User manual M-AUDIO COW-20

[. . . ] 1 Version COW20- 080699 24 Bit Flying Cow TM MANUAL Table of Contents FCC Class B and CE Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 D/A Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] A typical configuration in which a Flying Cow would be used includes a Flying Cow, a PC based digital I/O card, a mixer and an amplifier/sound system (see Typical Setup figure). Such a configuration could be setup as follows: 1. ) the unbalanced stereo audio out of the mixer goes to the 1/4" audio inputs on the Flying Cow, 2. ) the S/PDIF out of the digital audio card goes to the S/PDIF In on the Flying Cow, 3. ) the S/PDIF in of the digital audio card goes to the S/PDIF Out on the Flying Cow, 4. ) the unbalanced Analog Out on the Flying Cow goes to a line level audio in on the amplifier/sound system. 8 Typical Setup - Fig. The D/A converter receives a continuous digital audio stream from either the AES/EBU In or S/PDIF In jack, depending on the setting of the Digital Format on the Flying Cow's front panel. The digital data is converted to stereo analog audio, and output through the left and right Analog Out jacks. The Analog Out jacks can accept either XLR connections or 1/4" connections. On the XLR audio out connections, the audio is balanced; on the 1/4" audio out connections, the audio is unbalanced. Instead, it automatically detects the sample rate of the incoming digital audio data and adjusts it accordingly. If a valid digital stream is detected, the front panel "D/A Valid" LED will light. 10 IMPORTANT: For the Flying Cow D/A converter to work properly, the Digital Format must be set to the correct incoming digital format (AES/EBU or S/PDIF). A/D Operation The Flying Cow A/D converter accepts analog audio from the left and right Analog In jacks, using either XLR or 1/4" connections. The 1/4" audio input connections accept either balanced (tip-ringsleeve) or unbalanced (tip-sleeve) signals. The analog signals then pass through the Analog Input Level control and into the A/D converter as balanced signals. Finally, the A/D converter converts the analog data to a digital data stream and outputs it to both the AES/EBU Out and S/PDIF Out jacks simultaneously. IMPORTANT: The same digital data is always present at both the AES/EBU and S/PDIF output jacks. However, the data format of the audio stream will be correct on one jack but not the other (the data format will match the Flying Cow's front panel Digital Format setting). However, if it does, you must set the front panel Digital Format to match the digital output standard you will be using. The A/D converter requires three parameters to be set up for proper operation: Digital Format, Input Level, and Sample Rate. From the front panel controls of the Flying Cow, set the Digital Format to match that of the digital output jack of the external equipment to which you are connecting the Flying Cow (see page 10­Selecting Modes). For example, if you are connecting the Flying Cow S/PDIF Out to the S/PDIF In of a PC digital sound card, set the Digital Format to S/PDIF. For best conversion, the input signal should have enough amplitude to take advantage of all 24 bits of A/D resolution. In other words, the incoming audio signal should be loud enough to approach the A/D converter's maximum acceptable (full-scale) signal level. The Analog Input Level adjustment on the Flying Cow's front panel allows you to attenuate or amplify an incoming signal to properly attain the optimum A/D input level. The Flying Cow 11 front panel A/D Input Level indicators aid in this adjustment. [. . . ] Finally, listen to the Analog Out signals and verify that it matches the known incoming signals with no discernible distortion. 17 Appendix C - Block Diagram LEFT ANALOG INPUT XLR 1/4" ANALOG INPUT LEVEL LED Ladder AES/ EBU S/P DIF Digital Format (changed by Mode Select Switch) Mode Select Switch DIGITAL OUTPUTS AES/EBU RIGHT ANALOG INPUT XLR A/D CONVERTER S/PDIF ANALOG INPUT LEVEL LED Ladder Mode Select Switch 1/4" A/D Sample Rate 48 44. 1 32 Ext (changed by Mode Select Switch) Extracted Clock LEFT ANALOG OUTPUT XLR DIGITAL INPUTS AES/EBU AES/ EBU Mode Select Switch S/PDIF S/P DIF D/A CONVERTER 1/4" Digital Format (changed by Mode Select Switch) RIGHT ANALOG OUTPUT XLR 1/4" 18 Appendix D - Grounding Grounding the shield of a digital cable can sometimes be a tricky issue. In the configuration of audio systems, it is important to avoid ground loops and DC current flowing down the shield of the cable that could result when boxes with different ground potentials are connected. Generally, it is good practice to ground the shield to the chassis of the transmitting unit, and connect the shield through a capacitor to chassis ground at the receiver. This is how the Flying Cow is factory configured and should work fine with most systems. [. . . ]