The simple definition of an audio interface is as a synonym for the term sound card. This is a piece of hardware present in computers and other devices that both outputs sound from a computer, via loudspeakers or headphones, and inputs sound from external devices, such as a microphone, to a computer. They can be internal and connect to a PCI or other slot inside a computer or external and connect to a computer via a USB or Fire Wire connection. These external forms are what are most commonly referred to as audio interfaces.
In fact, audio interfaces are more accurately described as sound cards specifically designed for the use in sound and music production. They both input and output higher quality audio reproduction.
Initially, they were developed to solve the issue of latency in the recording of audio. The time it took for an audio signal to be sent from an external device to a computer created a delay. This meant certain audio recordings were out of sync with other parts of a recording. While the latency issue has improved since the introduction of early sound cards, it can still be an issue, especially with internal cards. These external audio interfaces eliminate latency to such an extent that it’s unnoticeable.
Both sound cards and audio interfaces have sockets for various input devices. The most common form is a microphone. However, audio interfaces have more sockets and this allows for multiple instruments to be plugged in and recorded at the same time. Each input can be set to record to a specific track in audio recording software. This allows for specific instruments to be fine-tuned. Interestingly, these devices normally include sockets for MIDI devices to connect to. You can find out more about MIDI and MIDI devices in our article here.
The type of audio interface a person will purchase depends on their needs. A singer songwriter would probably only require a model with a small number of slots to connect a microphone and an instrument. However, a full band would need many additional slots.
Mixers and Virtual Mixers:
These are devices which take two or more audio signals and combine them to generate one or more output signals, normally in the form of two stereo channel output. They come in many shapes and sizes. The traditional versions are known as sound desks or sound consoles. These are the large panels with hundreds of dials on them that you often see in pictures or videos of recording studios. There are also much smaller hardware based versions available and purely digital versions that run and operated on a computer.
In the hardware versions there are slots for connecting the devices which are to be recorded and mixed. There are various controls under each input socket that control the audio input of that particular device. Each individual set of input sockets and controls is called a channel—the bigger the mixer, the more channels available.
The audio from a device enters the mixer and is adjusted by the various dials and effect controls. It is then normally sent from the channel to the main mix. However, it isn’t uncommon for a number of channels to be sent to subgroups. A subgroup is a compilation of various channels. It’s extremely useful for combining elements like separate drums into a single channel because it places them under a single set of controls rather than having to fine tune each element individually.
There are also auxiliary channels. These allow for signals from multiple channels to be sent to another output destination (such as a monitoring unit) while still been sent to the main mix or subgroups through their current channel. An auxiliary channel is the combination of all the auxiliary signals been sent to it. The more advance the mixer, the more auxiliary channels usually available.
The various dials allow engineers to adjust levels and enhance the sound of a particular channel via the use of effects and equalization.
Here’s a summary of sum of the most common controls and features:
- Input Gain: This effects the volume level of the channel before it interacts with the rest of the channel controls.
- Phantom Power: If active, this sends a DC voltage back to the input device in order to power it. This is a common requirement for microphones.
- Equalization: This increases or decreases certain frequencies in a signal. It is used to reduce feedback, correct unnatural sounds in a signal and make the sound more clear. More basic mixers provide a treble and bass dial under this heading that control a band of higher frequencies (HF) and lower frequencies (LF) respectively. The more advanced mixers have multiple dials (parametric equalizers) in order to fine tune specific ranges of frequencies.
- Panning: This controls how the audio from a particular channel will be heard through left and right speakers. It allows for a signal to be played through left and right speakers at the same level, one specific speaker on its own or more dominantly in one speaker than the other in the final mix.
- Mute and Solo: A channel can be set to mute to stop the input signal been sent to the final mix. It can also be set to solo which means only that channel will be sent to the final mix.
- Reverb: Affects the acoustics of a signal and can make it sound further away or closer.
- Chorus: This effect essentially doubles up the signal as if there are two or more sources producing the same sound.
- Delay: The signal can be set to repeat a number of times after a certain period of delay. This creates a sort of echo effect.
- Compression: This lessens the dynamic range of loud and quiet sounds by reducing the volume of loud sounds and amplifying the volume of quiet sounds.
- Slider: This controls the volume of the signal after all the various controls and effects have been applied.
Hardware mixers are becoming more uncommon in home recording. This is because people can record their various parts on to a computer using an audio interface and mix them together at later point in a virtual mixer—a piece of software or part of a piece of software that mimics the features of a hardware based mixer.
Sequencers and Digital Audio Workstations (DAW):
A sequencer records audio and MIDI input allowing it to be edited and played back at a later time. In its most basic form it’s quite simply a device which can record and play back audio. For example, a keyboard with a record function technically contains a sequencer. In their more advanced form, they’re the foundation of music production. They allow for the separate components of a song to be recorded on what are called tracks and edited together with other components.
These more advanced forms were a common feature of audio mixers. However, with the increase in computing power they’re more often run on a computer in today’s world. They’re part of Digital Audio Workstation software, which is commonly abbreviated DAW. This software combines sequencing, mixing and a whole host of tools such as virtual synthesisers, samplers and effects panels under a single hub. This is where the data recorded via a sound card or audio interface is normally sent.
Theses DAWs provide a plethora of advantages over the old hardware based sequencers. In fact, many of these old hardware based sequencers actually lack the ability to undo actions. In the past, if a mistake was made it could mean needing to record that section again, but now it’s as simple as hitting the undo button. The power to cut, copy and paste have also made the process much simpler. It’s possible to drag and drop entire sections into wanted positions and use keyboard shortcuts to quickly and efficiently achieve certain tasks.
They also provide additional features such as looping, quantization, randomization, and transposition, which further simplify the arranging process.
The ability to save and transport files easily between different computers and over the internet has also made it easier to have multiple people work on a piece from various locations.
These are loudspeakers specifically designed for audio production. They’re designed to produce flat phase and frequency responses. This means they don’t increase or decrease certain frequencies distorting the true tonal qualities of the source audio. They’re positioned so the audio produced goes directly to the person listening to ensure the signal doesn’t bounce off walls and surfaces and become polluted.
Normal loudspeakers bend certain frequencies in order to create a more pleasing sound. This is problematic when recording material. The producer needs to hear an accurate representation of the audio in order to pick up and eliminate undesirable tonal qualities. This means the eventual song will translate well on to home based speakers.
Another issue with consumer based speakers is that the raw audio produced in a studio setting can destroy them. This is because they are only designed for playing back sounds mastered with in a standard dynamic. Studio monitors are designed to withstand the demands of studio audio.
In this article we’re discussed a range of hardware and software related to music production. This has, hopefully, provided some clarity to those new to music production or those simply interested in the topic. It’s important to note, while an individual interested in producing professionally might need a combination of the hardware above, a DAW is all that is necessary to start making music at home with a modern computer.