Live Sound

Networked Amplifiers

VERSATILITY, FLEXIBILITY FOR TOURS AND INSTALLATIONS 7/01/2008 8:00 AM Eastern

In its most basic form, an amplifier network comprises a power amp with a computer interface, a system controller (generally a PC) and connecting cables. Network-to-amplifier interfaces come in various flavors. Some amps connect directly to a PC via a built-in interface or a network card inserted into a rear panel expansion slot. Other designs employ a “bridge”: a device that connects between the amp(s) and PC, and manages communication between the two. Most manufacturers use standard Ethernet hardware (i.e., Cat-5 connectors and cable) for their networks to ensure a familiar, cost-effective, off-the-shelf interface. Often, the network can be connected to a wireless hub so a physical link to the computer is unnecessary. With your amps and laptop on a wireless network, you can walk the room while listening to the P.A. and tweak output levels or EQ settings.

Amp networking falls into three categories — monitoring, control and audio routing/distribution — so check out what functions an amp is capable of before you buy into a manufacturer's network. Monitoring via network allows you to watch what an amp is doing in real time, usually via PC. The amp sends status data to the PC with parameters such as internal temperature, AC mains voltage, input/output levels, clipping, load monitoring, output voltage/current and status of protection circuitry. (Most manufacturers provide amp-networking software free of charge). Load monitoring is of particular interest as an engineer can spot shorts or open circuits in loudspeakers before they become a problem. Some programs store a time-stamped fault log as a text file so failures can be identified even when the engineer is not present.

Lab.gruppen PLM1000Q

COMMAND AND CONTROL

Network systems with the ability to monitor an amp can also usually remotely control the amp. Remotely adjusting the amp gain is a huge convenience, especially in multi-amp systems where you can tweak levels of LF/MF/HF amps without running back and forth to the amp rack. Once limited solely to I/O level changes, modern network control facilitates muting, gain, multiband EQ, channel delay and crossover functions. Another plus is a security lockout feature that prevents unauthorized users from changing DSP parameters.

A recent trend shows DSP (traditionally from an outboard processor) starting to move directly inside the amp. Taking this concept further, Lab.gruppen's PLM10000Q amp merges Dolby Lake processing, Lake Contour and Mesa Parametric EQ with network monitoring, control and audio distribution.

Amplifier networks that support monitoring and control don't necessarily support audio networking, the ability to route and distribute audio over the network. Amps having only traditional analog inputs differ from those that carry the actual audio signal on the network. These amps may accept audio via analog input or AES/EBU digital input, as well as via the network connector. As with control and monitoring networks, most audio networking is accomplished using Cat-5 hardware. Some manufacturers have developed their own proprietary audio network protocol (i.e., Harman's HiQnet), while other networks such as CobraNet or EtherSound are supported by a number of manufacturers. Some of the amplifiers listed in this roundup are compatible with the latter two protocols, typically with the addition of an expansion card — but be aware that some amps may not be able to play in the CobraNet or EtherSound sandboxes.

Network-able amplifiers have other useful features. In systems without audio networking, an amplifier having audio thru connectors can simplify expanding your system without the need to add audio splitters or distribution devices. When you need to add more amps to the system, simply connect the amps' thru connector(s) to the next power amplifier in the chain. This is great for situations in which you might need to add an amp and a few subwoofers to a mobile P.A. system for a specific venue or performance. On networks that support audio distribution and routing, thru connectors may not be necessary, as audio is carried through the network anyway and the software typically provides a means for splitting an audio signal. Keep in mind that there could be a critical situation in which you may want to input both analog audio and digital audio via a network as a form of redundancy.

Today, networked amplifier control is mostly a necessity in pro touring and fixed installs. Fortunately, there are ample product choices. The chart on the following pages shows a sampling of what's offered.


Steve La Cerra is Mix's sound reinforcement editor.


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