Audio Interfaces

Audio Interfaces take all the various audio inputs and convert them into digital audio data.

Though that sounds straight-forward, this was easily the most confusing part for me as I began the quest to design my own home studio.

This piece of hardware will end up being the front end for nearly all the inputs that will be used in your home recording studio.

Digital audio, electrical analog audio, and MIDI data will all come together in this great sonic melting pot.

It acts as the central hub for all the various Audio Signals in your setup... taking them from your finger tips and vocal cords and into the digital realm.

By handling all the audio input and output signals of your system it performs the same function as the Sound Card in a typical computer.

The main differences are that Audio Interfaces typically have mic preamps onboard, provide Phantom Power for condenser mics, and have easy-access external inputs and outputs.

So technically the terms Sound Card and Audio Interface could be used interchangeably.

But for our discussion let's define Sound Cards as hardware internally mounted to your computer, while a studio Audio Interface is an external hardware unit connected via USB or FireWire.

Though there are many options, there are 6 main features to consider when choosing Audio Interfaces:

  1. Analog / Digital Converters
  2. Number of Microphone Preamps
  3. Number of Inputs/Outputs
  4. Interface Type
  5. MIDI Capability
  6. Mixing Capability

Read on for a more detailed explanation of each criteria on our list.

You'll find many hyperlinks throughout this description that aim to supplement the discussion.

If this is all well understood to you, then you can jump to the chase and checkout my list for Top USB Audio Interfaces for Under $300.

For everyone else I strongly recommend having a firm grasp of the main issues that are outlined below before shopping for specific units.

This may be the single most important decision when creating your home studio, so it's critical to have a firm grasp of how these work and what they are used for.

1. Analog / Digital Converters

These provide the ability to take the electrical signal from your microphone or instrument and convert it into the digital signal that computers can understand.

Just as Doc Brown needs the Flux Capacitor to make time travel possible... so do we need A/D converters to make digital recording a reality.

Audio Interfaces are the quickest and easiest way to introduce this essential component into your setup.

A/D converters are described as a set of 2 numbers: a bit depth (i.e. 16-bit, 24-bit) and a Sampling Rate (such as 44.1 kHz, 96 kHz, etc).

This set of values represents the maximum bit depth and sample rate possible with a given interface, you can always set them lower as you choose.

A bit depth of 24-bits and sampling rate of 48 kHz are solid target values to shoot for when shopping around.

A common mistake is to assume that a mixing console will provide this capability, but unless it has a USB or FireWire output it will not.

Furthermore you'll have to pay top dollar (~$1500) for a digital mixer with the ability to record each input to it's own dedicated track, something even moderately priced audio interfaces can provide.

The more affordable digital mixers (~$300) will only output the Left/Right main outputs through the USB or FireWire interface.

Check out our Analog / Digital Converters Page for more info on this fundamental building block of your studio.

2. Number of Microphone Preamps

These guys take the relatively low mic-level output signal and boost it to a usable level.

When choosing this piece of your rig, a critical consideration is how many individual microphones you plan to use.

You will need a mic preamp for every mic you want to record at the same time!

You will also need one of these for every mic level signal (such as the one coming out of a direct box) that you plan on recording.

For example, if you want to record an electric guitar & bass via direct boxes with 2 mics for vocals - you will need a total of 4 mic preamp inputs.

This will allow you to record each instrument and vocal on a dedicated track on your DAW Recording Software at the same time. This is a big deal.

Why? Because it gives you the ability to alter the level, assign processing FX, and generally edit each input without affecting the others in your mix.

But are these built-in mic preamps any good? Or should I buy individual mic preamps instead??

The onboard Mic Preamps found on the commercially available audio interfaces I discuss on this site are quiet and powerful enough to make beautiful recordings with.

You do not need to spend a king's ransom buying these individually, even though that is an option you may consider at a later time.

I'd recommend against this until you have some more experience because it does get a bit more complicated, and it's more than you need to worry about starting off.

Mic preamps tend to get swallowed up quickly so err on the side of getting an interface with a few more than you think you'll use.

After considering the number of mic preamp inputs you need, the next question is how many other inputs and outputs will you require.

3. Number of Inputs / Outputs

Some instruments like keyboard synthesizers and drum machines can be added via a line level input.

These are different than the mic inputs listed above because these instruments' output levels are much stronger than the tiny output signals that come from microphones.

Line level inputs can come in 2 different flavors:

One accepts the input for a 1/4" instrument cable only, and the other is known as a combination (or just combo) jack that can take either a 1/4" instrument or XLR cable input.

The combination jack is becoming very popular because of its versatility, but it's also slightly more expensive for manufactures to produce so don't look for them on the entry level budget units.

Just like the mic preamps above these get eaten up fast, especially if you have a left / right output such as that from a digital piano or drum machine.

On the output side, all units will have at minimum a stereo main out.

Some units may have multiple additional outputs that can expand the possibilities of your home recording studio setup.

Additional outputs usually come in stereo pairs and are useful for sending specific tracks to outboard (hardware based) effects or to a custom headphone mix via a Headphone Amp.

Even in the higher priced units, the number of outputs can vary drastically, so make sure you consider this carefully when choosing one.

4. Interface Type

The interface type defines the protocol for transmitting digital data between the audio interface unit itself and your computer.

This is where the rubber meets the road. The 2 options here are USB & FireWire.

Obviously if you choose an interface that uses a FireWire input, you will need a FireWire card on your computer.

Nearly every computer (both Mac and PC) has USB inputs, while FireWire is usually seen only on Macs.

USB is simply more common and there is no significant difference between the two, and the newest interfaces today support the USB standard - so FireWire's days may be numbered.

The transfer speed of each is more than adequate to handle the typical home recording session.

The only way you'll reach the limit of your data transfer rate is if you do something crazy like attempt to playback a 60 track project during mixing.

For most smaller scale operations any interface will work fine. Don't get too caught up debating between the 2 types.

Check out our USB vs FireWire Page for a more complete look at each option.

5. MIDI Capability

If you're considering adding MIDI capability to your home recording studio then this is a great place to address it.

Unless you have several MIDI devices that need multiple inputs, you can include MIDI in your setup here without having to get a specialized piece of gear.

Some of you may have several MIDI instruments that you want to hook up simultaneously (Synth-aholics Anonymous may be in your near future).

If this sounds like you, you'll want to explore a dedicated MIDI Interface with multiple inputs / outputs.

In other words, the included MIDI inputs on nearly every audio interface will likely be inadequate if you need more than 1 MIDI input and 1 MIDI output for your studio.

The good news is that it's often included so even if you're undecided on the whole MIDI thing it won't cost you any extra to have the option to play around with it.

Most newer MIDI controllers can also be connected to your setup via USB as well, so this can be another option for adding MIDI capability without the standard MIDI I/O.

That brings us to the final piece of the puzzle, mixing capability.

6. Mixing Capability

Audio Interfaces sync with digital mixing software to allow you to alter your tracks in the same way that a physical mixing console does.

Instead of actually turning a physical knob or fader however, you adjust virtual knobs and faders with your mouse through your associated recording software.

It's also possible to use a separate mixing console in conjunction with an AI to provide a hardware mixing capability.

I don't recommend you do this, though, because it can get confusing in a hurry, plus it's another piece of expensive gear which can take a big hit on your budget.

This caused me all sorts of trouble when I started out, not understanding if I needed a mixer or not for my young home recording studio setup.

Just to make it very clear...

You Do Not Need a Hardware Mixer to Record Music!

Mixers might best be left to live scenarios when you need the mic preamps for amplification purposes only.

For those who feel a physical knob to turn would be easier, better, or just more fun... check out the Control Surfaces Page for more info on how to make that happen.

A control surface will allow you to turn a physical knob (similar to the controls of a dedicated mixer) to adjust the software mixer on your computer.

Whether you choose to use a control surface as an external controller or simply use your mouse and keyboard, the audio interface will interact with your software to provide all the mixing controls you'll need for your project.

Still having trouble choosing between different models to fulfill the needs of your home recording studio??

Check out the following Audio Interface Buying Guide to see popular models compared side by side.

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