User manual ALESIS EC1

[. . . ] AES/EBU channel pairs can be selected as a clock source as well. E-4 EC-1 MANUAL 1. 00 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 samenumbered track, in addition to the always-active ADAT Optical outputs, so it is possible to output digital signals to several destinations simultaneously. [. . . ] Insert the ribbon connector into the 40-pin header on the main circuit board. The header is labeled "J7" and sits to the right of the chip labeled "2-32-0007 SMPTE FPGA". Screw the EC-1 card into the expansion slot from the inside of the M20. 5. To test for proper installation, plug the unit back in to AC power, turn on the M20, and press the Digital Source button (next to the meter display) until the "DIG SOURCE" group in the meter display indicates "I/O CARD". This confirms that the M20 has detected the EC-1's presence. E-6 EC-1 MANUAL 1. 00 Appendix E, EC-1 AES/EBU Interface BASIC OPERATION SELECTING AES/EBU (I/O CARD) AS THE DIGITAL SOURCE When using digital inputs, the Digital Source function selects one of three digital input options. The I/O CARD option will appear in the display only if an I/O card (such as the Alesis EC-1 card) is installed in the M20. With the EC-1 card installed, pressing the Digital Source button (next to the meter display) toggles through the available sources, such as ADAT OPTICAL, TRACK COPY, and I/O CARD. To select AES/EBU as the digital source, press the Digital Source button until I/O CARD appears in the DIG SOURCE group of the meter display. Now, when Input Select mode is set to digital input for a given channel pair (and dependent on how input routing is configured), an AES/EBU input will be the source for the selected channels. SELECTING AES/EBU (I/O CARD) AS THE CLOCK SOURCE If a word clock, video, or optical clock source that is synchronous to AES/EBU digital audio input is not available, sample clock for the M20 can be derived from any of the four AES/EBU input channel pairs. TO SELECT AES/EBU 1. 2. AS THE CLOCK SOURCE: Press the Clock Source button (under the main display) until I/O CARD appears in the CLOCK SOURCE group of the main display. When I/O Card is selected, the alpha-numeric in the main display will indicate, "AES Clk Source: Chan 1/2". This implies that the M20 will look for clock input at the channel pair 1 and 2 XLR input. If AES/EBU clock input is not detected, the I/O CARD indicator will flash and the M20's internal clock will be used until valid AES/EBU input is detected. As noted earlier, if recording multiple AES/EBU pairs, their clocks must be synchronous to avoid "ticks" and "pops" or audio distortion. If you have multiple synchronous inputs (for example, from a single digital mixer), it does not matter which channel pair is chosen as the clock source. 3. Example: Suppose you set the digital source to I/O CARD, and set the input selection for channels 3 and 4 to digital (shown by the "D" illuminated under those channel meters on the M20). Input 3/4 on the EC-1 card is the only jack connected to an AES/EBU digital audio source (like a DAT recorder). If no other AES/EBUsynchronous external clock source is available, I/O CARD must be selected as the clock source. But when you do this, the clock source I/O CARD indicator flashes, and audio monitored via the M20 is distorted. Just as the analog Input Routing feature allows you to do that with an analog input, you can do the same for AES/EBU inputs from the EC-1 card. You have the following AES/EBU routing choices when the digital source = I/O Card: · Odd/Even (2-bus feed): Press INPUT ROUTING and either the Track 1 or 2 button. Input 1 feeds channels 1, 3, 5, 7, and Input 2 feeds channels 2, 4, 6, 8. To record on an odd-numbered track, route the signal(s) to bus #1 or left. [. . . ] The scenario below describes a mixed signal input using I/O CARD as the digital source: Example: You are recording a digital submix patched into AES/EBU input pair 1/2 and intend to route this input to channels 3 and 4. You also have an analog submix patched into the analog inputs for channels 7 and 8. INPUT ROUTING uses the "odd/even" configuration (channels 1 and 2 are the digital source tracks). INPUT SELECT is set to DIGITAL input for channels 1 through 4; and ANALOG input for channels 5 through 8. [. . . ]