An audio interface is basically a “go-between” hardware that connects different audio sources to a computer. The audio interface converts the collected analog sound signals into digital information that the computer can process and store. The same audio interface reconverts the digital audio files into analog signals for the various audio monitors and headphones. While the computer possesses an integral sound card, this sound card is, at most, only capable of handling single input/output that is insufficient in handling several audio sources that may include microphones for vocal or singing and musical instruments such as electric guitars.
Audio interfaces are designed to enhance the sound quality of different audio signals that need to be mixed. Audio interfaces are capable of separately transferring the collected audio signals to the computer for better mixing quality, and this functionality is vital to sound recording, mixing, and reproduction.
Generally, every audio interface brand has advantages and drawbacks. As a prospecting buyer, you must be aware of the interface’s compatibility with your computer, especially, with your home studio applications. Another factor when buying an audio interface is that you need to consider the purpose and usage of your audio interface to figure out the appropriate one to buy.
Table of Contents
- How To Set Up Audio Interface For Audio Recording
- Key Audio Interface Features to Consider When Buying One
- 1) Number of Input Terminals
- 2) Audio Interface Connectors
- 3) DAW Compatibility
- 4) Number of Outputs
- 5) The Form Factor
- 6) The Phantom Power
- 7) The Latency Factor
- 8) Understanding Preamps
- 9) Converters
- 10) Sample Rate and Bit Depth
- Audio Interface Comparison & Review
- Best USB Audio Interface for Home Studio
- Best Thunderbolt Audio Interfaces
How To Set Up Audio Interface For Audio Recording
Key Audio Interface Features to Consider When Buying One
The audio interface is manufactured and marketed either for personal use or more elaborate and comprehensive professional usage. Depending on the user’s requirements and whatever purpose the audio interface will be used, the most important feature of an audio interface is the number of input and output terminals that it possesses. In acquiring an audio interface, it is imperative that the prospective buyer knows most, if not, all factors that need to be considered.
1) Number of Input Terminals
The number of input terminals determines the usage of the audio interface. In most professional audio recording studios, inputs from multiple microphones, guitars, keyboards, as well as a drum set, are provided, enabling the user to segregate these multiple audio inputs. Audio interfaces designed for professional use may contain up to 24 individual input terminals using both 3.5mm and 6.35mm (quarter-inch) jacks, XLR sockets, and USB terminals. The audio interface is likewise, equipped with a variety of input terminals that can handle digital signals that include: MIDI, S/PDIF and ADAT terminal formats. Moreover, some audio interfaces are also provided with “combo” input terminals that combine three-pin XLR terminal with quarter-inch TRS jack into one socket.
Audio interface for home or personal use provides less number of input terminals as well as terminal types. In most cases, one or two physical input terminals like XLR and a line-live TS/TRS are sufficient for an individual to record voice or instrument altogether or separately. At its simplest form, an audio interface may possess two input quarter-inch TRS and TS input terminal and a smaller 3.5mm TRS output terminal for headphones.
2) Audio Interface Connectors
As mentioned above, the audio interface accommodates some different types of input as well as output terminals. These terminal types likewise correspond to the type of cabling and formats used. There are two types of transmission formats currently in use in audio production, namely, analog and digital.
Analog transmits its information through a stream of electric current while digital transmit its information in binary codes. In most cases, the digital format is the preferred format. However, despite the popularity of the digital over the analog format, the analog format persists and is still in use for some musical instruments.
There are three levels of analog signals—microphone and line levels which are balanced analog signals, and the instrument level which is an unbalanced signal. The two or three most common audio connectors are:
1)XLR or eXternal Line Return connector
The XLR or eXternal Line Return connector—are commonly used as connectors for microphones. This type of connector primarily consists of a male and female variant. The male variant is generally the output terminal while the female part forms the input terminal. The XLR has a circular profile having between three to seven pins. When used in microphones, the three-pin type is employed to transmit balanced analog signals. Moreover, a hybrid XLR/TRS input (female) terminal is also seen in some audio interface products.
2) TS/TRS phone jacks Alongside XLR—the TS/TRS phone jack
The TS/TRS phone jacks Alongside XLR—the TS/TRS phone jack is one of the most common input/output connectors found in audio interface. The TS (Tip, Sleeve) and TRS (Tip, Ring, Sleeve) can be readily distinguishable from each other as the TS sports a black band between the tip and sleeve of the jack while the TRS has black bands to separate the ring from the tip and sleeve. Like the XLR, the TRS is also used to convey balanced analog signals, while the TS jacks are mainly used on electric and bass guitars which transmit unbalanced analog signals.
In most audio interface products, there are several types of digital input/output terminals in addition to a number of analog input/output terminals. The wide variety of digital terminals allows the users to select the most appropriate interface connection to use. Some of these terminal types include:
- The MIDI or Musical Instrument Digital Interface—is generally used to connect and transfer various notes, velocity, and other musical information from the electronic keyboard/MIDI controller to the MIDI interface. The MIDI interface is in turn connected to the laptop or PC with appropriate DAW application or software. Currently, MIDI terminals are supplanted by USB as the USB is also capable of handling MIDI data.
- The USB or Universal Serial Bus—Despite being the slowest in data transfer rate at 12 Mbps on version 1.0 to 480 Mbps on version 2.0, the USB is the most cost-effective interface available. For home studios and users on a tight budget, the USB is the most suitable choice.
- The Firewire—A new interface connection between a computer and other peripheral devices, capable of transferring data at a higher rate and can be up to 800 Mbps on its latest version.
- The S/PDIF or Sony/Philips Digital Interface Format—S/PDIF is a type audio format used in the audio interface. S/PDIF commonly uses a coaxial cable with RCA jacks for connection. One problem with this type is that the digital RCA jacks look just as the older analog RCA phone jacks. Moreover, single cables capable only of passing mono audio signal are visually identical with coaxial cables that can handle stereo audio signals. However, the S/PDIF also uses the optical TOSLINK connectors.
- The ADAT or Alesis Digital Audio Tape—The ADAT, like the S/PDIF, is another type of high-speed audio format. However, ADAT has a dedicated interface connection that differs from other connector type and is capable of handling eight independent channels of digital audio.
Moreover, there is the USB microphone that doesn’t need a dedicated audio interface to plug into as this type of microphone has an integral interface and can be plugged directly into the computer’s USB port. Likewise, some musical instruments like the electric guitar with USB line out are also capable of being connected directly to the computer without the need for an audio interface. However, this process limits the number of sound sources that could be connected at the same time.
3) DAW Compatibility
In general, 90% of the DAW that is currently available in the market are compatible with most audio interfaces. DAW or Digital Audio Workstation is an electronic system or a computer application that is used for recording, editing, and producing speech, songs, music, and other audio files. The DAW is widely available as computer software for laptops and PCs. This configuration allows private users to record edit and produce their own audio file.
Professional DAWs, on the other hand, are integrated, a standalone unit with computer-controlled components. This DAW configuration is commonly used for indoor or outdoor performance or event coverage as well as for other commercial purposes such as sound editing, dubbing, and musical scoring for TV radio and film production.
In acquiring new audio interface, it is essential for DAW software users to investigate the compatibility of the interface with the existing software. There is, however, no abundance of websites from which you can verify the compatibility issues between software and the interface, and such verification information could be difficult to find. While most interfaces are compatible with any existing DAW software, the present compatibility between a DAW and an interface, however, can never be specifically ascertained in the future due to the current pace of technological development.
It is preferable therefore to have both the interface and software been manufactured by the same company and marketed as a “combo” product. However, not so many manufacturers offer this option.
4) Number of Outputs
Most users would probably hook two or three pieces of equipment to the audio interface’s output excluding those of the computers. This equipment may include a headphone/earphone or a pair of stereo speakers to monitor the sound that is being produced. Almost all interfaces are equipped with an output terminal for a pair of speakers or headphones along with a dedicated volume control for monitoring the voice or sound that needs to be recorded. In case of audio interface to computer connections, the USB is still widely used despite the introduction of newer types of connections like those of the Firewire or the Thunderbolt.
5) The Form Factor
The audio interface’s “form factor” simply refers to the equipment’s physical size and appearance. There are two basic forms of audio interfaces that are available in the market today, and these are the desktop and rack-mounted interfaces.
Desktop interface refers to the smaller audio interface variety that can be, as its name implies, placed on the top of the desk next to the computer. This variety is much easier to use and is most suitable for beginners or solo musical artist or performer. Moreover, this particular type is much cheaper and does not require additional space or mounts.
However, for more serious users who want to produce a band-sized performance, the larger rack-mounted type is the most suitable alternative as it offers a greater number of sound sources. Rack-mounted interfaces provide a much larger variety of ports to accommodate both analog and digital sound sources. However, due to its size, this type of audio interface requires additional space and a more comprehensive DAW software.
6) The Phantom Power
A lot of people do not really care about the types of microphones that they use. To many people, a microphone is simply a microphone. Who cares what type of microphone it is, as long as it serves its purpose? However, the reality is quite the opposite for there are various types of microphones. Some microphones are analog, while some are digital. Likewise, there are dynamic microphones that do not require power while some microphones require power to drive an active circuit or to polarize the plates of condenser microphones like those of the large diaphragm microphones.
Large diaphragm microphones are extremely sensitive in capturing amazing audio details and are much suitable for recording musical instruments without built-in sound-gathering apparatus like those of piano, drums, etc. These types of microphones are either powered by a battery or are powered by a device where the microphone is connected. In an audio interface, a 48V “Phantom” power usually supplies the necessary power for this type of microphones. Moreover, since not all microphones require “phantom” power unit, a switch is provided to the unit so that it can be turned “on” if needed and “off” if not needed.
7) The Latency Factor
In playing a musical instrument or in singing, it is quite noticeable if there is a delay between the creation of actual sound and its playback because this delay can be readily detected from speakers or headphones. This delay is called latency. This latency or delay can be very disconcerting to musicians who are playing electronic musical instruments such as that of the keyboard.
The problem of latency of computers has already been resolved and is not as bad as in the past. However, the computer’s standard sound card is still not up to the task of handling the speed needed in transmitting the audio data or signal. A dedicated audio interface, therefore, is needed to at least minimize this latency. At present, modern audio interfaces are capable of very fast transferring of audio signals from audio sources to speakers. Moreover, many modern audio interfaces are already equipped with zero latency monitoring devices or direct monitoring devices that directly allow performers or musicians to hear the sounds from their sources.
8) Understanding Preamps
Preamplifier or preamp is another necessary component of the overall audio interface set-up. Preamp boosts the weak signal making it strong enough for further processing without degrading the signal’s inherent noise ratio. The preamp, likewise, enhances the sound before it passes through the power amplifier to the speakers. Some audio interfaces have built-in preamps. However, more serious users usually prefer a separate preamplifier for better results.
A converter is basically a device that converts audio signals from analog to digital and vice versa. If a device can do this work and can simultaneously provide an “in” path for sounds to enter the computer and “out” path again to be heard, it is then called an “audio interface.” When all characteristics are found in one card, it is then called a “sound card.” Converters are usually integral parts of audio interfaces; however, some more meticulous users require a stand-alone A-D/D-A (analog to digital/digital to analog) converter unit.
10) Sample Rate and Bit Depth
After converting the analog “waves” into their digital forms, the real work of an audio interface begins. Audio interfaces work by “sampling” audio signals digitally at high frequencies. During the conversion process of analog to digital signal, the frequency wave is then “sliced” by an A-D converter into a thousand of pieces per second. The number of slices is measured in Hertz, and a thousand slices are 1 kilohertz or 1 kHz and are known as the sample rate. At a specific resolution, each slice or sample is digitally stored in a computer. Higher resolutions correspond to a greater number of bits that are used to represent each sample. This figure is known as bit depth. For example, the sample rate of a standard CD is 44.1 kHz, and its bit depth is 16-bit.
At present, a lot of commercially-available semi-professional audio interfaces have a minimum sample rate of 48 kHz and 24-bit bit depth. On the other hand, the sample rate of a professional audio interface can be as high as 192 kHz. While this level of sample rate can lead to prodigious audio quality, the corresponding audio file, however, will exert certain demands on the associated computer.
Audio Interface Comparison & Review
Best USB Audio Interface for Home Studio
1) PreSonus Audiobox USB 96
PreSonus Audiobox USB 96 or Audiobox 96 is an affordable desktop audio interface that is quite suitable for beginners and aspiring musicians alike. The Audiobox 96 features a two-channel, 24-bit/96kHz bit depth/sample rate. Upfront, the Audiobox 96 has two hybrid XLR/TRS “combo” terminals that can accept quarter-inch microphone jacks or XLR sockets. Likewise, it has a 48-volt phantom power switch, volume controls for two channels, a mixer, a headphone volume control, and a main gain. The USB port for computer connection, the MIDI ports, two quarter-inch TRS main output jacks, and a quarter-inch headphone jack occupy the rear. The USB also serves as the power supply from the computer. Moreover, a DAW software with third party contents is also included in the package. Lastly, the Audiobox 96 is compatible with either Mac or PC operating systems.