Crown CTS4200 Operation Manual page 17

CTs Multi-Channel Power Amplifi ers
3 Operation
(continued)
3.2.23 Input Signal Compressor/Limiter
An input signal compressor/limiter is available for each channel.
Five parameters control this feature:
Enable: Enables or disables this function.
Threshold: Sets the level, in dBu, above which the compressor
begins to attenuate the input signal. This level corresponds to the
input level meter reading. The compressor is "feed-forward,"
meaning that the level detection point is located before the gain
control stage. The range is from +20 dBu to – 50 dBu.
Attack Time: Sets the attack time of the compressor. The attack
time is defi ned as the time it takes the compressor to attenuate the
signal gain by 20 dB. The range is from 1 millisecond to 0.1
second.
Release Time: Sets the release time of the compressor. The
release time is defi ned as the time it takes the compressor to
increase the signal gain by 20 dB. The range is from 10
millisec onds to 10 seconds.
Compression Ratio: Sets the compression ratio of the
com pressor. The ratio is the relation between the amount of
attenua tion applied by the compressor verses the amount that the
input signal is over the threshold. The available settings are 2:1 to
32:1.
3.2.24 Peak Voltage Limiter
This limits the peak voltage output of the amplifi er. Four
parame ters control this limiter for each channel:
Enable: Enables or disables this function.
Threshold: Sets the level, in absolute voltage, which the limiter
will allow from the amplifi er. The range is from 12 V
Attack Time: Sets the attack time of the limiter. The attack time is
defi ned as the time it takes the limiter to attenuate the output
signal by 20 dB. The range is from 1 millisecond to 100
millisec onds.
Operation Manual
Release Time: Sets the release time of the compressor. The
release time is defi ned as the time it takes the limiter to increase
the output signal by 20 dB. The range is from 10 milliseconds to
10 seconds.
3.2.25 RMS Power Limiter
This limits the long-term output power of the amplifi er. Four
parameters control this limiter for each channel:
Enable: Enables or disables this limiter.
Threshold: Sets the average power level, in watts, which the
limiter will allow from the amplifi er channel. The range is from 10
watts to 600 watts. This level should be set to the connected
loudspeaker's long-term power rating.
Attack Time: Sets the attack time of the limiter. The attack time is
defi ned as the time it takes the limiter to attenuate the output
signal by 20 dB. The range is from 1 second to 30 seconds.
Release Time: Sets the release time of the compressor. The
release time is defi ned as the time it takes the limiter to increase
the output signal by 20 dB. The range is from 1 second to 30
sec onds.
3.2.26 Load Supervision
The load supervision feature allows real-time monitoring of the
load connected to each amplifi er channel. When enabled, the
USP/CN continuously monitors the amplifi er output voltage and
current, and calculates the long-term average load impedance.
The measured load impedance is compared against the user-
defi ned high and low limits. If either limit is exceeded, the status
indicator and, if enabled, the System Architect Error Reporting
functions alert the user of the problem. There are six controls and
two indicators for each channel:
to 255 V
pk pk.
Enable: Enables or disables the load-supervision function.
High Limit: Sets the upper bound above which the system will
report a "high" error status.
Low Limit: Sets the lower bound below which the system will
report a "low" error status.
Nominal Load Impedance: Sets the expected average
imped ance for the connected load. This value determines the
output signal level required for the test. This parameter is also
used by the average power limiter to determine the expected
power threshold. (See Section 3.1.29).
Report Error to Network: Enables Error Reporting to send an
error report via the network so that high and low load conditions
are reported to the software.
Report Error to Aux: Enables and high or low load error to be
reported by the AUX output. (See Section 4.1.1).
Test Indicator: This indicator is active when the amplifi er out put
signal is suffi cient to allow load impedance calculation and test
verifi cation.
Low/Normal/High Indicator: This indicator shows the present
status of the load impedance with respect to the user-defi ned high
and low limits.
Z Average Monitor: Reports the actual calculated average load
impedance in ohms. Its range is from 0 ohms to 250 ohms.
Load Supervision Applications
The Load Supervision feature can be used to monitor the ampli fi er
load in real time with almost any program material. Average load
impedance is calculated as a function of amplifi er output voltage
and current. The system requires approximately 20-30 mA of
average amplifi er output current for adequate supervision. This
allows typically low average output power levels of less than ½
watt with most loads. The maximum load impedance for reli able
system performance is limited to about 50 ohms. Higher
impedances can be measured but may require higher amplifi er
output levels for reliable operation.
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