L-Acoustics LA4X, Руководство пользователя

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Technical description
Signal processing and amplication
Signal inputs
The LA4X features four input connectors allowing it to receive four analog signals, four digital signals, or two analog and
two digital signals, depending on the input mode selected by the user — see section XLR INPUT MODE (p.44). This
architecture also allows digital-to-analog or digital-to-digital fallback.
In addition, four channels may be retrieved from an AVB stream containing up to eight channels at 48 kHz or 96 kHz,
connected by one of the two 1 Gb/s Ethernet ports (on compatible LA4X).
Analog
LA4X can be fed with up to four balanced analog audio signals using XLR female input connectors ANALOG IN A to
ANALOG IN D — see illustration in section Front and rear panels (p.12). Each analog input port is ESD protected.
The analog input panel also features four XLR male link connectors passively wired to the input connectors. The link
connectors allow transmitting the input signals to daisy-chained amplied controllers. Each analog link port is ESD
protected.
To be processed by the DSP, the analog signal must be converted into a digital signal. For this purpose, the LA4X
amplied controller is tted with two cascaded 24-bit A/D converters with a sampling rate of 96 kHz allowing an
encoding dynamic range of 128 dB.
AES/EBU
LA4X can be fed with up to four AES/EBU digital audio signals (transported in pairs) using XLR input connectors AES/
EBU IN A&B and AES/EBU IN C&D.
Each AES/EBU input port is an XLR female connector. The audio signals can come from a digital mixing desk or a
digital audio network bridge compliant with the AES/EBU (AES3) or electrical S/PDIF (IEC 60958 Type II) digital audio
standards. Each AES/EBU input port is ESD protected and transformer balanced.
The AES/EBU input panel also features two XLR male link ports actively connected to the input ports (with failsafe relay
in case of mains absence). The link connectors allow transmitting the input signals to daisy-chained amplied controllers.
Each AES/EBU link port is ESD protected and transformer balanced.
Each AES/EBU input port is equipped with a SRC (Sample Rate Converter) that has been selected to support a wide
range of input formats (16 - 24 bits / 44.1 - 192 kHz). The SRC converts the formats to the 24 bits/96 kHz internal
format used by the amplied controller. The SRC is a high-quality hardware component (140 dB dynamic range,
THD+N < -120 dBFS, strong input jitter attenuation) and provides constant propagation delay regardless of the input
sampling frequency.
There is no external synchronization mode. The amplied controller's clock runs using its high-precision internal quartz at
96 kHz (or on the clock of the connected AVB input stream on compatible LA4X). This ensures low jitter and high audio
quality in live conditions (large cable lengths, large number of amplied controllers) while preventing phase shift, as
required for line source systems.
Digital domain benets
Keeping the signal in the digital domain provides the following benets (with any digital mixing desk or any audio
network) compared to the analog signal distribution:
• Better audio quality by removing one D/A - A/D cycle.
• Optimized level chain by removing the risk of level misalignment between console and amplied controllers.
• Digital signal refreshed at each amplied controller in a daisy-chain.
• Improved maximum cable length. LA4X has been tested with up to 305 m/1000 ft of 3 models of AES/EBU rated
cables (single cuts, digital source signal running at Fs = 48 kHz):
• 1696A from BELDEN INC.
• OT234H from KLOTZ communications GmbH.
• SC-BINARY 234 from SOMMER CABLE GmbH.
AVB
• LA4X amplied controllers with HARDWARE INFO
ID1
,
ID2
or
ID3
(in MONITORING & INFO menu) do not
support AVB. These Units can be upgraded to support AVB by purchasing and installing KR LA4XDSP2.
LA4X owner's manual (EN) version 14.1 13