Generally, the AUX3 channel is used as monitor bus. Depending on the setting of the AUX3 POST
switch, it is also possible to configure the bus for the connection of an additional, external FX unit.
33. AUX3 SEND
This output is meant for the connection of an external FX unit, a power amplifier or active stage
monitor speaker systems, when the AUX3 bus is used for monitoring purposes. Using the AUX3
fader, the output level can be adjusted in a wide range up to +20dBu. The AUX3 send is designed
in Ground Sensing technology to prevent the induction of external noise, even when longer cables
are involved.
34. FEEDBACK FILTER
The feedback filter is a very narrow banded notch filter which is only active in a range that is
extremely susceptible for acoustical feedback. The frequency band is set, using the corresponding
rotary control. The filter is activated by pressing the corresponding ON switch. Acoustical feedback
is originated when the amplification rate in a signal loop, consisting of microphone, amplifier, and
loudspeaker systems, and regarding its phase coherence and the distance between speakers and
microphone, is not clearly negative. Or in other words: the speaker signal hits the microphone and
gets amplified again, resulting in an escalating oscillation, which is audible as high pitched whistle
or loud humming sound. However, explaining all factors that are relevant for the occurrence of
feedback would lead to far. The following notes are meant to assist you in avoiding feedback and
you should take them into consideration even before you activate the feedback filter.
1.Do not position the main speaker systems behind the microphones.
2.Turn off all unused microphones.
3.Also consider the microphones’ different polar patterns and characteristics, when placing
the monitor speakers.
4.Do not turn up the monitor system’s volume higher than really necessary.
5.Try to avoid extensive equalization on channels that you want to include in your monitor mix.
6.Keep in mind, that microphones “behave” different when somebody stands right in front of them.
In fact, the amount and intensity of first reflections changes drastically.
7.Position the microphones as direct as possible to the sound source.
If you still have the feeling that the monitor system’s volume is not high enough, after considering
the above mentioned precautions, you can use the feedback filter to mute the frequency that tends
to generate feedback the most. Therefore, you have to perform the following steps:
Increase the AUX3 (monitor) level until the limit where feedback starts. The “sound” you hear is
generated within the system. Turn on the feedback filter and adjust the rotary control at the mark
where the “sound” disappears. Switching the filter on and off lets you easily check if you tuned in
the correct frequency. The feedback filter attenuates the corresponding frequency band by about
9dB. Since the filtered band is extremely narrow, an alteration in the sound of your monitor system
is hardly audible.
CAUTION: Please be extremely careful when you increase the level up to the feedback limit.
Careless operation, resulting in feedback noise at high SPL, can severely damage your speaker
systems and – even more important – the human ear.
35. AUX3 POST
As mentioned before, this switch is used to determine if the AUX3-mix signal is PRE or POST
FADER. In case the switch is engaged and the yellow LED lights, the signals of all AUX3 controls
in the input channels are split post their corresponding channel faders.
36. PFL
Through this button you can route the pre AUX3 fader signal to the headphones bus. The signal
is outputted via the headphones output. The setting of the AUX3 fader is not relevant for the signal’s
volume (PRE FADER LISTEN), leaving you with the opportunity to adjust its level and equalization
without the need to route it to the AUX3 SEND bus.
37. AUX3 VOLUME
This fader controls the AUX3 SEND output level. So when the AUX3 bus is used for monitoring,
this fader lets you control the volume of the monitor system.
AUX 342