The world of music production has seen many changes in recent years. Traditionally, production of music would have been carried out in purpose-built recording studios, but nowadays, the production of electronic music is often accomplished using a PC or Mac computer, sometimes in a home studio environment. Connection between the computer and external devices, such as electronic keyboards, is typically made using an Audio Interface. These can be connected to computers via USB, Firewire, and PCI connections, and this guide will consider interfaces using the first of these connection types. USB Audio Interfaces are designed to connect with Digital Audio Workstations and/or PCs, Macs, and other computing devices (for brevity, hereafter referred to simply as PCs, the most common usage). They can be used with microphones and/or electronic instruments – guitars, keyboards and the like - to allow audio to be directed to a recording program on the PC. They can also playback audio from the PC for the purposes of mixing, monitoring, or multitracking as well as receiving or sending MIDI data for the control of electronic keyboards, sound modules, and samplers. With the growth of personal computers came the development of software for music production, and from the 1980s on, there was, in tandem with this, a shift in the style of popular music toward electronic music, generated via sequencers, synthesisers, and other electronic devices such as drum machines. Audio interfaces such as these fit easily into the compact performance and control space of the home-based musician or producer as well as into larger, purpose-built studio spaces.
USB (Universal Serial Bus) is a standardised definition of communication protocols, physical connections, and cables used for connection of computers to other electronic devices. Whilst USB originally evolved in the 1990s to allow standardised connections to keyboards, pointing devices, scanners, and other peripheral devices, the developers of electronic and audio music production devices have come to make use of it to allow connection of these to PCs, and this growth has led to the introduction of the USB audio interface. External USB audio interfaces, which connect to a USB port on a PC, are sometimes referred to as external ‘sound cards’. The use of an external sound card or audio interface, as opposed to the computer’s internal card, allows flexibility with regard to upgrading and also portability. The use of the USB port also allows digitally-encoded audio and MIDI data to be transmitted to and from the PC.
Using a USB Audio Interface
A USB audio interface allows a player or producer to direct audio from microphones or electric instruments into a PC. It also allows playback from the PC so that extra music tracks can be added to the audio already recorded, similar to the tape recording process of ‘multi-tracking’ – building up a musical performance from its constituent parts, without playing them all as a live performance. Some USB audio interfaces also include provision for MIDI (Musical Instrument Digital Interface) signals. This allows players or producers to input data from electronic keyboards or controller devices into music production software on a PC and also allows playback of MIDI data to control external keyboards, sequencers, or sampling devices. The individual player or producer should judge whether or not their requirements extend to include MIDI, or whether their purposes will be best served with an interface working purely with audio signals.
Choosing a USB Audio Interface
The basic process of choosing a USB audio interface is to determine the requirements for the player or producer’s current projects, possibly with some forward planning for future expansion, and to match these with the features offered on the various interfaces on the market. The number of analogue inputs and outputs is likely to be crucial to the producer working with a multi-instrument acoustic ensemble, for instance, but less important to a keyboardist working with MIDI sequencing. Any musician or producer whose work routinely involves a single instrument, such as solo piano, or perhaps a single instrument plus voice, is unlikely to need an interface loaded with 8 or 16 inputs and outputs, whereas someone working with multi-instrument ensembles could be likely to need at least this number, possibly more. Most sellers will usually list the primary inputs in the title or subtitle of their listing, but if in doubt, check with the seller.
Those working with electronic instruments can take one of two approaches – they can work with these instruments externally and send their analogue audio via the interface to a recording program on the PC, or they can direct MIDI data directly from the instrument via the interface to a sequencing program on the PC and, on playback from this, use virtual software synthesisers to generate music from the MIDI data. Obviously, for this style of application, a MIDI-capable interface will be required, and again, the presence of MIDI functionality should be fairly clear from either the listing title or subtitle, but if in doubt, check with the seller.
The most basic interfaces are likely to have two basic outputs to allow monitoring of audio, in stereo, via headphones or speakers. More exotic models could have additional outputs for sending different monitoring mixes to different musicians and/or multiple outputs for surround-sound as opposed to stereo work. Again, the scope of the individual's current and future projects will affect the choice of unit. For connection of other signal processing devices, a basic input/output effects loop can also be useful, and again, moving from the most basic units to the more exotic will yield further flexibility. The individual player or producer should assess what they require from their choice of unit as well as how their choice fits into the overall budget. If there's any doubt about the various inputs and outputs fitted to a particular unit, check with the seller or look for reviews, whether on eBay or on the maker's own website.
In addition to MIDI capability, there are other digital connections that may be required or considered. S/PDIF (Sony/Philips Digital Interface) allows connection of other digital devices for input and output, in two forms – co-axial, with the signal delivered by electric pulses, via physical cable – and optical, where devices are linked with a fibre-optic connection. In both instances, these connections provide for better signal quality than analogue connection. ADAT ports allow the transfer of up to eight audio channels via fibre-optic cable, using a standard designed to interface with ADAT recording machines. Again, the player or producer should consider what, in their current setup, the interface will be required to connect to in terms of their current projects and whether or not further equipment with different requirements will be added later.
Lastly, consider the physical 'form factor' of the unit concerned and how it is intended to fit into the studio or workspace concerned. USB Audio Interfaces can be found in freestanding and rack-mountable configurations, with some freestanding units designed to physically match certain types of computer. Consider the unit's size, either in terms of rack spaces required, or desk/workstation space. This should usually be apparent from pictures within the listing, and listing descriptions will, for rack-mounted units, often state the rack space requirements in terms of standardised height units - 1U equates to one unit, 2U indicates two.
Finding a USB Audio Interface on eBay
From the eBay homepage, select Shop by Category, and expand the category list to Show All Categories. Select Musical Instruments, Pro Audio Equipment, and then Audio/MIDI Interfaces. The individual type can be selected from the LH menu options, showing only USB Audio Interfaces. A number of other selection options are available, allowing search results to be further refined, including selection by input type – those with XLR inputs, for instance, or by manufacturer, such as Tascam.
There is no universal ‘best’ USB audio interface as the player and/or producer requirements will vary by their individual approaches, the equipment they have in use at the time of purchase or which they plan to acquire, and whether or not they work in a solo context or with groups of musicians. The capability of various interfaces varies by manufacturer and intended application, and the individual purchaser should assemble a list of requirements, consider what other equipment the interface will be used with, allow some flexibility for future expansion, and choose the interface that best matches their requirements and budget.