Bidirectional AES/EBU Digital Audio and Remote Power over a Single Cable

TitleBidirectional AES/EBU Digital Audio and Remote Power over a Single Cable
Publication TypeConference Paper
Year of Publication1999
AuthorsFreed, Adrian
Conference NameAudio Engineering Society 107th Convention
PublisherAudio Engineering Society
Conference LocationNew York, NY
Abstract Although the AES/EBU digital audio standard has already been adapted to optical, twisted pair [1] and coaxial cables [2]. This paper explores cabling options for new and emerging applications of digital audio communications. Enabling features include remotely powering devices over the audio cable and bi-directional communications. Remote power benefits both ends of the audio reproduction chain: microphones and instrument pickups on the input end and loudspeakers and headphones on the output end. Bi-directionality is an important feature because so many audio applications have inputs and outputs that are physically proximate, e.g., headset microphones with monitoring, stage boxes, and signal processing effects. In contrast to studio situations, the aforementioned "live" audio applications require processing elements to be physically dispersed in locations where it may be expensive or inconvenient to provide electrical power. Note that although a guitar, for example, is primarily a source of audio, the guitarist can certainly take advantage of audio sent down a single cable to provide a monitor audio feed, or a tuning reference. Providing headset monitoring is now widely accepted practice for singers in live performance application, favoring a bi-directional audio link. There are also opportunities in digital audio applications to exploit bi-directional communication of gestures and indicator values [3]. The remote power requirement precludes optical and wireless approaches, leaving twisted pair and coaxial as the main alternatives. The computer industry has recently focussed on twisted pair solutions with USB [4] and Firewire [5]. GMICS [6], an interesting new proposal from Gibson Guitar, adopts 100BaseT Catagory 5 cable as one possible physical layer implementation for a multi-channel protocol supporting powered, bi-directional communication. This paper communicates results of exploratory experiments with other physical layer options: coaxial and tri-axial cable.