User manual ALESIS EC1

[. . . ] Once connected, the M20 will detect the card's presence thereby allowing digital audio I/O configurations using AES/EBU as the digital audio source with digital input routing. 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 blue side of the cable should face the front of the M20. Screw the EC-1 card into the expansion slot from the inside of the M20. Use the four screws that held the blank panel in place. 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. To select the AES clock source, use the Up/Down arrows on the keypad. The selections are Chan 1/2, Chan 3/4, Chan 5/6, or Chan 7/8. 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. Because there still is not a valid clock. The M20's default AES/EBU clock source is channel pair 1/2. [. . . ] The M20 is configured as follows: The DIGITAL SOURCE is I/O CARD. 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. Channels 3, 4, 7 and 8 are input enabled. [. . . ]