Firewire Audio Interfaces Guide

The Quick Start Guide to

FireWire Audio Interfaces

Provided by your friends at The Home Recording Studio Guide A Division of New Art Today

What’s an audio interface? This is the hardware (a separate unit or box) that allows sound to be input and output from your computer. It might be built-in to your computer or you may have paid extra for a "sound card". If you want to spend a bigger chunk of money you can buy a unit that has different sorts of 'plug-in' types like the 'RCA' connectors or 1/4 in. 'phono' plugs or even what's called XLR connectors. Or simply it is much like a mixer that will combine analog inputs and preamps. However, after the preamp, the signal is converted to digital information and sent via digital output to a computer. The digital information is processed via software and then returned to the interface where it is converted back to an analog signal for playback. In simplest terms, an audio interface connects your microphones and other sound sources to your computer - it bridges the gap from analog to digital. Audio interfaces are commonly equipped with mic preamps, line inputs, and a variety of other input options. It is briefly a piece of hardware that acts as an intermediary between the analog world of your mics and instruments and the digital world of your computer. Computers can be pretty smart, but when it comes to sound, they need a translator that can convert sound waves into the digital language of ones and zeroes. Audio interfaces provide this translation. You might be asking yourself, "If audio interfaces are often equipped with preamps, why wouldn't I just buy a channel strip or preamp?" Well, the answer to that question lies in the analog-to-digital conversion. Traditional preamps and channel strips send out an analog signal, and for audio to be usable by a computer, it needs to be digital. The audio interface converts the analog signal from its inputs to a digital output, making it easily digestible for a computer.

Benefits of choosing an audio interface over a soundcard: With a brief background on the internals of a soundcard, you will agree that although most of the consumer’s soundcards that come built-in with your computer can be used for audio playback and recording, these soundcards are not meant to be used for music production. The onboard soundcard is OK for games and MP3s but when it comes to recording audio and transferring to digital then having an Audio Interface is an absolute must, as the quality of the sound produced is based on this important piece of hardware. A sound card is a hardware that lets you record and playback audio. It sits inside the computer in a PCI slot and you connect all the cables at the back of this card. Audio interfaces, on the other hand has a box that sits outside the PC and a cable that is connected to the PC, either to the PCI card or to the USB/Firewire slot depending on the type of the interface. The breakout box contains slots for all the input and output audio/midi connections.

Some of the limitations of a consumer sound card include: • High latency (delay in the reproduction of sound, between initiating a sound and hearing it) • General sound quality is not great • Low sampling rates (recording quality is poor) • The drivers may not work with most of the audio recording software applications • No MIDI port. You cannot connect external keyboards/synths • It is intended for home and office entertainment use. The emphasis is more on playback and casual use Audio Interfaces, on the other hand, do not have the limitations listed above making them suitable for serious audio work. Some of the features on a professional soundcard include: • Low latency sound recording and playback • Usually follows the ASIO protocol (suited for sound engineering and music software) • Comes as external rack-mountable units which can be connected using USB 2.0/Firewire • Large number of input and output connectors • Hardware support for multiple input and output sound channels • Higher sampling rates compared to a consumer soundcard • Multi-channel data recording and real-time audio mixer and processor Finally we can say that an audio interface is a professional sound card.

What it looks like?

Audio Interface Main Components: •

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Sound Card: This card, also called a PCI card because it fits in the Peripheral Component Interface (PCI) slot in your computer, allows your computer to read and understand the digital information coming from and going to the converters. Without a sound card, your computer doesn’t know what to do with the musical data that it receives. Analog-to-digital(AD) and digital-to-analog(DA) converters: These converters allow you to get the sound from your instrument, direct box, or preamp to the sound card (the AD converter’s job) and from your computer back out to your monitors (the DA converter’s job) Direct Box: A direct box (technically called a Direct Induction Box or DI box for short) lets you plug your guitar directly into your recording device without having to go through your amp first. Microphone preamp: This is a requirement if you want to plug your mic into your recording device. The preamp amplifies the signal coming from your mic so that it can be recorded. Drivers: Drivers are the software components that allow audio computer programs to talk to your soundcard; they come along with the card. The driver is the critical code that manages the traffic of data going from the cpu to and from the DAC. It organizes the data so the CPU can fetch it when the audio application says it is needed.

Connectivity: There are three main types of audio interface formats: PCI card. This plugs into a PCI slot on your computer's motherboard. It may place all its connectors on the backplate, a second backplate that installs next to the board but doesn't take up a slot, or have a cable that goes to a separate (usually rack-mountable) breakout box that's festooned with connectors. •

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Advantages: Cards usually offer the tightest integration with the computer and the best MIDI timing. Also, if there's a breakout box, the connectors can be placed where it's most convenient for your studio setup. Disadvantages: You need to open up your computer, and although Windows machines have become quite good about "plug and play," there is still the possibility for conflicts with other cards -- particularly PCI video cards. (If you do use a PCI interface, if at all possible use an AGP rather than PCI graphics card.) Although any conflicts can almost always be resolved, those who aren't into computers may find the experience frustrating.

USB. This type of interface is a separate box that plugs into a computer's USB port. Early USB interfaces got a bad rap because of problems in computer operating systems; however, starting with Windows 98SE and MacOS 9.1, USB functionality was decent and now with Windows XP and Mac OS X, USB is fully integrated into the operating system. •

Advantages: You don't have to open up your computer, and the experience is pretty much "plug and play." It's also easy to move among different computers, even if they're different platforms -- use a USB interface with your desktop, then if you go on the road, plug it into your laptop.

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Disadvantages: USB 1.1 is a relatively slow protocol, so there's a bandwidth limit -- you're not going to get 16 channels of 24 bit audio. In fact, it's more likely you'll get four simultaneous channels... but that will be enough for many applications. Note that although there may be timing issues with MIDI, the latest generation of USB MIDI interfaces with time-stamping can overcome any inaccuracies. USB 2.0 delivers considerably faster performance, but as of this writing choices remain limited.

FireWire. This is similar conceptually to a USB interface as it plugs into a built-in computer port, but runs at a much faster speed than USB 1.1 interfaces. •

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Advantages: Similar to USB, although FireWire interfaces need their own drivers, whereas USB interfaces can often use existing system USB drivers. FireWire was adopted by Apple early on, so many Mac owners gravitate toward FireWire. Disadvantages: As FireWire ports have been built in to the Mac for some time, using a FireWire interface is pretty much plug-and-play. However, many Windows machines will need a FireWire card. Although adding one is a pretty straightforward process, it negates the advantage of not having to open up your computer and install a card.

FireWire Advantages: FireWire provides many advantages over other peripheral interconnection technologies. The cables are as simple to connect as a telephone cord--there is no need for screws or latches. And, unlike SCSI technology, FireWire is autoconfiguring--so it eliminates SCSI device ID conflicts and the need for terminators. FireWire is also a hot plug-and-play technology, which means that a device can be disconnected and then reconnected without the need to restart the computer. FireWire is fast--it can transfer digital data at 200 megabits per second, with a planned increase to 400 megabits per second and beyond. And, the FireWire technology supports expansion--up to 63 devices can be attached on the same FireWire bus. Finally, FireWire includes support for isochronous data transfer, which provides guaranteed bandwidth for real-time video and audio streams.
Real-time data transfer for multimedia applications 100, 200, & 400Mbits/s data rates today; 800 Mbits/s and multi-Gbits/s upgrade path
Live connection/disconnection without data loss or interruption
Automatic configuration supporting "plug and play"
Free form network tool allowing mixing branches and daisy-chains
No separate line terminators required
Guaranteed bandwidth assignments for real-time applications
Common connectors for different devices and applications

Firewire Audio Interfaces classification: Category 1: Low Budget / Beginner Level ($125 to $350): least expensive semi-pro audio interfaces for computers. If you are planning to record using professional microphones, you will need to add a suitable microphone preamp or a good quality mixing board. I usually recommend the mixing board option because it will give you more flexibility in routing inputs and outputs and patching in effects boxes. Examples: •

M-Audio Audiophile FireWire - This is a 4-in 6-out audio interface consisting of a small audio I/O box that connects via FireWire to the host computer (much higher performance than USB!). Analog inputs are line level – add your own mixer or mic preamps. Features 24bit, 96kHz sampling rate capability, with S/PDIF or MIDI I/O. Drivers support: Windows 98SE/Me/2000/XP, ASIO 2, Direct Sound, EASI, multi-card, Gigasampler, Mac Sound Manager, Mac ASIO – and even Mac OS-X!. $350 list price (US).

Category 2: Low-End Pro Level ($350 to $800) While some of these more professional interfaces will have built in mic preamps with +48V phantom power and XLR inputs, others have line-level inputs only. Those products which come equipped with XLR microphone inputs with phantom power are designed to function as close to a complete 'studio in a box' as possible. These products usually include a mixer interface built into their driver software so that the computer takes the place of the mixing board in your studio. Others integrate so tightly with your music software of choice that they accomplish pretty much the same thing. Examples: •

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Digidesign Digi 002 Rack- Here's Digidesign's entry into the 'low end' studio market (~$800). This is a FireWire-based 24-bit audio interface with 8 line level analog inputs and outputs, 4 balanced microphone inputs with phantom power, headphone output, one MIDI IN and two MIDI OUT, coaxial S/PDIF, and also includes the Pro Tools LE software. The Digi 002 system is basically a 'native' version of Pro Tools, meaning it uses the computer's CPU for DSP and mixing instead of the hardware DSP included with a full-blown Pro Tools rig. That means no TDM plugins, but you can use Digidesign's Real-Time Audio System (RTAS) plugins. Supported in Mac OS-X and Windows XP Home Edition. Windows 2000 is not supported, but the Mac-heads out there will tell you that it works much better on a Mac! M-Audio FireWire 410 - This is an analog I/O box (24-bit, 96kHz capable) with 2 mic inputs, 2 line inputs, 8 line outputs, S/PDIF I/O and 1x1 MIDI I/O, that connects to the host computer through FireWire. Driver support for: Windows 98SE/Me/2000/XP, ASIO 2, Direct Sound, EASI, multi-card support, GSIF, Mac Sound Manager and Mac ASIO (including OS X). List price is $500, sells for about $350 (US).

Category 3: Professional Level: These products are designed for use in professional studios. The computer-based products are designed to be expandable with external interfaces and additional DSP, and to connect to the other digital audio devices that are normally found in a full-blown recording studio. The stand-alone products are designed to be used as a full-function, portable "studio in a

box." Example: •

Mark of the Unicorn 896 - The 896 is the latest multichannel audio interface to use FireWire (IEEE-1394) to connect to Mac G4, iMac/iBook and PC laptops equipped with FireWire ports. Housed in a two rack-space chassis, the 896 provides 8 channels of 24-bit 96kHz balanced analog ins and outs, 8 balanced mic preamps on XLR connectors (w/ individually switchable 48VDC phantom power for each mic pre), 8 channels of ADAT Lightpipe I/O, optical or coaxial S/PDIF, AES-EBU and 9-pin ADAT sync connectors. Since it uses the FireWire interface, this should be a really good solution for creating a portable, multichannel DAW based on a laptop computer (such as the Mac iBook or Titanium G4, or Sony Vaio), List price is $1295 (US).

Criteria to choose a firewire audio interface: • • • • • •

How Much Can You Spend? Are You Sacrificing Sound Quality? Which Operating System Do You Use? How Will You Connect It to Your Computer? What Number of Inputs and Outputs Do You Need? Resolution, sampling rate, and bit depth needed

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Do You Want Extra Knobs and Features?

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Do You Intend to Use Pro Tools?

Most common firewire audio interfaces specs and terms: ADAT refers to an 8 channel digital input and output. It is useful for connecting more mic preamps, a second audio interface or computer, a digital mixer, or can be used to add more analog i/o through an 8 channel ad/da converter. When you see ADAT x2 in the chart that means the device has two ADAT ports in and out or 16 channels in and out. (Sometimes two ADAT ports may be used for eight channels at a high sample rate like 96kHz) ASIO (Audio Stream Input Output): This driver format, introduced by Steinberg in their popular Cubase application, runs at a lower level (as it bypasses much of the Windows OS) and therefore typically manages lower latencies than both MME and DirectSound. Many musicians have managed to run their music software with latencies as low as 2ms using ASIO, although 6ms is a more realistic figure, and even 12ms is acceptable in most cases. Emagic’s EASI (Enhanced Audio Streaming Interface) format is derived from ASIO and is capable of slightly better performance with Logic Audio. However, few soundcards now support this option. There are 2 versions. ASIO 1.0 and 2.0. 2.0 adds the ability to monitor several audio inputs at once. Beware that there are drivers that call themselves ASIO drivers that are not. Most notorious are “asio multimedia” drivers. Don’t use that

one for music programs. Look in the driver list for a different ASIO driver that has the name of the interface in it. That is the true ASIO driver. Bit depth describes the number of bits of information recorded for each sample Sampling rate, sample rate, or sampling frequency: defines the number of samples per second (or per other unit) taken from a continuous signal to make a discrete signal Latency - Latency describes the amount of time it takes the input signal to pass through the system, and reach the output. MIDI i/o refers to the number of 16 channel ports there are on the interface. 1/2 means it has one MIDI input and two MIDI outputs. MIDI inputs and outputs are used to connect a MIDI synthesizer, keyboard controller, drum pad controller, and some control surfaces. You need one port for every device you want to connect to the computer. You can always add more via separate MIDI interfaces. Core Audio: This is the main Mac OS X method of handling audio, developed by Apple. There is no Core Audio for windows. Mac OS9 used other methods including ASIO that are no longer supported in OS X. GSIF (GigaSampler InterFace): Designed specifically for just one application — Tascam’s popular GigaStudio software sampler — GSIF drivers also work at a low level within Windows, providing guaranteed low latency of between 6ms and 9ms. If, like plenty of other musicians, you’re interested in GigaStudio and its extensive collection of professional sample libraries, your soundcard must have GSIF drivers; you won’t be able to run GigaStudio without them. Preamps refers to the number of microphone preamps the interface has. Usually these can double as instrument inputs (guitar, bass, etc.) But check on that before you buy. Also some interfaces (but not all) will have insert jacks or send outputs for connecting compressors and other processors. You might want to check on that too when evaluating an audio interface. S/PDIF (Sony/Philips Digital Interconnect Format) i/o is a stereo digital pathway, and may be either coaxial or optical. S/PDIF is useful for connecting digital audio devices, like external a/d converters, effects processors, CDR recorders, even some preamps and keyboards that have digital outs. WDM stands for Windows Driver Model with Kernal Streaming. This is a lower latency driver that allows the application direct access to the “kernal” without going through the Windows OS. This results in latency figure that is fast like ASIO. It was introduced in Cakewalk’s Sonar. So if you want to run Sonar, a card with a good WDM driver helps. However, today cakewalk does support asio drivers. Word Clock refers the presence of a BNC connector through which word sync signals can be sent to other digital devices. It is important that all digital devices connected through s/pdif or ADAT share the same word sync. For simple setups that may have two digital devices, having a word clock connector is not usually necessary. Sync can be sent along through the s/pdif or ADAT connection. It becomes important in rigs where there may be multiple digital devices where it is impossible to send

word sync to all devices.

Best Manufacturers and Conclusion Some of the major and popular manufacturers/brands of professional firewire audio interfaces include M-Audio, RME, Tascam, MOTU, PreSonus, Digidesign, Onyx, etc. Conclusion Choosing an audio interface doesn't have to be rocket science... • Choose a manufacturer with a reputation in pro audio. • Decide how many analog inputs and outputs you want. • Decide how many digital inputs and outputs you want. • Decide whether 24/96 is good enough (it's more than good enough for most people), or whether you

really must have 24/192 capability.

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