UK_AutoMixers_V2.doc
Rev 2.0
4
WHY AUTOMATIC MIXING IS NECESSARY
Installations with more microphones have always given several problems to audio technicians.
Using few microphones, some speakers have a clear audio, while others seem to be “far away”. If
too much microphones are used, the background noise is higher and it makes difficult listening to
the speakers.
A single speaker’s voice often reaches and is shot by more microphones and that causes a poor
audio quality. Since it is difficult choosing an exact no. of microphones to cover an area without
superimpositions, somebody should open and close microphones according to who is speaking.
This requires not only a great ability, but also a stressful quantity of work.
Use an automatic mixer.
HOW DOES AN AUTOMATIC MIXER WORK
Automatic mixing “opens” microphones when they are in use and it “softens” them when they are
not used.
Minimizing the number of simultaneously working microphones, that reduces the whole
background noise supplying a clearer and more intelligible audio.
Note: microphones opening, instead of turning on and off, gives a softer and more natural starting.
Softened microphones, even technically working, are quite “low” to seem closed.
APPLICATIONS WITH PA SYSTEMS
This kind of applications requires more than the others the automatic mixing. The ground is the
feedback, the high-frequency sound, which occasionally is heard from loudspeakers; each open
microphone increases feedback possibility. More microphones are open at the same time, more it
is likely that feedback happens; automatic mixers reduce this problem by keeping a minimum no.
of open microphones.
This unit includes a circuit (NOM) reducing of 3 dB the total gain of the system, any time the open
microphone no. doubles (i.e. from 1 to 2, from 2 to 4 and from 4 to 8); this keeps PA system under
the level in which feedback could happen.
POWER SUPPLY
The unit is expected to work with 230 VCA – 50/60Hz distribution system.
In case of power dysfunction, check the outside protection fuses (230 V~21 of fig. 1)) and
eventually replace them with others of same calibration; if one of them burns out immediately, do
not go on and have check the unit by qualified personnel.
Take away plug from 230 VCA electric power socket always, before removing fuses and, in any
case, open the unit framing.
