Manual
10. Application Guide
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PLM+ SERIES Operation Manual rev 1.0.0
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
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
careful trials are recommended before use in the eld. 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.
10.6.3.4. 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.
As a precautionary measure four touring applications, it is advisable to congure all digital audio wiring prior to use.
It is recommended that all cables be tested for error-free performance at lengths 20% to 25% greater than lengths
to be used in the eld in order to provide a comfortable margin of safety.
10.6.4. External Signal Distribution Hardware
10.6.4.1. Distribution Amplifiers
Dedicated distribution ampliers for AES3 signals are available from several manufacturers. The most common
format is one input and six outputs. Digital distribution ampliers are designed to refresh or reconstruct the signal
as well making up for line losses.
One type of distribution amplier is a simple repeater, which restores the waveform shape and brings the signal
amplitude back up the required level. Some distribution ampliers also offer a re-clocking feature, which also re-
times the signal to prevent signal degradation from clocking errors known as jitter.
Distribution ampliers that offer re-clocking often make the feature optional as using re-clocking can introduce
small additional amounts of latency, so should not be used unless necessary.
10.6.4.2. Passive splitters
One single AES3 input may be split into more signals using a simple passive splitter. Splitters provide a convenient
and low cost solution when only a few additional signals are required, and in situations where cable lengths are
short. Attenuation is minimal, but there is no refreshing of the signal.