Interconnection Options - Lab.gruppen PLM series Operation Manual

Application Guide
The Input and Link connectors 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.
Never connect a digital signal source to an analog input or an
analog signal source to a digital input.

10.6.3.2 Interconnection Options

If multiple PLM Series devices are receiving the same AES3 signal, connections may be configured in two
ways:
1. Daisy-Chain – Connect the signal source (e.g. mixing console, digital snake or distribution amplifier)
to the AES3 input on the first PLM. Connect the adjacent Link output on the same unit to the Input
on the next PLM, and continue connecting in this manner. Up to 20 PLM units may be daisy-chained
in this manner, though the total may be dependent on environmental conditions and the quality of
connecting cables.
2. AES3 Distribution Amplifier – Connect the input of the distribution amplifier to the signal source, and
connect the outputs individually to the PLMs. The number of available outputs must be equal to or
greater than the number of PLM devices to be driven. The distribution amplifier must be specifically
designed for AES3 signals; a device made for analog signals will not function in this capacity. Please
refer to section 10.6.4 for further information.
Consider the application requirements carefully before choosing an interconnection configuration. Note that
the daisy-chain option presents a potential single-point-of-failure scenario; failure of one cable or connection
will affect all subsequent devices in the chain. Use of distribution amplifiers avoids this scenario, although
extra expense is involved and potential failure of the distribution amplifier itself is introduced.
10.6.3.3 Cable Types and Distance Limitations
All digital connections should be made with 100 ohm balanced cables wired according to the AES3
standard (see Figure 8-8 on page 65). 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 careful trials are recommended before use in the field. Sampling rate also governs
allowed cable length; a 100 meter length at 96 kHz might extend to 200 meters at 48 kHz, but be cut to
50 meters at 192 kHz.
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PLM Series Operation Manual rev 1.1.9