Lab.gruppen PLM 20K44 Operation Manual page 84

10. Application Guide
10.5.3. Connections and Cabling
10.5.3.1. AES Input Connectors
Two AES-3 input signals (each carrying two audio channels) are connected to the XLR3F connectors labelled
INPUT 1-2 and INPUT 3-4 in the AES/EBU (AES-3) input section on the rear panel. Note that the Input connector
types are identical for the analog and digital inputs, so care must be taken when connecting audio, particularly
when analog inputs are used as a backup signal source. Connectors should be clearly labeled to prevent any
confusion.
NOTE: Never connect a digital signal source to an analog input or an analog signal source to a digital
input.
10.5.3.2. Interconnection of Multiple Units
The AES implementation in PLM+ is designed to be able to daisy-chain AES signals using passive Y-Split cables.
The PLM+ device at the end of a distribution line should be set to TERMINATED; all other PLM+ devices should be
with one DA output per processor, then all terminations should be on. However, if the AES3 is daisy-chained, only
terminate the last processor in the chain.
Please refer to section 10.5.4 for further information.
10.5.3.3. Cable Types and Distance Limitations
All digital connections should be made with 100 ohm balanced cables wired according to the AES3 standard (see
section 8.2.2). Although standard analog microphone cabling may function in limited circumstances, the potential
for problems is greatly increased. AES3 contains a high-speed data stream, and requires an effective bandwidth of
up to 12 MHz, far beyond the 20 kHz required for analog audio.
The distance allowed between a signal source and the PLM+ is dependent on both cable quality and the sampling
rate used. At a 96 kHz sampling rate, any good quality AES3 cable should allow a cable run of 100 meters with no
data losses beyond the capability of internal error correction. The best cables may allow longer cable runs, though
meter length at 96 kHz might extend to 200 meters at 48 kHz, but be cut to 50 meters at 192 kHz.
10.5.3.4. Signal Degradation and Loss
A weak or degraded AES3 signal will exhibit no audible loss of quality as long as the robustness of the data stream
remains above the threshold required for internal error correction. As degradation approaches the threshold,
audible artifacts may be heard, including pops, clicks and momentary dropouts. Any such indications require
immediate attention, as often the window of acceptable data loss between artifacts and complete audio loss can
be very narrow.
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PLM+ SERIES Operation Manual rev 3.0.1