USB and Ethernet
Some companies have proposed using other interconnects in professional audio systems. The options are USB and Ethernet.
Some of the low-end consumer-centric music I/O boxes utilize USB 2.0. But USB has a number of limitations in professional applications. USB 2.0 has a theoretical maximum transfer rate of 480 Mbps. Realistically, USB doesn't come close to that rate even in a simple scenario with a PC linked directly to a single peripheral.
But the media-access scheme and protocol are even bigger roadblocks when it comes to professional audio. USB requires that the host PC control all operations. Were an audio application to move data from an I/O box to a mixer using USB, the host would have to read the data from the I/O box and send it to the mixer.
USB lacks any isochronous or synchronization capabilities. In a music application, the bandwidth wouldn't support multiple I/O boxes or mixers. And even if it could, you couldn't synchronize the recording back in the studio.
What about USB 3.0? Certainly the emerging new flavor is supposed to offer much higher data rates. But not cheaply - there are very expensive modular host interfaces on the market.
It's not even clear at this point that USB 3.0 will follow USB 2.0 into ubiquitous deployment. Handset makers are balking at supporting USB 3.0 because of the inconvenience of the connector.
Also, standard Ethernet is also incapable of serving the professional audio application - even the 1-Gbps flavor. Ethernet lacks the required isochronous ability. The Ethernet community is attempting to address the shortcomings of the network technology in multimedia applications by adding the Ethernet AVB (Audio/Video Bridging) layer. We've yet to see that technology mature. But in any event it will still lack the topological advantages of 1394. Moreover, it will be a significant added expense to support Ethernet in I/O boxes and mixers.
Integrating 1394 in audio products
Design teams working on professional audio products have a number of options in terms of ICs that support 1394. There are numerous general-purpose 1394 ICs on the market. And there are some ICs that specifically target professional audio.
TC Applied Technologies, for example, offers the Dice family of ICs. The Dice Jr product can support as many as 64 channels of audio sampled at 96 kHz. The IC includes a direct interface for A/D and D/A converters and includes a hardware mixer.
Extending 1394 in professional audio
There are compelling reasons that could lead to broader integration of 1394 technology into professional audio products. For example, it might make sense to integrate 1394 interfaces directly into instruments and even microphones. To ensure synchronization capabilities, such a microphone would need to be a slave to another product such as a mixer or I/O box. And the microphone would require an integrated jitter-free clock to support synchronization.
It also makes sense to integrate 1394 into several types of speakers. For example, studio-monitor speakers would be a natural for the interface. This kind of implementation allows music to remain in the digital domain from the initial data conversion right through to the analog conversion that drives the speaker.
Not only are professionals using 1394. Now, the trend among pro-am and amateur musicians is toward the FireWire interface, proven and effective across a wide range of platforms.
About the author:
Morten Lave, a veteran of the IC and music industries, is chief executive of TC Applied Technologies, a division of TC Electronics. He can be reached at MortenL@TCTechnologies.tc.