Electronic Design

PoE And The Garage Band

Not every PoE application is an enterprise telephone or RFID reader. Power over Ethernet is a component of one of the more unusual new applications of Ethernet technology. In 1999, Gibson Guitars of Nashville, Tenn., introduced an Ethernet-based power-over-LAN (local-area network) concept called MaGIC (for Media-accelerated Global Information Carrier), which now complies with IEEE 802.3af. In 2002, Gibson introduced the Digital Guitar, a Les Paul-model lookalike with an RJ45 Ethernet-cable jack (see the figure).

Gibson's 87-page MaGIC specification (www.gibsonmagic.com/magic3_0c.pdf) says, "MaGIC \[provides\] up to 32 channels of 32-bit bidirectional high-fidelity media with sample rates up to 192 kHz. Data and control can be transported up to 30,000 times faster than MIDI. Added cable features include power for instruments, automatic clocking, and network synchronization." The company chose Ethernet in lieu of AES/EBU, S/PDIF, LightPipe, and FireWire because "none satisfy the unique requirements of live performances, particularly in the areas of clocking, distance synchronization, and jitter/latency management."

Development was supported by the University of California at the Berkeley Center for New Music and Audio Technologies, Xilinx, and 3Com, among others. Goals included reliability over long distances, local repair, simple installation and ease of use, the ability to support multiple channels of advanced fidelity audio and video, scalability, support for intuitive control interfaces, and the ability to provide power for digital instruments without batteries.

The Digital Guitar converts the analog signal from the pickups into a digital signal inside the guitar. Stray frequencies entering the guitar pickups are completely eliminated, along with analog line noise induced through the guitar cable. It provides signal processing on a string-by-string basis, which makes it possible to adjust volume, pan, and equalization of each string individually. Gibson says that the guitarist can have a crunch (heavy metal) sound on the low strings, medium distortion on the middle strings, and a clean sound on the high strings.

Choosing the Les Paul for this treatment reflects more than the coincidence of 2002 being the 50th anniversary of the model. In the 1950s, Paul was a technical innovator who, with wife Mary Ford, pioneered multitrack overdubbing in what was essentially their home studio. The significance is that the music business is undergoing a transformation today, with peer-to-peer networks undermining the traditional record labels and bringing together artists and listeners in a more direct relationship. Like Les Paul, today's musicians and vocalists are apt to use home studios or small commercial facilities operating on a shoestring budget. MaGIC, or an industry-wide standard that evolves from it, may do for production what peer-to-peer networking has done for distribution.

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