Operation Manual
I-Tech HD Series
Power Amplifiers
page 52
I-Tech HD Series
Power Amplifiers
Operation Manual
page 53
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
indi cates which devices are communicating with each other.
Also in System Architect, you address each connection as
Multi-
cast
or
Unicast
. A Multicast (Broadcast) connection is from one
trans mitter to multiple receivers. A Unicast connection is from one
transmitter to one receiver. For example, if you send a mixer’s digital
audio signal to sev eral 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.
The “Receiver Count” monitor indicates how many devices are
receiving the digital audio bundle. The “Active” indicator indicates
whether the par ticular Bundle is being actively transmitted onto the
network.
9.2.4 The Conductor
A CobraNet system is coordinated by one audio device in the network
called the
Conductor
. It regulates the CobraNet digital audio traffic
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
priority 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-defined
“beat” packet to all components to recover synchronous timing
information. The “beat” also specifies which addresses can transmit
at certain 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 deter mined by the assigned bundle priority. Higher bundle
priorities receive lower-numbered positions and are transmitted first.
9.2.5 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 flow, more
Bundles and more audio channels.
In effect, each network port in an audio component has 100MB of
band width. The network can be as large as 100MB times the number
of ports on the network.
Another advantage of switched networks is “full-duplex” connections
between components. A full-duplex link allows simultaneous send
and receive over the same Ethernet connection.
9 Appendix B: Setting Sensitivity for Best Gain Staging
Optimized system gain structure maximizes signal to noise within the sys tem.
Adjusting your amplifier to fit within an optimized system gain struc ture is
accomplished by properly setting both the sensitivity and attenuation controls
within the amplifier. I-Tech amplifiers offer 149 sensi tivity and gain settings
allowing very fine adjustment of the amplifier’s gain and voltage sensitivity.
The Appendix section of the I-Tech Application guide (online at www.
crownaudio.com) provides charts with sensitivity in volts and gain in dB for
each sensitivity/gain setting.
With other amplifiers, it is often necessary to apply attenuation in order to
achieve the desired sound pressure level. Large amounts of attenuation are not
necessary with I-Tech amplifiers and can, in fact, degrade performance. The
attenuation adjustment should only be used for small (3 dB) or tempo rary
adjustments in amplifier gain. Instead, set the sensitivity/gain of your I-Tech
amplifier so that you can achieve the desired output with the attenu ators at or
near 0 dB.
Example: Suppose that you are using an I-T9000HD with the sensitivity/gain
set at 1.4V/37.1 dB. After optimizing the gain structure of the rest of your
system you find that attenuating the amplifier by 10 dB produces the desired
loudness. The same output level, with improved signal-to-noise ratio and
headroom, can be achieved by using 0 dB of attenuation and by setting the
amplifier sensitivity/gain to 5.81V/27.0 dB (37 dB – 10 dB = 27 dB).
Note: as indicated in the online appendix, the list of possible sensitivity
settings is different for each position of the max input setting. If, while
adjusting sensitivity/gain in your amplifier, you do not find the setting you
need, try changing the status of the max input setting and search again.
Содержание I-T12000 HD
Страница 31: ......
