We will have a look at audio interfaces with effects included, audio interfaces with mixing desk or moving sliders included, audio quality considerations, balanced / unbalanced I/O, bits and sample rates, connection to the computer and the manufacturer characteristics. Along with the points discussed in part I of choosing your audio interface, this article will help you make a better buying decision.
Audio interfaces with effects included
Most audio interfaces allow on board mixing where inputs and outputs can be mixed and routed for monitoring purposes. Hardware DSP (digital signal processing) is included in the equipment, for the on board mixing ability.
Added to this, nowadays audio interfaces include specific DSP functions. This includes effects, physical modelling, functions for surround systems etc.
Effects within an interface are useful in two ways:
- processing power needed for the effects is given by the audio interface, thereby saving CPU power of the computer
- using interface effects avoids buffers and delays associated with computer based systems.
Interfaces with built in DSPs can vary from those offering very basic effects, to one desirable high quality effect, to a group of good quality effects especially suited for use on stage.
Latency while monitoring – vocalists
Vocalists and other performers want the monitoring to be without delay. Added to this, being able to listen back to their voice along with appropriate reverb can be useful for the performance.
Signals treated using vst plugins, within your sequencer, will have a few milliseconds delay even with the lowest buffer sizes of modern interfaces. This delay is avoided when we use effects from the audio interface.
Zero latency monitoring
If we can reduce the latency to a couple of milliseconds, humans may not know the difference from ''true zero latency' of analogue connections. This is possible by using 'direct monitoring' where the input A-D converted signal is sent directly to the D-A to the output and to the monitors of the perfomers. A little bit more about latency.
Effects for vocalists and performers
Alesis MultiMix 8 USB 2.0 Mixer is cheaper with lesser number of channels and very similar functionality as the 16 channel one.
The three most useful effects for vocalists and other acoustic performers are:
- compression: to even up the levels
- reverb: to add the necessary comfort for the sound, to make it sound in a good acoustic environment
- EQ: to alter the frequencies and thereby the timbre or quality of the sound, as the performer would like it on her monitors.
For guitarists, basic amp modelling helps them listen to the direct monitoring as if it has been passed through guitar amp/ speaker.
Line 6 Pod and Behringer V-Amp ranges are examples of equipment that have physically modelled preamps with analogue line-level and/or digital outputs that you can connect to an existing audio interface. This allows detailed tone control if you want to record directly to a computer.
Also available are audio interfaces with their own physical modelling built in.
Interfaces with moving sliders
It is convenient to have multi-channel audio and midi interfaces combined with moving faders to adjust the levels and mix. Products like Digidesign's Digi 003 LE and M-Audio's Project Mix I/O are examples.
We get what we pay for, but the budget audio interfaces available now are very good for the price that the difference with expensive models is not very obvious. Below are a few things about factors that affect the audio quality.
Balanced input output
Cheap budget interfaces may have unbalanced outputs while if you spend a bit more, you get good interfaces with balanced outputs. Spending that extra money and getting balanced output will be very useful to avoid problems when recording, especially more than one electronic device.
Why is unbalanced bad?
Connections between unbalanced outputs and inputs are made with 'single-core plus screen' cables that can pick up interference en route (especially with longer cable lengths). Moreover, where such cables connect two or more devices that are already earthed via their mains power supplies, the unbalanced cable between them creates a 'ground loop' that can result in background hums plus digital nasties including buzzes, whines and whistles that vary with mouse, hard drive, and graphic activity.
Balanced I/O uses 'two-core plus screen' that avoids all interference problems. When we use two cores, any interference picked is picked up equally by both the cores. This cancels out the interference at the other end of the cable. Ground loop problems also don't occur with balanced I/O because now, the screen connection is not part of the signal path.
have a wide range of connectivity options.
Background noise levels or distortion are not a problem these days since you can use 24 bit recording instead of 16 bit, even in budget equipment. Modern audio interfaces come with 24 bit recording. So, nothing much to worry about in that respect.
Sample rate seems to be a very personal choice. Though modern interfaces talk about 192kHz recording ability as one of their core features, in practice I haven't met a single musician nor heard or read about one who actually uses 192kHz for their recordings.
Higher the kHz, larger the size of the wave files, more the resources of the computer used. Can we really sense the difference that 192kHz makes? Not very sure.
There are famous producers who still use 44.1kHz for their international productions, especially when the final required product is a Red Book CD Audio.
48kHz is used by many keyboard based musicians and home music makers since they feel it is better than 44.1kHz, at the same time the resources used are within allowable limits of their equipment.
I know a much acclaimed sound engineer and studio builder who uses 88.2kHz sample rate. According to him 88.2kHz is a better choice than 48kHz because 88.2 is a multiple of 44.1 which is the final kHz the signal gets converted to. During the analogue time, this was important to avoid conversion artifacts, though in the digital realm this may not be of much concern.
Orchestral, jazz, folk, acoustic based recordings producers seem to prefer 96kHz.
Mixing desk + Audio Interface
Some products combine the functions of analogue mixing desk and audio interface into a single product: the USB/Firewire mixer.
This allows the hands-on approach of analogue mixing including features like analogue EQ and true zero-latency monitoring, along with the convenience of using a single cable to record multiple audio channels into the computer.
Cheaper models will record through different channels, but offer a stereo out to input into your computer. More expensive models like Yamaha N12 Digital Mixing Studio and Mackie Onyx 1620i 16-channel Premium FireWire Recording Mixer will give you separate output channels for each of the recording channels, so that you can input them separately into the computer and work on them in the computer.
Connecting to the computer – PCI
The Focusrite Saffire 6 USB is a two-in/four-out USB audio interface that uses the award-winning Focusrite mic preamps.
The Focusrite Scarlett 2i2 is a 2 in / 2 out USB recording interface with two award-winning Focusrite preamps. The front panel Neutrik combination input can be used to connect line and instrument level signals as well as microphones. And it’s solid enough to take on the road when you travel
Advantages of the PCI and PCIe connection for desktop users:
- tighter timing on MIDI ports
- lower audio latency than either Firewire 400/800 or USB2 formats
- don't generally require external power supplies.
Break out box + sound card versions offer as much convenience as the Firewire/USB version while most of them don't need an external power supply.
The RF (radio frequency associated with AC power) inside a computer case does not seem to affect the audio quality though the PCI cards are kept within. Conflicts within the computer are not very common these days to affect the performance.
Disadvantages of PCI
- PCIe slots are taking over PCI
- need to open up the computer to connect the card
If you want a compact yet portable interface to partner a laptop, there are a few audio interfaces based around the Cardbus slots found in many laptops,
Connecting to the computer or laptop – USB and firewire
USB and Firewire are the two popular and portable means of connecting the audio interface to a computer or laptop. Since the connection is external, it is easy to move the audio interface between computers and laptops.
USB 1.1 ports had a low bandwidth and were not suitable for audio work, but the Hi-Speed USB (2.0) interfaces available now can manage more simultaneous inputs and outputs than Firewire 400 devices. Firewire 800 options are available and have wider bandwidth than USB 2.0, but most of our needs won't need that kind of bandwidth.
Negative points for USB and Firewire audio interfaces:
- the 'no interface detected' problem. The interface is connected, but faces connection problems.
- some of the USB/firewire audio interfaces use extra
In the case of Firewire interfaces, make sure that the controller chip-set used by the firewire port in your computer is compatible with the particular audio interface. The website of the manufacturer will have relevant information on this, since some chip-sets are not compatible with certain audio interfaces.
There is another connection format specific to be used with Protools and related hardware. M Audio and Protools belong to the same company: Avid Technology
Choosing the manufacturer comes into picture because each of them have their own characteristic strong points. For example:
- Focusrite interfaces are known for their excellent mic preamps
- TC Electronic interfaces have good DSP reverbs and are low in jitter
- M-Audio are among the most affordable while being good for a wide range of applications
- RME and MOTU are reliable and sturdy in make
- Lynx make quality PCI soundcards, though nowadays use of PCI is getting lesser.
Understand your recording needs, go through the factors listed here and in part 1, find something within your budget, start recording and producing your music.