Alesis EC-1 A ES/EBU Overview Of Main Functions, Front Panel Setup, About Aes/Ebu Digital Audio

Appendix E, EC-1 AES/EBU Interface

OVERVIEW OF MAIN FUNCTIONS

ABOUT AES/EBU DIGITAL AUDIO

The AES/EBU protocol is the most common professional standard for transmitting digital audio. It is a two-channel protocol designed for stereo pairs, so transmitting from the eight-channel ADAT M20 requires the use of four sets of AES/EBU jacks: four XLR male jacks for output, and four XLR female jacks for input. The AES/EBU input jacks may be routed (or “normalled”) to multiple ADAT tracks using the M20’s INPUT ROUTING feature. The AES/EBU output jacks are always active, outputting the data from their same- numbered track, in addition to the always-active ADAT Optical outputs, so it is possible to output digital signals to several destinations simultaneously. As with all digital audio interchange formats, AES/EBU transmits audio encoded as numbers, which may only be received by another digital unit.

Do not plug any AES/EBU signals into an analog audio device (such as a microphone input). Avoid running AES/EBU signals through a patch bay or cable snake that also handles analog audio signals. Noise and improper operation may result.

The AES/EBU protocol has an embedded clock so that the transmitter and receiver can lock onto the exact same sample rate. In simple setups, this is automatic: the device receiving AES/EBU simply follows the incoming clock (for example, recording from a single CD in stereo). But in multitrack applications such as the M20, you must design your system with the “one clock” limitation in mind.

When recording multiple AES/EBU inputs, all inputs being recorded must be referenced to the same clock. For example, you cannot record into the M20 from a CD player, a DAT, and a digital sampler simultaneously, unless all of these devices are synchronous, i.e., set to use a single master word clock as their reference. For more information on setting the clock source, refer to the M20 manual chapter 15, tutorial 3 (Digital Clock Considerations).

DIGITAL AUDIO CABLES

AES/EBU is a high-frequency digital interface with some harmonics of its signal extending into the radio range. While high-quality standard microphone cables may be used, in some situations specially-designed cables may be required. Especially in long cable runs, cable with a specified impedance of 110 ohms may be required. Check with your dealer for more information.

FRONT PANEL SETUP

After installation, the EC-1 card can be selected as a digital input source and clock reference via the M20’s front panel. Input routing can be applied to the AES/EBU input as well. The AES/EBU outputs are always available, no matter what input source is selected.

EC-1 MANUAL 1.00 E-5