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Sound Connections in Audio Networking

The world of networked AV is its own kind of Babel. CobraNet, developed by Peak Audio in the mid-1990s and the first successful digital audio networking protocol, had a shot at becoming an industry standard. But while its acceptance by the pro audio industry was fast, it wasn't fast enough to outpace a host of other companies. We look at four of today's prominent protocols.

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QSC

Pros: Low latency (0.3 milliseconds), high capacity (up to 512 bidirectional channels per interface), fault tolerance, scalable Layer-3 networking support, Wide Area Network (WAN) streaming option, standard Ethernet network design, and coexistence with other network applications.

Cons: Q-LAN is available only on QSC's Q-Sys products and it supports just one sample rate (48 kHz). The company says multiple sample rates up to 386 kHz will be supported in future releases.

Suitable Applications: Its centralized, high-capacity nature makes Q-Sys networking most suitable for larger installations.

QSC's Q-Sys provides audio routing, processing, control, and monitoring functionality. The primary elements are the Core and the I/O Frames. The Core is the centralized brain of the system and allows any input to be routed to any output without convoluted signal paths. Although Q-Sys uses a centralized structure, it retains the ability to physically locate the input and output connections near their sources and destinations using I/O Frames. Each I/O Frame can house up to four I/O cards enabling up to 16 channels of input and/or output in a single unit.

Q-Sys utilizes Q-LAN, a proprietary, standards-based, low-latency gigabit Ethernet network implementation that's responsible for audio routing between devices and ensures that all signals are transmitted from source to destination in less than 0.3 milliseconds. Q-Sys combines Q-LAN with 32-bit floating point distribution and high-performance A/D and D/A converters resulting in very low latency of less than 2.5 milliseconds from any input to any output with up to seven network switch hops. In addition to low latency distribution, Q-Sys also supports long-haul IP streaming of audio over WANs as well as auto-discovery and configuration of end nodes.

Gross says Q-Sys' Layer-3 support makes the system unique. "Higher layers imply greater interoperability, scalability, robustness and security," he says. "The Internet is built using Layer-3 IP networking. Your office LAN is built using Layer-2 networking."

On the other hand, he says, "There is no 100-Mbps option for Q-LAN. At first blush, this might seem to be a strike against Q-LAN until you realize that gigabit Ethernet uses the same Cat-5 cable you use for Fast [100-Mbps] Ethernet, and commercial-grade gigabit switches are now cost-comparable with 100-Mbps equipment. Even if you don't appreciate the expanded channel capacity of a gigabit connection, you will certainly appreciate the improved latency."

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AT&T Park in San Francisco was among the first large Q-Sys installations.

At AT&T Park in San Francisco, installer ProMedia implemented a Q-Sys system comprising two Q-Sys Core 3000s, 16 I/O Frames, eight mic/line input cards, two line output cards, 56 dataport cards. The company also integrated 102 existing QSC PowerLight and CX amplifiers. Demetrius Palavos, senior sales and design engineer for Promedia, says the company chose Q-Sys in large part because the facility's existing QSC amplifiers could remain in place.
"Using Q-Sys let us simply replace the CM16 amplifier control devices with nodes on the Q-Sys network," he says. "That made it a plug-and-play proposition."

Palavos says performance of the Q-Sys network has met expectations, but emphasizes that the equipment that rides the network plays a significant role in the choice of platform. "If these had been Crown amps, we would,probably have gone with the BSS London [network]," he says. "You're not going to look at just the network by itself."



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