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Operating Manual - nX, nXe, and nXp 150W/75W Power Amplifiers
ANC Setup Procedure
1) In the control software, assign the ANC function to the channel to be used for background music or voice paging (program
audio). Set the ANC controls to the "typical" settings described above, which is also the default settings of a new ANC function
when it is first placed in the signal processing block.
2) Open the ANC control window and select the noise-sensing microphone input channel in the drop-down box labeled "Mixer
Input Channel".
3) Physically locate the noise-sensing microphone in the room by pointing it toward the noise sources such as groups of people
talking, HVAC equipment etc., and
pointed away from the sound system speakers or their direct reflections
.
4) Add microphone preamp gain (external preamp) and level control functions (software) on the noise-sensing microphone
signal path before the matrix mixer and adjust the microphone gain so that you can see the ambient noise input level meter start
to show a level when the room noise starts to increase. To adjust the ANC controls for good-sounding operation without people
present, a pink noise source or even a portable stereo can be placed near the expected noise location to simulate expected noise.
5) Adjust the ANC's noise threshold control to the ambient noise input level at which you would like the program audio gain
to start to increase. Increase the room noise source so that you see the ambient noise input level meter rise above your noise
threshold setting. You should see the program audio gain meter slowly rise above the minimum gain setting.
6) Slowly increase the noise source and adjust the program/ambient gain ratio for the desired amount of noise compensation.
7) Continue to increase the noise source to the highest level you would expect. Adjust the max gain to a level which limits the
maximum gain that the ANC applies to the program audio so it will not become too loud or clip.
8) The gain change rate can be adjusted according to how fast you would like the gain changes to take place in response to
changes in ambient noise.
9) Be aware that an improperly setup ANC can result in runaway gain where the program audio is picked-up by the noise-sensing
microphone as background noise. The result is not necessarily feedback squeals, but the gain of the program audio could ramp
up to the max gain value even with no ambient room noise. The best remedy for this problem is to locate the noise-sensing mi
-
crophone closer to the expected noise sources and further away from the sound system speakers or their reflections. Sometimes
a baffle may be helpful, located between the speaker and microphone to block direct or reflected sound pickup. Also, the ANC
program/ambient gain ratio can be lowered to reduce the susceptibility to gain runaway.
2)
Gain
Functions
Gain
The gain block allows the user to modify a signal's level by either applying gain or attenu
-
ation. The polarity of the signal may also be inverted. The level control allows for gain
adjustment b12db and -50dB and OFF. The level fader can be adjusted in 0.5dB
increments. Finer adjustment (0.1 dB increments) may be made by typing in the value into
the provided text box below the fader.
The gain block may be linked with any other gain block via Protea
ne
software. This will force
all parameters (level and polarity) to be the same across linked blocks. Note that changes
to a linked gain block do not affect a VCA gain block.
For a more powerful linking of gains, consider using the gain with VCA block.
Parameters
Level
- Off, -50dB to +12dB in 0.1dB increments
Polarity
- Normal or inverted.
