Metric Halo 3d Upgrade Board Set, Руководство пользователя

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2882 Users Guide
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first four “ADAT” channels is placed on pairs of optical channels. ADAT 1 is placed on optical channels
1 and 2. Each optical channel continues to transmit data at 1x speeds, and both devices are required to
multiplex and demultiplex the audio into and out of the optical channel pairs.
Since the 2882 provides direct routing within the box, you can easily configure the unit to work as an
ADAT based 8 channel A/D/A. Refer to the chapter on MIOConsole3d for information about configuring
the routing.
Clock Sync
Clock sync is a serious consideration in any digital audio system. The 2882 and any of it's digital audio
interfaces can be used as the master clock source either for the 2882 by itself or for a full daisy-chained
MHLink domain. In this regard, all 3d-equipped Metric Halo boxes are equal - only the physical I/O com-
plement differentiates the box models.
If you are recording analog sources with 2882 by itself or as the root box of an MHLink domain, you can
simply use the next-generation 3d internal clock source to drive the converters. This is the easiest case
to deal with.
If you need to interface with other devices digitally or ensure sample accurate sync with video sources,
the extensive clock synchronization capabilities of the 3d 2882 will prove to be more reliable (and better
sounding) than much higher priced alternatives.
There are four different ways to get external clock information into the unit:
1. Sending a word clock signal into the WC Input BNC.
2. Sending an AES signal into the XLR Digital input.
3. Sending an S/PDIF signal into the RCA Digital input.
4. Sending an ADAT or S/PDIF signal into the Optical Digital input.
The BNC word clock input port is a 75 Ohm terminated coaxial input. It should be driven by a 75 Ohm
source driver and interconnected with 75 Ohm coaxial cable. Even though the clock recovery qualities of
the 3d hardware are second-to-none, incorrect cable impedance will introduce reflections on the word
clock cable (jitter) which may adversely affect clock stability and audio quality.
The AES recommended procedure for distributing clock is to use an AES clock signal. The AES clock signal
is an AES digital audio signal with no audio activity. 2882 only uses the AES preambles for clock recovery,
so it is immune to data dependent jitter effects. This rule applies to both the XLR AES and RCA digital
inputs, which means you can reliably use the Digital Inputs as a clock sources with or without audio data.
The Optical input port will automatically adjust to any ADAT or TOSLINK signal it recieves at whatever
sample rate. For example, incoming ADAT data SMUXed at 96kHz will be decoded automatically as 4
channels of audio clocked at 96kHz requiring no adjustments from the user. That said, ADAT/TOSLINK
optical connections are generally more susceptible to jitter artifacts than copper AES, S/PDIF or word clock
sources.
Power
One of 2882’s great strengths is the flexibility of its power system. 2882 can be powered from any DC
source in the range of 9V to 30V as long as it provides 12 Watts of power. The DC input on the 2882 is a
2.1mm coaxial power connector, center positive. So if you are powering the unit with a third party power
source and it supplies 9V, the power source will have to provide 1.4 amps of current. If you are powering
the unit with 12V, the power source will have to provide 1 amp of current, and so on.