Crown Audio IQ P.I.P.-DSP - Manual (Page 16)

Page 16
IQ–P.I.P.–DSP Programmable Input Processor with DSP for IQ Systems
Reference Manual
4.8 Polarity Inverter
The polarity of the input signal of each channel can be
independently inverted by the
IQ System.
4.9 Input Signal Attenuator
An attenuator is available at the input of each channel
to control the input signal level. These attenuators are
controlled and monitored by the
IQ System. They may
appear to move like “flying faders” on some IQ software
screens because they reflect all reductions in gain that
are dynamically applied by the input compressor/
limiter, input protection limiter and
ODEP conservation
functions. Each input attenuator has a range from 0 dB
to –80 dB in ½ dB steps. (Zero equals no attenuation.)
Note: The IQ–P.I.P.–DSP was designed for a nominal
input level of 0 dBu. If “hot” input signals are required,
use the input signal attenuators to “pad” the input
levels.
4.10 Input Protection Limiter
The input protection limiter is not designed to be
changed by the user. It is set at the factory for minimal
interaction while providing adequate input protection.
It protects the A/D converter from an excessive input
signal. Normally there is no risk of this problem if the
unit is installed as instructed in Section 3 of this manual.
The input protection limiter operates after the input
compressor (Section 4.12) and input attenuator
(Section 4.9) of each channel. If the compressor and/
or attenuator reduce the input gain enough to prevent
distortion, the input protection limiter will do nothing.
Note: Since the input attenuators can be dynamically
monitored by the IQ System, they may appear to move
as “flying faders” on some IQ software screens to
reflect dynamic gain reductions. Moving faders while
all other dynamic processing functions are turned off,
is an indication that the input protection limiters are
activating because the gain has not been optimized.
To prevent the input protection limiters from operating,
configure the amplifier with an input sensitivity of 0.775
V and operate the amplifier with the output level
controls at full volume as described in the installation
instructions in Section 3. In this configuration the
amplifier will clip before the threshold of the input
protection limiter is exceeded.
4.11 Auto
An Auto function (Auto System Actuate or “ASA”) is
available to provide consistency with other IQ
components in the IQ System. It is controlled by the IQ
System and it serves as a toggle to quickly enable or
disable many of the functions in the
IQ–P.I.P.–DSP. The
functions that are enabled/disabled by the Auto control
are: input signal compressor/limiter, output limiter, auto
standby and
ODEP Limiter warning.
The filter and signal delay settings are not affected by
the Auto function. In the case of the filters, this can be
very important. For example, a high-frequency driver
should not be fed a full-band signal when someone
turns off the Auto control. Please refer to the
User’s
Manual for your IQ software for more information about
the Auto function.
4.12 Input Signal Compressor/Limiter
An input signal compressor/limiter is available for each
channel. Each one is controlled by the
IQ System and
has five parameters:
Input Compressor: Turns this function on/off.
Threshold: Sets the threshold, in dB, above which
the compressor acts. The level is measured at the
input to the
P.I.P. and corresponds to the level
shown on an input meter. The compressor is
“feedforward,” meaning that the level detection
point is located before the gain control stage. The
range is from +16 dBu to –40 dBu.
Attack Time: Sets the attack time of the
compressor. The attack time is defined as the time
it takes the compressor to attenuate the input
signal by 10 dB. The range is from 1 millisecond to
2 seconds.
Release Time: Sets the release time of the
compressor. The release time is defined as the
time it takes the compressor to increase the input
gain by 10 dB. The range is 100 milliseconds to 30
seconds.
Ratio: Sets the compression ratio for the
compressor. The range is 1, 2, 4, 8, 16, 32,
¥ to 1.
Note: 1:1 is the same as “off.”
4.13 Smooth/Output Signal Limiter
An output signal limiter is available for each channel.
They can be used either as “smooth” output levelers
(similar to other IQ
P.I.P.s with SmartAmp features) or
they can be used as fast output limiters to protect
drivers and other system components from large
transient signals. They follow the filter functions in the
DSP, making them frequency dependent. The output
voltage of the amplifier is limited (within ½ dB) based
on real-time sampling of the actual amplifier output. The