Audio Specs; Bundles And Audio Channels; The Conductor; Repeater Networks - Crown CTS4200 Operation Manual

CTs Multi-Channel Power Amplifi ers
8 Network and CobraNet Basics

8.2.2 Audio Specs

Sample rate: CobraNet can handle sample rates of 48 kHz or 96 kHz,
but PIP cards work only at 48 kHz. They cannot receive audio from
devices operating at 96 kHz.
Bit depth: Set each channel to transmit 16-, 20- or 24-bit audio data
as desired.
Latency: The transmitter and receiver buffering required for reliable
transmission is selectable between 1.33, 2.66 and 5.33 ms (64, 128,
and 256 samples).

8.2.3 Bundles and Audio Channels

You will be assigning all audio channels to groups called Bundles for
transmission over the CobraNet network. Bundles were formerly called
Network Channels.
A bundle can carry up to 8 audio channels. Up to eight bundles can be
sent in a 100 Mbps line, depending on the signal's bit depth and
sam pling rate.
The usual assignment is 8 channels at 20 bits. You can use fewer
channels per bundle, but maximum size bundles are suggested for the
most effi cient use of network bandwidth. If 24-bit data is desired, then
only 7 audio channels can be loaded into a single Bundle.
In System Architect, you create audio connections between sending
devices (transmitters) and receiving devices (receivers). For example, a
mixer could be a transmitter, and a power amp could be a receiver.
You assign each connection a Bundle number. The Bundle number
indicates which devices are communicating with each other.
Also in System Architect, you address each connection as Multicast or
Unicast. A Multicast (Broadcast) connection is from one transmitter
to multiple receivers. A Unicast connection is from one transmitter to
Operation Manual
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one receiver. For example, if you send a mixer's digital audio signal to
several power amps, the signal would be Multicast. Unicast is most
used on "switched" networks requiring more than 64 channels.
You specify a connection as Multicast or Unicast by the delivery
address it you give it in System Architect. 255 and lower is Multicast
(Broadcast); 256 and up is Unicast.

8.2.4 The Conductor

A CobraNet system is coordinated by one audio device in the network
called the Conductor. It regulates the CobraNet digital audio traffi c on
the CobraNet network. That is, the Conductor is the master clock for
the rest of the network.
You choose one device to be the network conductor based on a prior ity
scheme. The Conductor indicator will light on the CobraNet device
that is serving as the conductor.
The Conductor handles time-division multiplexing and clock recovery
on the network. The Conductor periodically broadcasts a well-defi ned
"beat" packet to all components to recover synchronous timing
infor mation. The "beat" also specifi es which addresses can transmit at
cer tain time slots within the "beat" period.
Each transmitting device is allowed to transmit in a given time-slot
within the Conductor-controlled isochronous cycle time. The time-slot
is determined by the assigned bundle priority. Higher bundle pri orities
receive lower-numbered positions and are transmitted fi rst.

8.2.5 Repeater Networks

CobraNet can operate on repeater networks or switched networks.
Repeater networks use low-cost Ethernet hubs. Switched networks use
network switches.
Hubs send all data packets to all connected nodes. That is, all devices
in the network receive data — even the Unicast data. Switches send
specifi c packets to specifi c devices.
Up to 8 full-loaded Bundles (64 audio channels) are allowed on a
repeater network. More Bundles may be allowed if they are loaded
with less than the full eight audio channels.
Generally, a repeater-based CobraNet network must carry only
CobraNet data to guarantee reliable transmission of audio
pack ets. Use of repeater networks is not recommended.

8.2.6 Switched Networks

A more complex CobraNet network can be built using Ethernet
switches. Switches do not simply broadcast each and every
packet to all nodes. Instead, they check each incoming data
packet to determine its destination and (very quickly) transmit the
data to only that destination port. This allows for more network
data fl ow, more Bundles and more audio channels.
In effect, each network port in an audio component has 100MB of
bandwidth. The network can be as large as 100MB times the
number of ports on the network.
Another advantage of switched networks is "full-duplex"
connec tions between components. A full-duplex link allows
simulta neous send and receive over the same Ethernet
connection.
In theory, each connection can simultaneously send and receive
up to 64 channels per node, for a total of 128 channels. However,
current CobraNet components can handle only 64 channels (32 in
and 32 out).
Switches and full-duplex connections allow up to 128 channels
per component, and greater than 3000 individual Unicast
chan nels.
Switched networks also allow controllers (such as computers) to
be on the same network as CobraNet devices.
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