Digital Signal Cabling - L-Acoustics LA4X User Manual

LA4X
Amplified Controller
user manual
VERSION 4.0
3.4.3

Digital SIGNAL cabling

The four AES/EBU XLR3 connectors on the SIGNAL panel (see Figure 7) are transformer balanced and wired
according to IEC 268.
The two female XLR3 input connectors AES/EBU IN A&B and AES/EBU IN C&D can receive up to four digital signals
(when setting the AES/EBU input mode for channel pairs AB and CD). The input format is AES/EBU (AES3) or coaxial
S/PDIF (IEC 60958 Type II).
In a daisy-chain layout, the two male XLR3 link connectors LINK A&B and LINK C&D feed the input signals to the next
amplified controller in the signal chain (see Figure 9). Each LINK connector is electronically buffered to allow daisy-
chaining any number of amplified controllers. It also features a failsafe relay to ensure wiring continuity in case of
amplified controller shutdown.
Cables for AES/EBU digital audio
The quality required for the XLR cables will depend on the cable length and the signal sampling frequency. As a
starting point, a standard balanced microphone cable of maximum length of 50 m (150 ft) can be used to
transport a signal of maximum sampling frequency of 48 kHz. Higher sampling frequencies may require reducing
the cable length since the signal attenuation in cables increases with the sampling frequency.
As AES/EBU certified cables provide smaller attenuation/length ratio, it is highly recommended to use them in
installations requiring long cable runs or high sampling frequency signals.
It is recommended to use single cuts of cable. Using several pieces will reduce performances.
In case an amplified controller shutdowns, the failsafe relay makes a passive connection between the AES/EBU
IN ports and the LINK ports to maintain continuity. However the signals are no longer refreshed for the next
amplified controller, so that the input cable and the link cable must be considered as a unique input cable with
regard to the maximum supported length.
In case of transmission losses, try to reduce the sampling frequency of the digital audio source. Moreover, as a
general rule, avoid using sources rated beyond 96 kHz as the maximum possible cable length will be reduced
while the additional information will anyway be cancelled by SRC to 96 kHz.
LA4X_UM_EN_4.0
Figure 9: Daisy-chaining digital audio
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