The Source

Our tech support guru Chas offers his top ten tips for choosing an audio interface. While Chas has used some of Source’s favourite products as examples - such as PreSonus & Lynx - the same principles apply whatever brand you end up choosing. Happy shopping!

1. Type of interface

The first thing to consider is how your new audio interface will connect to your computer, and that depends on what connections you have available - for instance USB, FireWire or PCI.

Each connection method has its pros and cons but generally speaking they’re all capable of similarly high performance figures. There are various things to look out for here - for instance Firewire devices often don’t like sharing the Firewire bus with anything else, so if you already use a Firewire drive for backup or recording purposes it might be worth using a audio interface that connects in another way. If you are considering a PCI or PCIe card but you already have a lot of other similar cards such as Universal Audio UAD1 or UAD2 DSP cards in your system then simply finding an available slot can be problematic.

If you’re on a laptop then ExpressCard or USB are generally your only options, though again if you’re planning to use a UAD2 Solo Laptop card in your machine’s ExpressCard slot then a USB audio interface would be an ideal combination.

Using this criterion as an initial means of eliminating unsuitable products you should be able to narrow things down to a manageable shortlist with which to proceed…

2. Compatibility with your existing system

Once you’ve narrowed the choice down by considering which type of connection suits, you should also check with the websites of those manufacturers that you’re considering as to special requirements for their kit. For example, some Firewire devices require Firewire 400 connections, and often work less efficiently on either Firewire 800 or 400/800 combi sockets, and some devices greatly favour certain Firewire chipsets rather than those by other manufacturers - so it’s worth checking these specs in advance.

Most manufacturers have ample information on their site about these issues, and similarly where PCI or PCIe cards are under consideration there may occasionally be issues with particular PC motherboards or chipsets which you should check before purchase.

3. Form factor

Interfaces come in a variety of formats, including 19” rackmount boxes, standalone table-top units, or in-line USB dongles. Which you choose will depend partly on your studio layout, how you want to work and the number of inputs and outputs you require.

You’ll generally find that manufacturers produce a range of units derived from the same core technology, but in different physical formats according to the range of features and number of inputs/outputs provided. For instance the PreSonus FireStudio range spans from a standalone 6x10 model (the FireStudio Mobile) via the rack mounting 10x10 FireStudio Project right through to the top of the range FireStudio 2626, which offers 26x26 inputs/outputs.

As a further consideration some people find that the combination and style of knobs, buttons and software menus has a considerable effect on their workflow and creativity, so it’s worth taking some time to check how you access frequently used functions and whether things you want to change can be done via hardware, software or both.

4. Number of inputs & outputs

The number of input and output options you look for should reflect your usual recording practices: if you mic up a live band on a regular basis you might use anything from 3 to 8 mics for the drum kit alone, plus other instruments on top of that. In this case a pair of synchronised 10 input units is a bare minimum; if you record every instrument and vocal yourself by laying down one track at a time then a 2 in / 2 out unit will easily suffice, thereby saving you space and money.

Looking at outputs, if you mix to 5.1 you’ll need at least 8 discrete outs (to include simultaneous stereo fold-down) whereas if you work exclusively in stereo then 2 outputs plus a headphone output should be fine.

Some manufacturers make several different versions of the same card with different configurations of inputs and outputs, for example the Lynx Two PCI audio interface can be purchased in three versions - the Two-A (4 ins and 4 outs), the Two-B (2 ins and 6 outs) and the Two-C (6 ins and 2 outs), so if you particularly like the look of a card from its specs and interface but feel it has the wrong combination of in/out options you may still be able to obtain a version that will work for you.

5. Proportions of input types

Similarly to the above point, a look at which types of inputs your shortlisted interfaces feature will save frustration in the long run: if you never play or record guitar or any similar instrument then high-Z instrument inputs are superfluous; likewise if you work exclusively with samples and pre-recorded material you can dispense with mic inputs, whereas if you are always dealing with live vocals and instruments then multiple mic inputs will be your guiding statistic. You should also check which of the mics you commonly use require phantom power and whether this will be provided for; some may be able to work from battery instead (the Rode M3 or NT3 models for example are equally happy on either phantom or battery power) and others may derive phantom power from their own proprietary power supplies (valve mics such as the Rode K2, NTK or Classic II are examples of this type).

Tube (valve) channels can also add a valuable option in this digital age, whereby a signal can be ‘warmed up’ with a classic analogue sound before or after being recorded digitally: if you feel that there is no real software substitute for this, then a tube channel option is a must, and units such as the PreSonus FireStudio Tube allow seamless integration of this with your DAW. Phono inputs (inputs that can take the output directly from a vinyl deck with the corrective equalisation this requires) are also a great option if you DJ from vinyl or plan on digitising a vinyl collection.

6. Digital features

Another area that relates to what you want to do with the interface now or in the future is what digital options it provides: if you plan to connect to other digital kit, take a look at what type of physical connections are provided - the SPDIF (consumer type) digital signal can be sent via coaxial connections (which look like traditional RCA phono plugs, but with only one socket for input and one for output, since each socket carries a stereo signal) or optical connections (which carry the same signal but using a fibre-optic lightpipe connection).

The AES/EBU connection is a more professional digital format and is generally not interchangeable with SPDIF. MADI and ADAT are digital multitrack formats - if you don’t have any other equipment that uses these then there’s no point in paying extra for them; many manufacturers cut out such options to make lower-priced version of the same unit available, as for example in the various members of the PreSonus FireStudio family (FireStudio 2626, FireStudio Project, FireStudio Lightpipe, FireStudio Tube, FireStudio Mobile), each of which features a greater or lesser number of input and output options from which to choose.

If you plan to have a wider range of digital kit running in your set-up you also need to be aware of digital clocking issues: all digital units use the clock signal embedded in digital audio to make sure they stay perfectly synchronised with each other, and every digital system must have only one master clock source with all the other units following (‘slaving’ to) that one source. The quality of the master clock source (and in particular its immunity to ‘jitter’ - momentary fluctuations or irregularities in the clock signal) can have a profound effect on the perceived quality of the audio. The FireStudio family employs a technology known as JetPLL specifically to reduce jitter - thus improving stereo separation and producing clearer, more transparent audio.

If you have a requirement for super high-quality analogue-to-digital and digital-to-analogue conversion there are several manufacturers who cater to the high-end market, and a unit such as the Lynx Aurora (available in 8 and 16 channel versions with PCI, PCIe, Firewire, ADAT, MADI and Pro Tools interface options) will provide a quality and transparency that’s pretty much unbeatable, as well as every conceivable clocking and synchronising option. The digital clocking available from high-end units like any of the Lynx products is ideal for use as a system master clock - but almost any professional audio interfaces clock should be far superior to the digital clock from a computer as these were never designed with high quality digital audio in mind.

7. Performance specs

How fussy you are about the performance specifications is a very individual thing: some people pay great attention to a noise floor a few decibels lower than a competing unit, others maintain that with the 144-odd dB of dynamic range available with 24 bit recording there’s no longer any need to worry, and these days any professional audio interface should be well within acceptable limits for all but the most demanding high-end applications.

Likewise figures such as THD (Total Harmonic Distortion - how accurately the input to a audio interface is reproduced at the output) and Frequency Response (the range of frequencies that the unit will transmit reliably) for any pro or semi-pro audio interface these days are usually way better than most users would need.

Checking that the maximum supported sample rates are what you need is important though: if you regularly record at 96kHz and plan to go to 192kHz you’ll find that not all audio interfaces support this; if you never go above 44.1kHz then this won’t be such an issue.

8. Reliability & local repair facilities

It may seem obvious, but have a look at online forums and similar places to get an idea of how reliable your shortlisted interfaces are considered to be by end-users! With audio interfaces - as with anything else - you get what you pay for, and a £900 card will usually perform better and work solidly for longer than a £90 card, but the level of use it’s subjected to is a big factor: one of the things that distinguishes professional from consumer audio interfaces is that pro audio interfaces are designed and built to be able to cope with a very high level of use without complaint - 12 hours a day, 7 days a week for years at a time in some cases -whereas consumer cards (which might work perfectly for many years if used for a few hours at the weekend and during holidays) might start to show signs of strain quite quickly if subjected to such high pressures. Be realistic about your needs here: there’s no point buying a tank if an SUV will fit the bill, and money saved on your audio interface could usefully be put towards a better vocal mic or compressor…

The availability of local repair facilities will hopefully never concern you - but if you should need to get your audio interface repaired or serviced then being able to do so easily and quickly within your country can be no small advantage and the difficulties and extra costs of having to deal overseas can sometimes be considerable: money you save on a cheap ‘grey import’ purchase through the likes of eBay can quickly be lost this way.

9. Driver availability & stability for your OS

Nowadays this is not usually an issue, but you may sometimes find that a manufacturer has not yet made drivers available for the computer operating system you are using (or plan to upgrade to shortly), or that a brand new audio interface model does not have drivers written for a legacy OS you want to stick with: either problem can be a deal-breaker. We frequently try to help people who want to run slightly older cards on Windows 7 or Snow Leopard and we also hear from people wedded to XP or Linux…

10. Bundled software, accessories & extras

Last but not least, value for money - what do the manufacturers of the interfaces you’re considering throw in to sweeten the deal? Many companies bundle Digital Audio Workstation (DAW) software with their units which allows you to get up and running with a working recording system straight out of the box with no need for further purchases - PreSonus for example include their own Studio One Artist DAW package with all their audio interfaces: a quick trip to the shops in the morning and by tea-time you could be well on the way to your first Grammy!

You should also check that any specialist breakout cables, adaptors etc are included with the unit - they may be perfectly easily obtainable elsewhere, but the extra cost may wipe out perceived savings.