operate many audio inputs and outputs in parallel - e.g. for a complex live recording with 24 tracks or a larger project studio in which you do band recording. Basically, you can say that the power of Thunderbolt and USB 3 is needed if you want to transmit significantly more than 16 channels via individual audio inputs and outputs simultaneously. For home studio applications, songwriting and classic bedroom productions, a USB 2.0 audio interface is perfectly adequate.
Audio interfaces and DSP boards from Universal Audio are a special case: Here, special plug-ins are calculated by a DSP board - this relieves the computing capacity of the audio computer, but at the same time places higher demands on the performance of the audio interface. A good example of this is the Apollo Twin audio interface: As a classic audio interface for desktop recording, the number of inputs and outputs is manageable, but for the calculation of the UAD plug-ins, two complete audio streams must always be taken into account: from the DAW to the UAD plug-in and back to the DAW. With stereo signals, this means four audio channels that are exchanged in parallel via the interface between the audio PC and the audio interface. With this audio interface, the number of audio inputs and outputs is much less important. The calculation works out much more like this: The more UAD plug-ins are used for the mix at the same time, the greater the performance demands on the audio interface.
If you are looking for an audio interface for home recording, you should look for practical all-in-one solutions for desktop recording. Because here you get everything that a large studio offers in terms of functionality and workflow in a small format. In most cases, instruments such as electric guitar and bass can be connected directly to the audio interface via an appropriately designed audio input (Hi-Z). There is also an XLR jack with switchable phantom power for connecting condenser microphones. Here you should check whether the audio interface is bus-powered - i.e. draws its operating current via the USB interface - or whether it requires a power supply unit. With the latter version, you can generally assume that the phantom power reaches the prescribed 48 volts. And if you want to connect your studio monitors directly to the audio interface, you should make sure that it is equipped with an integrated monitor controller. In addition, at least one headphone output with separate volume control is required.
Incidentally, if you want to change computer platforms or have to switch to a different computer in other studios, the hybrid audio interfaces from MOTU are interesting, as they serve two ports at the same time - e.g. Thunderbolt and USB 2.0, so you have maximum flexibility. With audio interfaces that use USB 2.0, you can usually assume that they will run on a PC and Mac, and often without installing special drivers - plug & play. Many audio interfaces are also iOS-compatible (class compliant) and can be connected to the iPad or iPhone either with the help of the Apple Camera Kit or in some cases even directly via the Lightning cable. An audio interface with remarkable compatibility is the iConnectivity iConnect AUDIO 4+ or iConnectivity iConnect AUDIO 2+. It not only enables the simultaneous operation of two audio computers via USB 2.0, but also allows the direct connection of iPad or iPhone. Furthermore, this audio interface enables flexible audio routing, whereby the audio streams can be networked between two different computer platforms.
External audio interfaces have become more and more popular, but sound cards for installation in the audio computer are still available. Here, too, there is a large selection. An external audio interface is more flexible - it is much better suited to recording setups that are based on a laptop and, above all, are intended for mobile use. Permanently installed sound cards are available in a wide variety of designs, whereby the connection with the other audio devices is made via the corresponding rack front-end or also break-out cable whips or break-out boxes. Sound cards for installation in the audio PC often do not even offer analogue audio inputs and outputs, but provide interfaces for special converters - e.g. in ADAT format - or are designed for connection to audio networks (MADI or Dante).
Akai, Alesis, Antelope, Apogee, Audient, Avid, Behringer, ESI, Focusrite, Hercules, iConnectivity, iCON, IK Multimedia, Line 6, Mackie, Metric Halo Labs, MOTU, Native Instruments, RME, SPL, Steinberg, Tascam, Universal Audio, Zoom