The choice of the audio interface

With this article I try to help anyone thinking about buying a digital audio interface. During my career, both as a producer as a musician, I have had to face with the dilemma of choosing the interface that would be appropriate for every situation, and I have used different types as I have evolved professionally. I have bought or recommended devices for studios, sogwriters, portable studios, bands, mastering studios, etc..

An audio interface (also known as “sound card”, “audio card” or “recording interface”) is a devices that allows us to convert sound waves into digital data capable of being processed by computers and vice versa (see “Quality of digital audio in computer music” for more information)

Let’s see what types there are, what are the critical features and some examples of the most common situations when deciding.

Types of audio interfaces

Today the market offers a huge variety:

Internal sound cards: we are talking about those designed for professional audio, and which require an internal connexion to the PCI or PCIexpress bus.

External sound cards: to be externally connected via a USB, FireWire or Thunderbolt ports, making the installation much easier and ensuring a more comfortable access to different inputs, outputs and controls.

Interfaces for notebook: small devices with few inputs and outputs designed for easy connection (USB key, PCMCIA slot, etc …) and easy transport along with a laptop.

Mixers with built-in interface: mixers that incorporate the audio interface, with an USB or FireWire connexion to exchange information with the computer. We can say that there are three types:

• Mixers that only send and receive the stereo mix.
• Mixers/controllers that send and receive all tracks, and manipulate the audio digitally
• Mixers that send and receive all tracks, and manipulate the audio analogically

Digital multitrack recorders and other interfaces: there are digital multitrack recorders that incorporate the option to be used as audio interfaces. There are also usb microphones, usb guitars and other instruments with an audio interface incorporated.

Important features to be considered

Once you choose the most convenient type of audio interface, we will study some key features to choose among different brands and models of the same type. Are presented and briefly explained below.

Audio Quality: is the most critical point, and where we should pay more attention, if we want to ensure that the quality of our recordings are not affected by the interface.

Number of inputs and outputs: depends on our needs, the type of music that we are recording (singer, hip-hop, electronics) and the way we are going to do it (by tracks or the whole band playing at once). Beware of advertising because more times any audio connection is counted as an input/output audio connection.

Monitoring and headphones: Sometimes it is desirable to have more than one.

Other less important considerations: type of connection, operating system, proprietary hardware (which requires the use of a particular software), MIDI, digital inputs/outputs, standalone, concatenation, effects.

A computer audio interface for each user

I set out below most common situation with examples of the device to choose and the features it should have.

Songwriter, composer, or hip-hop recording at home: is this case the normal is go recording each instrument separately, at most in stereo, so it will be enough to have an easy to transport device with two inputs, an I/O MIDI port, an stereo output and a headphone output. If you want to go a little further in terms of recording quality, using different signals to get different nuances of the same instrument (using more than one mic and direct inputs), you might prefer to have 4 inputs and 4 outputs.

Band recording in rehearsal: the number of entries more common for larger interfaces is 8, which can be perfect for recording all members of a band playing at once. We’ re talking about an interface with 8 inputs and 8 outputs, portable and capable to work in standalone mode so it can be carried to the stage.

Recording studio and production: since this must be the most demanding case, let’s make some considerations of minimum essentials: high quality of inputs and outputs, rates of 48kHz and 24 bits, at least 16 inputs/outputs, more than one headphone output, digital inputs and outputs of all types, MIDI inputs and outputs and effects (eq, compressor, reverb, etc …). We are talking about PCI cards, rackmount devices or mixers with a built-in interface.