Despite the availability of all-in-one devices like field recorders and mobile phones. I am still heavily partial towards the use of a discrete audio interface. For starters, they are able to process audio at much higher resolutions. They also allow the use of any microphone you already have as nearly all audio interfaces for the past 5-7 years are already able to provide phantom power and hi-fidelity amplification. A discrete audio interface has multiple input and output ports which enable itself to be the hub for multiple audio devices in your workstation and make them work properly.
With that said, whether or not you need an audio interface, or how big of an interface you need entirely depends on your workflow. For example, occasional voice recording would make having an interface excessive. A more regular podcasting project, interview, or solo performance recordings would do well to have an interface with two mic/line inputs. An acoustic duo might need at least four inputs, while recording a full band setup that includes a fully mic’d drum set might require at least 16 inputs.
There are a lot of audio interfaces to choose from, but below are some of the points that you will need to consider”
- Power input – most 2-input models can be powered through USB, making setup simpler. However, larger models will require a separate power supply. If this has an impact over your work flow, keep it in mind.
- Connectivity – an audio interface will typically come with either USB or Firewire. One is affordable and more universal and the other is considerably faster. Newer hardware are also starting to support Thunderbolt. You will have to decide what is more relevant to you. One thing I do have to note that just because Firewire is faster doesn’t mean that USB is not fast enough.
- Resolution – it would be best if you get an interface with a minimum bit depth of 24 bits and sampling rate of 48KHz. Higher values are nice to have, but may not be necessary.
- MIDI – some interfaces have MIDI connectivity, which may or may not be useful to you.
- Phantom Power – as mentioned, all new models can supply phantom power. But you might come across with older ones that don’t. Avoid buying these.
- Bundled software – some come bundled with potentially useful software, particularly DAW plugins.
- System compatibility – as evidenced by upgrading Windows 8 to 10 or OS X Yosemite to El Capitan rendered system drivers incompatible, rendering the hardware unusable until new drivers are released. Unfortunately, sometimes it takes a while for manufacturers to do so. And that is for current models. Old models might not even have the benefit of new drivers.
The Focusrite Scarlett is a popular line of USB audio interfaces, while the Saffire series from the same company support Firewire. Pro Tools users are often locked in with Avid hardware. Other devices you can consider are the M-Track series from M-Audio or my personal favorite, the Roland Capture series.